Inter-AS Model C for VLL

This chapter describes advanced inter-AS model C for Virtual Leased Line (VLL) configurations.

Topics in this chapter include:

Applicability

This chapter was initially written for SR OS Release 8.0.R4. The MD-CLI in the current edition corresponds to SR OS Release 20.10.R2.

Overview

SR OS supports RFC 3107, Carrying Label Information in BGP-4, including VLL/VPLS. BGP SDPs can also be used with PBB-VPLS services.

Internet service providers are looking for mechanisms to implement the VLL and VPLS services across Autonomous Systems (ASs). Service providers may have inter-AS operation as a consequence of delivering inter-provider VLL/VPLS or because they use multiple ASs as a result of acquisitions and mergers.

The objective of this chapter is to describe the interconnection of VLL services across multiple ASs, using inter-AS model C. Inter-AS Model C involves eBGP redistribution of internal system addresses to the neighboring AS using labeled IPv4 routes.

Example topology

Example topology – Inter-AS model C for VLL shows the example topology used for Inter-AS Model C VLL.

Figure 1. Example topology – Inter-AS model C for VLL

The example topology shown in Example topology – Inter-AS model C for VLL consists of three sites in different ASs with each site using SR OS nodes.

AS 64500 contains PE-1 and PE-2, AS 64501 contains PE-3, and AS 64502 contains PE-4 and PE-5. There is a business customer with two remote locations, Site A and Site B, with Customer Edge (CE) devices CE-1 connected to the AS 64500 via PE-1 and CE-5 connected to the AS 64502 via PE-5. A VLL Epipe service is configured between PE-1 and PE-5 to connect site A and site B.

Figure 2. Inter-AS model C for VLL

Configuration

This section describes all of the relevant configuration tasks for the detailed setup shown in Network setup configuration. In this particular example, the following protocols are assumed to be already configured.

  • IS-IS as the IGP with all the nodes being level Level1/Level 2.

  • LDP as the MPLS protocol to signal the transport tunnels within AS 64500 and AS 64502.

    Figure 3. Network setup configuration

BGP configuration

A BGP tunnel must be established between PE-1 and PE-5, therefore, labeled BGP routes must be exchanged for prefixes 192.0.2.1/32 and 192.0.2.5/32 across the ASs. The following shows the BGP configuration — iBGP and eBGP — required for the PE routers to implement an Inter-AS VLL.

The BGP configuration on PE-3 in AS 64501 is as follows:

# on PE-3:
configure {
    router "Base" {
        autonomous-system 64501
        bgp {
            rapid-withdrawal true
            split-horizon true
            group "EBGP" {
                local-as {
                    as-number 64501
                }
            }
            neighbor "192.168.23.1" {
                group "EBGP"
                peer-as 64500
                family {
                    label-ipv4 true
                }
                import {
                    policy ["import-from64500"]
                }
                export {
                    policy ["export-from64502"]
                }
            }
            neighbor "192.168.34.2" {
                group "EBGP"
                peer-as 64502
                family {
                    label-ipv4 true
                }
                import {
                    policy ["import-from64502"]
                }
                export {
                    policy ["export-from64500"]
                }
            }
        }

The address family label-ipv4 must be configured so that MPLS labels are carried along with MP-BGP Network Layer Reachability Information (NLRIs), see chapter "Separate BGP RIBs for Labeled Routes" in the 7450 ESS, 7750 SR, and 7950 XRS Unicast Routing Protocols Advanced Configuration Guide for Classic CLI. The setting split-horizon is optional and prevents that a received route is sent back to the originator, which may result in multiple routes for a certain prefix.

To export the prefixes of the nodes where the Epipe is configured (PE-1 and PE-5) to another AS, a common scenario is to advertise the prefix to be exported within the AS as labeled BGP. Therefore, an export policy is defined for prefix192.0.2.1/32 on PE-1 and this prefix will be advertised with community "64500:0" to the ASBR in AS 64500, in this case to PE-2.

On PE-2, the labeled BGP route for prefix 192.0.2.1/32 is inactive, because the IGP route for that prefix is preferred. The setting advertise-inactive will allow the inactive labeled BGP routes from AS 64500 to be advertised to PE-3 in AS 64501. However, for EBGP sessions on Autonomous System Border Routers (ASBRs) such as PE-2, RFC 8212 is supported, so that routes are neither imported nor exported unless specifically enabled by configuration. Export policy "export-from64500" exports all routes with community "64500:0" and import policy "import-from64502" imports all routes with community "64502:0" which is the community added by the export policy on PE-5.

