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Associating Communities with Static and Aggregate Routes
In This Chapter
This section provides information about associating communities with static and aggregate routes configurations.
Topics in this section include:
Applicability
This example is applicable to all the 7750 SR, 7450 ESS in mixed-mode and 7950 XRS series and was tested on release 12.0.R1. There are no pre-requisites for this configuration.
 
Introduction
Border Gateway Protocol (BGP) Communities are optional, transitive attributes attached to BGP route prefixes to carry additional information about that route prefix. A number of route prefixes can have the same community attached such that it can be matched by a route policy. As a result, the presence of a community value can be used to influence and control route policy.
A BGP community is a 32-bit value that is written as two separate 16 bit numbers separated by a colon. The first number usually represents the Autonomous System (AS) number that defines or originates the community whilst the second is set by the network administrator.
Knowledge of RFC 4271 (BGP-4) and RFC 1997 (BGP Communities Attribute) is assumed throughout this document, as well as knowledge of Multi-Protocol BGP (MP-BGP) and RFC 4364 (BGP/MPLS IP VPNs).
Overview
Figure 280: Network Topology
The network topology is displayed in Figure 280. The setup uses 7750/7450/7710 Service Router (SR) nodes. PE-1 to PE-4 and the Route Reflector (RR-1) are located in the same Autonomous System (AS); AS6696. CE-3 is in a separate AS 64497 and peers using eBGP with its directly connected neighbor, PE-4.
The objectives are:
The following configuration tasks should be completed as a pre-requisite:
 
Associating Communities with Static and Aggregate Routes
It is possible to add a single community value to a static and aggregate route without using a router policy.
The community value can be in the 4-byte format comprising of a 2-byte AS value, followed by a 2 byte decimal value, separated by a colon. It can also be the name of a well-know standard community; no-export, no-advertise, no-export-subconfed.
Any community added can be matched using a route policy.
The purpose of this example is to provision static and aggregate IPv4 route prefixes and associate a community with each route. These routes are then redistributed into the BGP protocol and advertised to other BGP speakers.
This is shown for IPv4 routes within a VPRN. Well-known, standard communities will also be configured to show that the correct behavior is observed.
Configuration
The first step is to configure an iBGP session between each of the PEs and the Route Reflector (RR). The address family negotiated between peers is vpn-ipv4.
The configuration for PE-1 is:
configure router bgp    
     group internal
         family vpn-ipv4 
         type internal
         neighbor 192.0.2.20
         exit         
     exit
exit all        
 
The configuration for the other PEs is very similar. The IP addresses can be derived from Figure 280.
The configuration for the RR is:
configure router bgp 
     cluster 0.0.0.1   
     group rr_clients 
		type internal                    
		family vpn-ipv4 
             neighbor 192.0.2.1
             exit
             neighbor 192.0.2.2
             exit 
             neighbor 192.0.2.3
             exit 
             neighbor 192.0.2.4
             exit             
         exit
exit all
 
On RR-1, show that BGP sessions with each PE are established, and have correctly negotiated the VPN IPv4 address family capability.
A:RR-1# show router bgp summary 
===============================================================================
 BGP Router ID:192.0.2.20       AS:64496       Local AS:64496      
===============================================================================
BGP Admin State         : Up          BGP Oper State              : Up
Total Peer Groups       : 1           Total Peers                 : 4         
Total BGP Paths         : 18          Total Path Memory           : 3336      
Total IPv4 Remote Rts   : 0           Total IPv4 Rem. Active Rts  : 0         
Total McIPv4 Remote Rts : 0           Total McIPv4 Rem. Active Rts: 0         
Total McIPv6 Remote Rts : 0           Total McIPv6 Rem. Active Rts: 0         
Total IPv6 Remote Rts   : 0           Total IPv6 Rem. Active Rts  : 0         
Total IPv4 Backup Rts   : 0           Total IPv6 Backup Rts       : 0         
 
Total Supressed Rts     : 0           Total Hist. Rts             : 0         
Total Decay Rts         : 0         
 
Total VPN Peer Groups   : 0           Total VPN Peers             : 0         
Total VPN Local Rts     : 0         
Total VPN-IPv4 Rem. Rts : 8           Total VPN-IPv4 Rem. Act. Rts: 0         
Total VPN-IPv6 Rem. Rts : 0           Total VPN-IPv6 Rem. Act. Rts: 0         
Total VPN-IPv4 Bkup Rts : 0           Total VPN-IPv6 Bkup Rts     : 0         
 
Total VPN Supp. Rts     : 0           Total VPN Hist. Rts         : 0         
Total VPN Decay Rts     : 0         
 
Total L2-VPN Rem. Rts   : 0           Total L2VPN Rem. Act. Rts   : 0         
Total MVPN-IPv4 Rem Rts : 0           Total MVPN-IPv4 Rem Act Rts : 0         
Total MDT-SAFI Rem Rts  : 0           Total MDT-SAFI Rem Act Rts  : 0         
Total MSPW Rem Rts      : 0           Total MSPW Rem Act Rts      : 0         
Total RouteTgt Rem Rts  : 0           Total RouteTgt Rem Act Rts  : 0         
Total McVpnIPv4 Rem Rts : 0           Total McVpnIPv4 Rem Act Rts : 0         
Total MVPN-IPv6 Rem Rts : 0           Total MVPN-IPv6 Rem Act Rts : 0         
Total EVPN Rem Rts      : 0           Total EVPN Rem Act Rts      : 0         
Total FlowIpv4 Rem Rts  : 0           Total FlowIpv4 Rem Act Rts  : 0         
Total FlowIpv6 Rem Rts  : 0           Total FlowIpv6 Rem Act Rts  : 0 
===============================================================================
BGP Summary
===============================================================================
Neighbor
                   AS PktRcvd InQ  Up/Down   State|Rcv/Act/Sent (Addr Family)
                      PktSent OutQ
-------------------------------------------------------------------------------
192.0.2.1
                64496    2089    0 17h20m25s 7/0/8 (VpnIPv4)
                         2091    0           
192.0.2.2
                64496    2083    0 17h20m16s 0/0/8 (VpnIPv4)
                         2091    0           
192.0.2.3
                64496    2082    0 17h19m44s 0/0/8 (VpnIPv4)
                         2089    0           
192.0.2.4
                64496    2084    0 17h20m19s 1/0/8 (VpnIPv4)
                         2091    0           
-------------------------------------------------------------------------------
A:RR-1#
 
VPRN: IPv4
Figure 281: CE Connections for Next-Hops
The VPRN configuration for PE-1 is shown below:
A:PE-1# configure service vprn 3 
----------------------------------------------
            route-distinguisher 64496:3
            auto-bind ldp
            vrf-target target:64496:3
            interface "int-PE-1-CE-1" create
                address 172.16.1.1/30
                sap 1/2/1:1.0 create
                exit
            exit
            interface "int-PE-1-CE-2" create
                unnumbered "loop1"
                sap 1/2/2:1.0 create
                exit
            exit
            interface "loop1" create
                address 192.0.2.100/32
                loopback
            exit
 
LDP is used as the label-switching protocol for next-hop resolution.
The configuration is very similar for the other PEs.
PE-4 is configured with an interface towards CE-3 that supports eBGP, as follows:
A:PE-4# configure service vprn 3 
A:PE-4>config>service>vprn# info 
----------------------------------------------
            autonomous-system 64496
            route-distinguisher 64496:3
            auto-bind ldp
            vrf-target target:64496:3
            interface "int-PE-4-CE-3" create
                address 172.16.0.1/30
                sap 1/1/4:3 create
                exit
            exit
            bgp
                export "PE-4-VPN-BGP" 
                group "VPRN-3-ext"
                    peer-as 64497
                    neighbor 172.16.0.2
                    exit
                exit
                no shutdown
            exit
            no shutdown
 
Static Routes with Communities
A static route has a number of next-hop options – direct connected IP address, black-hole, indirect IP address and interface-name.
Figure 281 shows a pair of Customer Edge (CE) routers connected to PE1. The link to CE-1 is a numbered link. The link to CE-2 is an un-numbered link. The loopback interface address is used as a reference address for the un-numbered Ethernet interface.
Beyond CE-1 are a number of /24 subnets. Static routes to these individual subnets are created on PE-1 using a static route with a next-hop type of “interface address” or an “indirect address”. The indirect address is learned using a static route.
Beyond CE-2 is a single /24 subnet. A static route to this subnet is created using an interface-name next-hop type.
There are a number of well-known, standard communities:
The requirement for each subnet is
A:PE-1>config>service vprn 3
        static-route 10.100.100.0/24 next-hop 172.16.1.2 community no-export
 
A:PE-1>config> service vprn 3
        static-route 10.100.101.0/24 next-hop 172.16.1.2 community 64496:101
 
10.100.102.0/24 must not be advertised to any BGP peer. This must be associated with the standard, well-known community no-advertise. The community value is encoded as 65535:65282 (0xFFFFFF02), but the CLI requires the keyword no-advertise.
 
A:PE-1>config> service vprn 3
        static-route 10.100.102.0/24 next-hop 172.16.1.2 community no-advertise
 
 
A:PE-1>config> service vprn 3
        static-route 10.100.103.0/24 next-hop 172.16.1.2 tag 10 community 64496:103
 
 
A:PE-1>config> service vprn 3
        static-route 10.100.104.0/24 indirect 192.0.2.21 community 64496:104
        static-route 192.0.2.21/32 next-hop 172.16.1.2 community no-advertise
 
 
A:PE-1>config> service vprn 3
        static-route 10.100.105.0/24 next-hop "int-PE-1-CE-2" community 64496:105
 
On PE-1 configure static routes that match the static routes from Figure 281, and the conditions from above.
Note that the default behavior of a VPRN is to export all static and connected routes into a BGP labelled route with the appropriate route-target extended community configured in the vrf-target statement. A single community string can be added using the static-route community commands shown above. If multiple communities are required, then a VRF-export policy should be used. This is outside the scope of this note.
Examine the BGP table of PE-1 to establish that routes have been exported correctly in VPN IPv4 towards RR-1.
A:PE-1# show router bgp neighbor 192.0.2.20 advertised-routes vpn-ipv4 
===============================================================================
 BGP Router ID:192.0.2.1        AS:64496       Local AS:64496      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
 
===============================================================================
BGP VPN-IPv4 Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop                                            Path-Id     Label
      As-Path                                                        
-------------------------------------------------------------------------------
i     64496:3:10.100.100.0/24                            100         None
      192.0.2.1                                          None        262142
      No As-Path                                                      
i     64496:3:10.100.101.0/24                            100         None
      192.0.2.1                                          None        262142
      No As-Path                                                      
i     64496:3:10.100.103.0/24                            100         None
      192.0.2.1                                          None        262142
      No As-Path                                                      
i     64496:3:10.100.104.0/24                            100         None
      192.0.2.1                                          None        262142
      No As-Path                                                      
i     64496:3:10.100.105.0/24                            100         None
      192.0.2.1                                          None        262142
      No As-Path                                                      
i     64496:3:172.16.1.0/30                              100         None
      192.0.2.1                                          None        262142
      No As-Path                                                      
i     64496:3:192.0.2.100/32                             100         None
      192.0.2.1                                          None        262142
      No As-Path                                                      
-------------------------------------------------------------------------------
Routes : 7
===============================================================================
A:PE-1#
 
Note that there are only seven exported routes. The route prefixes associated with the no-advertise community are not present, as expected.
Examining the BGP table of PE-4 shows the presence of the expected routes, with the correct community values.
The prefix 10.100.100.0/24 is a member of community no-export. This is correctly advertised to PE-4.
A:PE-4# show router bgp routes vpn-ipv4 10.100.100.0/24 detail 
===============================================================================
 BGP Router ID:192.0.2.4        AS:64496       Local AS:64496      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP VPN-IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
Original Attributes
 
Network        : 10.100.100.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : no-export target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
 
Modified Attributes
 
Network        : 10.100.100.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : no-export target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:PE-4#
The prefix 10.100.101.0/24 is a member of community 64496:101. This is correctly advertised to PE-4.
A:PE-4# show router bgp routes vpn-ipv4 10.100.101.0/24 detail 
===============================================================================
 BGP Router ID:192.0.2.4        AS:64496       Local AS:64496      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
 
===============================================================================
BGP VPN-IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
Original Attributes
 
Network        : 10.100.101.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : 64496:101 target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
 
Modified Attributes
 
Network        : 10.100.101.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : 64496:101 target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:PE-4#
 
The prefix 10.100.103.0/24 is a member of community 64496:103. This is correctly advertised to PE-4.
A:PE-4# show router bgp routes vpn-ipv4 10.100.103.0/24 detail 
===============================================================================
 BGP Router ID:192.0.2.4        AS:64496       Local AS:64496      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP VPN-IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
Original Attributes
 
Network        : 10.100.103.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : 64496:103 target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
 
Modified Attributes
 
Network        : 10.100.103.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : 64496:103 target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:PE-4#
 
The prefix 10.100.104.0/24 is a member of community 64496:104. This is correctly advertised to PE-4.
A:PE-4# show router bgp routes vpn-ipv4 10.100.104.0/24 detail 
===============================================================================
 BGP Router ID:192.0.2.4        AS:64496       Local AS:64496      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP VPN-IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
Original Attributes
 
Network        : 10.100.104.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : 64496:104 target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
 
Modified Attributes
 
Network        : 10.100.104.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : 64496:104 target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:PE-4#
The prefix 10.100.105.0/24 is a member of community 64496:105. This is correctly advertised to PE-4.
A:PE-4# show router bgp routes vpn-ipv4 10.100.105.0/24 detail 
===============================================================================
 BGP Router ID:192.0.2.4        AS:64496       Local AS:64496      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP VPN-IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
Original Attributes
 
Network        : 10.100.105.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : 64496:105 target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
 
Modified Attributes
 
Network        : 10.100.105.0/24
Nexthop        : 192.0.2.1
Route Dist.    : 64496:3                VPN Label      : 262142
Path Id        : None                   
From           : 192.0.2.20
Res. Nexthop   : n/a
Local Pref.    : 100                    Interface Name : int-PE-4-PE-1
Aggregator AS  : None                   Aggregator     : None
Atomic Aggr.   : Not Atomic             MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : 64496:105 target:64496:3
Cluster        : 0.0.0.1
Originator Id  : 192.0.2.1              Peer Router Id : 192.0.2.20
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : Internal               
AS-Path        : No As-Path
Neighbor-AS    : N/A
VPRN Imported  :  3
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:PE-4#
Examine the route table of PE-4 – looking specifically at the BGP-learned routes, the same seven routes are present as valid routes.
A:PE-4# show router 3 route-table protocol bgp-vpn 
===============================================================================
Route Table (Service: 3)
===============================================================================
Dest Prefix[Flags]                            Type    Proto     Age        Pref
      Next Hop[Interface Name]                                    Metric   
-------------------------------------------------------------------------------
10.100.100.0/24                               Remote  BGP VPN   17h24m48s  170
       192.0.2.1 (tunneled)                                         0
10.100.101.0/24                               Remote  BGP VPN   17h24m48s  170
       192.0.2.1 (tunneled)                                         0
10.100.103.0/24                               Remote  BGP VPN   17h24m48s  170
       192.0.2.1 (tunneled)                                         0
10.100.104.0/24                               Remote  BGP VPN   17h24m48s  170
       192.0.2.1 (tunneled)                                         0
10.100.105.0/24                               Remote  BGP VPN   17h24m48s  170
       192.0.2.1 (tunneled)                                         0
172.16.1.0/30                                 Remote  BGP VPN   17h24m48s  170
       192.0.2.1 (tunneled)                                         0
192.0.2.100/32                                Remote  BGP VPN   17h24m48s  170
       192.0.2.1 (tunneled)                                         0
-------------------------------------------------------------------------------
No. of Routes: 7
Flags: n = Number of times nexthop is repeated
       B = BGP backup route available
       L = LFA nexthop available
===============================================================================
A:PE-4# 
Examine the route table of CE-3 – looking specifically at the BGP-learned routes, six routes are present as valid routes, as expected.
A:CE-3# show router route-table protocol bgp 
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags]                            Type    Proto     Age        Pref
      Next Hop[Interface Name]                                    Metric   
-------------------------------------------------------------------------------
10.100.101.0/24                               Remote  BGP       17h32m32s  170
       172.16.0.1                                                   0
10.100.103.0/24                               Remote  BGP       17h32m32s  170
       172.16.0.1                                                   0
10.100.104.0/24                               Remote  BGP       17h32m32s  170
       172.16.0.1                                                   0
10.100.105.0/24                               Remote  BGP       17h32m32s  170
       172.16.0.1                                                   0
172.16.1.0/30                                 Remote  BGP       17h32m32s  170
       172.16.0.1                                                   0
192.0.2.100/32                                Remote  BGP       17h32m32s  170
       172.16.0.1                                                   0
-------------------------------------------------------------------------------
No. of Routes: 6
Flags: n = Number of times nexthop is repeated
       B = BGP backup route available
       L = LFA nexthop available
===============================================================================
A:CE-3#
 
The prefix 10.100.100.0/24 is not received from PE-4 as it is a member of the no-export community.
A:CE-3# show router bgp routes community 64496:100 
===============================================================================
 BGP Router ID:192.0.2.11       AS:64497       Local AS:64497      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
 
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop                                            Path-Id     Label
      As-Path                                                        
-------------------------------------------------------------------------------
No Matching Entries Found
===============================================================================
A:CE-3#
 
Static route 10.100.101.0/24 is received with the correct community 64496:101.
A:CE-3# show router bgp routes community 64496:101 
===============================================================================
 BGP Router ID:192.0.2.11       AS:64497       Local AS:64497      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
 
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop                                            Path-Id     Label
      As-Path                                                        
-------------------------------------------------------------------------------
u*>i  10.100.101.0/24                                    None        None
      172.16.0.1                                         None        -
      64496                                                           
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:CE-3#
 
Static route 10.100.103.0/24 is received with the correct community 64496:103.
A:CE-3# show router bgp routes community 64496:103 
===============================================================================
 BGP Router ID:192.0.2.11       AS:64497       Local AS:64497      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop                                            Path-Id     Label
      As-Path                                                        
-------------------------------------------------------------------------------
u*>i  10.100.103.0/24                                    None        None
      172.16.0.1                                         None        -
      64496                                                           
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:CE-3#
 
Static route 10.100.104.0/24 is received with the correct community 64496:104.
A:CE-3# show router bgp routes community 64496:104 
===============================================================================
 BGP Router ID:192.0.2.11       AS:64497       Local AS:64497      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
 
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop                                            Path-Id     Label
      As-Path                                                        
-------------------------------------------------------------------------------
u*>i  10.100.104.0/24                                    None        None
      172.16.0.1                                         None        -
      64496                                                           
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:CE-3#
Static route 10.100.105.0/24 is received with the correct community 64496:105.
A:CE-3# show router bgp routes community 64496:105 
===============================================================================
 BGP Router ID:192.0.2.11       AS:64497       Local AS:64497      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop                                            Path-Id     Label
      As-Path                                                        
-------------------------------------------------------------------------------
u*>i  10.100.105.0/24                                    None        None
      172.16.0.1                                         None        -
      64496                                                           
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:CE-3# 
 
Aggregate Routes with Communities
An aggregate route can be configured to represent a larger number of prefixes. For example, a set of prefixes 10.101.0.0/24 to 10.101.8.0/24 can be represented as a single aggregate prefix of 10.101.0.0/21.
This is due to the fact that the third octet in the range 0 to 15 can be represented by the 8 bits 00000000 to 00000111. The first 5 bits of this octet are common, along with the previous 2 octets, giving a prefix where the first 21 bits are common. Therefore the aggregate can be written as 10.101.0.0/21.
In order to illustrate the configuration of an aggregate, consider following.
Figure 282: CE-1 Connectivity
Figure 282 shows a CE router (CE-1), in AS 64498, that advertises a series of contiguous prefixes via BGP.
Instead of advertising all of these prefixes out of the VPRN towards an external CE, an aggregate route can be configured that summarizes each set of 8 prefixes and a community can be directly associated with each aggregate route.
The configuration for a VPRN on PE-1, including the external BGP configuration is as follows:
B:PE-1>config>service>vprn# info 
----------------------------------------------
            autonomous-system 64496
            route-distinguisher 64496:4
            auto-bind mpls
            vrf-target target:64496:4
            interface "int-PE-1-CE-1" create
                address 172.16.1.1/30
                sap 1/2/1:2.0 create
                exit
            exit
            bgp
                group "external"
                    family ipv4
                    type external
                    peer-as 64498
                    neighbor 172.16.1.2
                    exit
                exit
                no shutdown
            exit
            no shutdown
 
The neighbor relationship shows:
*A:PE-1# show router 4 bgp neighbor 
===============================================================================
BGP Neighbor
===============================================================================
-------------------------------------------------------------------------------
Peer  : 172.16.1.2
Group : external
-------------------------------------------------------------------------------
Peer AS              : 64498            Peer Port            : 179  
Peer Address         : 172.16.1.2
Local AS             : 64496            Local Port           : 50709
Local Address        : 172.16.1.1
Peer Type            : External         
State                : Established      Last State           : Active
Last Event           : recvKeepAlive
Last Error           : Unrecognized Error
Local Family         : IPv4
Remote Family        : IPv4
Hold Time            : 90               Keep Alive           : 30   
Min Hold Time        : 0                
Active Hold Time     : 90               Active Keep Alive    : 30   
Cluster Id           : None             
Preference           : 170              Num of Update Flaps  : 0    
Recd. Paths          : 1                
IPv4 Recd. Prefixes  : 16               IPv4 Active Prefixes : 16   
IPv4 Suppressed Pfxs : 0                VPN-IPv4 Suppr. Pfxs : 0    
VPN-IPv4 Recd. Pfxs  : 0                VPN-IPv4 Active Pfxs : 0    
Mc IPv4 Recd. Pfxs.  : 0                Mc IPv4 Active Pfxs. : 0    
Mc IPv4 Suppr. Pfxs  : 0                IPv6 Suppressed Pfxs : 0    
IPv6 Recd. Prefixes  : 0                IPv6 Active Prefixes : 0    
VPN-IPv6 Recd. Pfxs  : 0                VPN-IPv6 Active Pfxs : 0    
VPN-IPv6 Suppr. Pfxs : 0                
Mc IPv6 Recd. Pfxs.  : 0                Mc IPv6 Active Pfxs. : 0    
Mc IPv6 Suppr. Pfxs  : 0                L2-VPN Suppr. Pfxs   : 0    
L2-VPN Recd. Pfxs    : 0                L2-VPN Active Pfxs   : 0    
MVPN-IPv4 Suppr. Pfxs: 0                MVPN-IPv4 Recd. Pfxs : 0    
MVPN-IPv4 Active Pfxs: 0                MDT-SAFI Suppr. Pfxs : 0    
MDT-SAFI Recd. Pfxs  : 0                MDT-SAFI Active Pfxs : 0    
Flow-IPv4 Suppr. Pfxs: 0                Flow-IPv4 Recd. Pfxs : 0    
Flow-IPv4 Active Pfxs: 0                Rte-Tgt Suppr. Pfxs  : 0    
Rte-Tgt Recd. Pfxs   : 0                Rte-Tgt Active Pfxs  : 0    
Backup IPv4 Pfxs     : 0                Backup IPv6 Pfxs     : 0    
Mc Vpn Ipv4 Recd. Pf*: 0                Mc Vpn Ipv4 Active P*: 0    
Backup Vpn IPv4 Pfxs : 0                Backup Vpn IPv6 Pfxs : 0    
Input Queue          : 0                Output Queue         : 0    
i/p Messages         : 10               o/p Messages         : 10   
i/p Octets           : 304              o/p Octets           : 308
i/p Updates          : 1                o/p Updates          : 1    
MVPN-IPv6 Suppr. Pfxs: 0                MVPN-IPv6 Recd. Pfxs : 0    
MVPN-IPv6 Active Pfxs: 0                
Flow-IPv6 Suppr. Pfxs: 0                Flow-IPv6 Recd. Pfxs : 0    
Flow-IPv6 Active Pfxs: 0                
Evpn Suppr. Pfxs     : 0                Evpn Recd. Pfxs      : 0    
Evpn Active Pfxs     : 0                
TTL Security         : Disabled         Min TTL Value        : n/a
Graceful Restart     : Disabled         Stale Routes Time    : n/a
Restart Time         : n/a              
Advertise Inactive   : Disabled         Peer Tracking        : Disabled
Advertise Label      : None 
Auth key chain       : n/a
Disable Cap Nego     : Disabled         Bfd Enabled          : Disabled
Flowspec Validate    : Disabled         Default Route Tgt    : Disabled
Aigp Metric          : Disabled         Split Horizon        : Disabled
Damp Peer Oscillatio*: Disabled         Update Errors        : 0    
GR Notification      : Disabled         Fault Tolerance      : Disabled
Rem Idle Hold Time   : 00h00m00s        
Next-Hop Unchanged   : None             
Local Capability     : RtRefresh MPBGP 4byte ASN 
Remote Capability    : RtRefresh MPBGP 4byte ASN 
Local AddPath Capabi*: Disabled
Remote AddPath Capab*: Send - None
                     : Receive - None
Import Policy        : None Specified / Inherited
Export Policy        : None Specified / Inherited
-------------------------------------------------------------------------------
Neighbors : 1
===============================================================================
* indicates that the corresponding row element may have been truncated.
*A:PE-1#
 
The following output shows that 16 BGP routes are received by PE-1.
*A:PE-1# show router 4 bgp routes 
===============================================================================
 BGP Router ID:192.0.2.1        AS:64496       Local AS:64496      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
 
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop                                            Path-Id     Label
      As-Path                                                        
-------------------------------------------------------------------------------
u*>i  10.101.0.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.101.1.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.101.2.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.101.3.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.101.4.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.101.5.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.101.6.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.101.7.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.102.0.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.102.1.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.102.2.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.102.3.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.102.4.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.102.5.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.102.6.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
u*>i  10.102.7.0/24                                      None        None
      172.16.1.2                                         None        -
      64498                                                           
-------------------------------------------------------------------------------
Routes : 16
===============================================================================
*A:PE-1# 
 
 
 
PE-4 also has a VPRN 4 instance configured, so that it will receive the imported BGP routes. The configuration for PE-4 is:
A:PE-4>config>service>vprn# info 
----------------------------------------------
            autonomous-system 64496
            route-distinguisher 64496:4
            auto-bind mpls
            vrf-target target:64496:4
            interface "int-PE-4-CE-3" create
                address 172.16.0.5/30
                sap 1/1/4:4 create
                exit
            exit
            bgp
                group "VPRN-4-ext"
                    peer-as 64497
                    neighbor 172.16.0.6
                    exit
                exit
                no shutdown
            exit
            no shutdown
 
Figure 283 shows the connectivity between PE-4 and CE-3. PE-4 will only forward a summarizing aggregate route towards CE-3.
Figure 283: CE-3 Connectivity
PE-4 receives labelled BGP route prefixes from PE-1 via the route reflector and installs them in the FIB for router instance 4:
*A:PE-4# show router 4 route-table 
===============================================================================
Route Table (Service: 4)
===============================================================================
Dest Prefix[Flags]                            Type    Proto     Age        Pref
      Next Hop[Interface Name]                                    Metric   
-------------------------------------------------------------------------------
10.101.0.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.101.1.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.101.2.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.101.3.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.101.4.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.101.5.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.101.6.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.101.7.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.102.0.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.102.1.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.102.2.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.102.3.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.102.4.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.102.5.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.102.6.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
10.102.7.0/24                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
172.16.0.4/30                                 Local   Local     00h01m00s  0
       int-PE-4-CE-3                                                0
172.16.1.0/30                                 Remote  BGP VPN   00h00m57s  170
       192.0.2.1 (tunneled)                                         0
-------------------------------------------------------------------------------
No. of Routes: 18
Flags: n = Number of times nexthop is repeated
       B = BGP backup route available
       L = LFA nexthop available
===============================================================================
*A:PE-4# 
 
The CE-3 configuration for an interface towards PE-4 is as follows:
*A:CE-3>config>service>ies# info 
            interface "int-CE-3-PE-4-2" create
                address 172.16.0.6/30
                sap 1/1/2:4 create
                exit
            exit
            no shutdown
 
The BGP configuration of CE-3:
*A:CE-3>config>router>bgp# info 
----------------------------------------------
            group "ext"
                peer-as 64496
                neighbor 172.16.0.5
                exit
            exit
 
The BGP neighbor state for PE-4:
*A:PE-4# show router 4 bgp neighbor 172.16.0.6 
===============================================================================
BGP Neighbor
===============================================================================
-------------------------------------------------------------------------------
Peer  : 172.16.0.6
Group : VPRN-4-ext
-------------------------------------------------------------------------------
Peer AS              : 64497            Peer Port            : 179  
Peer Address         : 172.16.0.6
Local AS             : 64496            Local Port           : 50539
Local Address        : 172.16.0.5
Peer Type            : External         
State                : Established      Last State           : Active
Last Event           : recvKeepAlive
Last Error           : Unrecognized Error
Local Family         : IPv4
Remote Family        : IPv4
Hold Time            : 90               Keep Alive           : 30   
Min Hold Time        : 0                
Active Hold Time     : 90               Active Keep Alive    : 30   
Cluster Id           : None             
Preference           : 170              Num of Update Flaps  : 0    
Recd. Paths          : 0                
IPv4 Recd. Prefixes  : 0                IPv4 Active Prefixes : 0    
IPv4 Suppressed Pfxs : 0                VPN-IPv4 Suppr. Pfxs : 0    
VPN-IPv4 Recd. Pfxs  : 0                VPN-IPv4 Active Pfxs : 0    
Mc IPv4 Recd. Pfxs.  : 0                Mc IPv4 Active Pfxs. : 0    
Mc IPv4 Suppr. Pfxs  : 0                IPv6 Suppressed Pfxs : 0    
IPv6 Recd. Prefixes  : 0                IPv6 Active Prefixes : 0    
VPN-IPv6 Recd. Pfxs  : 0                VPN-IPv6 Active Pfxs : 0    
VPN-IPv6 Suppr. Pfxs : 0                
Mc IPv6 Recd. Pfxs.  : 0                Mc IPv6 Active Pfxs. : 0    
Mc IPv6 Suppr. Pfxs  : 0                L2-VPN Suppr. Pfxs   : 0    
L2-VPN Recd. Pfxs    : 0                L2-VPN Active Pfxs   : 0    
MVPN-IPv4 Suppr. Pfxs: 0                MVPN-IPv4 Recd. Pfxs : 0    
MVPN-IPv4 Active Pfxs: 0                MDT-SAFI Suppr. Pfxs : 0    
MDT-SAFI Recd. Pfxs  : 0                MDT-SAFI Active Pfxs : 0    
Flow-IPv4 Suppr. Pfxs: 0                Flow-IPv4 Recd. Pfxs : 0    
Flow-IPv4 Active Pfxs: 0                Rte-Tgt Suppr. Pfxs  : 0    
Rte-Tgt Recd. Pfxs   : 0                Rte-Tgt Active Pfxs  : 0    
Backup IPv4 Pfxs     : 0                Backup IPv6 Pfxs     : 0    
Mc Vpn Ipv4 Recd. Pf*: 0                Mc Vpn Ipv4 Active P*: 0    
Backup Vpn IPv4 Pfxs : 0                Backup Vpn IPv6 Pfxs : 0    
Input Queue          : 0                Output Queue         : 0    
i/p Messages         : 4                o/p Messages         : 4    
i/p Octets           : 102              o/p Octets           : 102
i/p Updates          : 0                o/p Updates          : 0    
MVPN-IPv6 Suppr. Pfxs: 0                MVPN-IPv6 Recd. Pfxs : 0    
MVPN-IPv6 Active Pfxs: 0                
Flow-IPv6 Suppr. Pfxs: 0                Flow-IPv6 Recd. Pfxs : 0    
Flow-IPv6 Active Pfxs: 0                
Evpn Suppr. Pfxs     : 0                Evpn Recd. Pfxs      : 0    
Evpn Active Pfxs     : 0                
TTL Security         : Disabled         Min TTL Value        : n/a
Graceful Restart     : Disabled         Stale Routes Time    : n/a
Restart Time         : n/a              
Advertise Inactive   : Disabled         Peer Tracking        : Disabled
Advertise Label      : None 
Auth key chain       : n/a
Disable Cap Nego     : Disabled         Bfd Enabled          : Disabled
Flowspec Validate    : Disabled         Default Route Tgt    : Disabled
Aigp Metric          : Disabled         Split Horizon        : Disabled
Damp Peer Oscillatio*: Disabled         Update Errors        : 0    
GR Notification      : Disabled         Fault Tolerance      : Disabled
Rem Idle Hold Time   : 00h00m00s        
Next-Hop Unchanged   : None             
Local Capability     : RtRefresh MPBGP 4byte ASN 
Remote Capability    : RtRefresh MPBGP 4byte ASN 
Local AddPath Capabi*: Disabled
Remote AddPath Capab*: Send - None
                     : Receive - None
Import Policy        : None Specified / Inherited
Export Policy        : PE-4-VPN-Agg                                            
-------------------------------------------------------------------------------
Neighbors : 1
===============================================================================
* indicates that the corresponding row element may have been truncated.
*A:PE-4#
 
In order to advertise a summarizing aggregate route with an associated community string, an aggregate route is required. In this case, the 10.101.x.0/24 group of prefixes will be associated with community 64496:101. The 10.102.x.0/24 group of prefixes will be associated with the standard community no-export, so that it will not be advertised to any external peer.
The configuration required is:
*A:PE-4>config>service>vprn# 
            aggregate 10.101.0.0/21 community 64496:101
            aggregate 10.102.0.0/21 community no-export
 
An export policy is required to allow the advertising of the aggregate route. Note that no community is applied using this policy.
*A:PE-4>config>router>policy-options# begin
            policy-statement "PE-4-VPN-Agg"
                entry 10
                    from
                        protocol aggregate
                    exit
                    action accept
                    exit
                exit                  
            exit 
         commit
 
This is applied as an export policy within the group context of the BGP configuration of the VPRN.
*A:PE-4>config>service>vprn#
            bgp
                group "VPRN-4-ext"
                    export "PE-4-VPN-Agg" 
                exit
                no shutdown
            exit
 
The aggregate route 10.101.0.0/21 is received at CE-3 via BGP. The community that was associated with this prefix is seen – 64496:101. Note that the route is seen as an aggregate, with PE-4 as the aggregating router (192.0.2.4). Note also that the “Atomic Aggregate” attribute is present, meaning that PE-4 has not advertised any details of the AS Paths of the composite routes.
A:CE-3# show router bgp routes 10.101.0.0/21 hunt 
===============================================================================
 BGP Router ID:192.0.2.11       AS:64497       Local AS:64497      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
RIB In Entries
-------------------------------------------------------------------------------
Network        : 10.101.0.0/21
Nexthop        : 172.16.0.5
Path Id        : None                   
From           : 172.16.0.5
Res. Nexthop   : 172.16.0.5
Local Pref.    : None                   Interface Name : int-CE-3-PE-4
Aggregator AS  : 64496                  Aggregator     : 192.0.2.4
Atomic Aggr.   : Atomic                 MED            : None
AIGP Metric    : None                   
Connector      : None
Community      : 64496:101
Cluster        : No Cluster Members
Originator Id  : None                   Peer Router Id : 192.0.2.4
Fwd Class      : None                   Priority       : None
Flags          : Used  Valid  Best  IGP  
Route Source   : External               
AS-Path        : 64496 
Neighbor-AS    : 64496
-------------------------------------------------------------------------------
RIB Out Entries
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
A:CE-3# 
 
The aggregate route 10.102.0.0/21 is not received at CE-3, as PE-4 does not advertise it, due to the fact that it is associated with the “no-export” community.
A:CE-3# show router bgp routes 10.102.0.0/21 hunt 
===============================================================================
 BGP Router ID:192.0.2.11       AS:64497       Local AS:64497      
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
 Origin codes  : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
 
===============================================================================
BGP IPv4 Routes
===============================================================================
No Matching Entries Found
===============================================================================
A:CE-3# 
 
Conclusion
Community strings can be added to static and aggregate routes. This example shows the configuration of communities with both static and aggregate routes, together with the associated show outputs which can be used to verify and troubleshoot them.