On PE-5, an export policy is configured to advertise prefix 192.0.2.5/32 with community "64502:0" to ASBR PE-4 in AS 64502.

On PE-4, BGP is configured with advertise-inactive to advertise the labeled BGP route to its EBGP peer, PE-3. Export policy "export-64502:0" exports routes with community "64502:0" to PE-3. Import policy "import-64500:0" imports routes with community "64500:0".

On PE-3, import and export policies are configured toward the EBGP peers. PE-3 imports routes with community "64500:0" from PE-2 and exports these routes to PE-4. Simultaneously, PE-3 imports routes with community "64502:0" from PE-4 and exports these routes to PE-2.

Labeled BGP is used end-to-end between PE-1 and PE-5 and no IGP routes are to be redistributed into BGP, which would be the case if no local BGP labeled routes were advertised within AS 64500 or AS 64502 and only IGP routes were defined within these ASs.

The ASBRs PE-2, PE-3, and PE-4 will swap the BGP labels. PE-3 will advertise the labeled BGP routes learned from AS 64500 to AS 64502 and vice versa and the ASBRs will advertise these labeled routes for remote PE prefixes to their BGP peers. Eventually, PE-1 will have learned a labeled BGP route for prefix 192.0.2.5/32 and PE-5 will have learned a labeled BGP route for prefix 192.0.2.1/32 and a VLL Epipe can be established between PE-1 and PE-5.

The following policies are configured on ASBR PE-2:

# on PE-2:
configure {
    policy-options {
        community "64500:0" {
            member "64500:0" { }
        }
        community "64502:0" {
            member "64502:0" { }
        }
        policy-statement "export-from64500" {
            entry 10 {
                from {
                    community {
                        name "64500:0"
                    }
                }
                action {
                    action-type accept
                }
            }
        }
        policy-statement "import-from64502" {
            entry 10 {
                from {
                    community {
                        name "64502:0"
                    }
                }
                action {
                    action-type accept
                }
            }
        }

The BGP configuration of PE-2 in AS 64500 is as follows:

# on PE-2:
configure {
    router "Base" {
        autonomous-system 64500
        bgp {
            rapid-withdrawal true
            split-horizon true
            group "EBGP" {
                local-as {
                    as-number 64500
                }
            }
            group "IBGP" {
            }
            neighbor "192.0.2.1" {
                group "IBGP"
                next-hop-self true
                peer-as 64500
                family {
                    label-ipv4 true
                }
            }
            neighbor "192.168.23.2" {
                advertise-inactive true
                group "EBGP"
                peer-as 64501
                family {
                    label-ipv4 true
                }
                import {
                    policy ["import-from64502"]
                }
                export {
                    policy ["export-from64500"]
                }
            }
        }

The BGP configuration of ASBR PE-4 in AS 64502 is as follows.The import and export policies are similar to the policies on PE-2.

# on PE-4:
configure {
    router "Base" {
        autonomous-system 64502
        bgp {
            rapid-withdrawal true
            split-horizon true
            group "EBGP" {
                local-as {
                    as-number 64502
                }
            }
            group "IBGP" {
            }
            neighbor "192.0.2.5" {
                group "IBGP"
                next-hop-self true
                peer-as 64502
                family {
                    label-ipv4 true
                }
            }
            neighbor "192.168.34.1" {
                advertise-inactive true
                group "EBGP"
                peer-as 64501
                family {
                    label-ipv4 true
                }
                import {
                    policy ["import-from64500"]
                }
                export {
                    policy ["export-from64502"]
                }
            }
        }

PE-1 and PE-5 are the PEs to which the CEs are connected in AS 64500 and AS 64502. PE-1 and PE-5 advertise their system prefixes as labeled BGP routes to their BGP peers within the AS.

The BGP configuration of PE-1 is as follows:

# on PE-1:
configure {
    router "Base"{
        autonomous-system 64500
        bgp {
            rapid-withdrawal true
            split-horizon true
            group "IBGP" {
                export {
                    policy ["export-PE-1"]
                }
            }
            neighbor "192.0.2.2" {
                group "IBGP"
                next-hop-self true
                peer-as 64500
                family {
                    label-ipv4 true
                }
            }
        }

The BGP configuration of PE-5 in AS 64502 is as follows:

# on PE-5:
configure {
    router "Base" {
        autonomous-system 64502
        bgp {
            rapid-withdrawal true
            split-horizon true
            group "IBGP" {
                export {
                    policy ["export-PEsys"]
                }
            }
            neighbor "192.0.2.4" {
                group "IBGP"
                next-hop-self true
                peer-as 64502
                family {
                    label-ipv4 true
                }
            }
        }

Policy configuration

The export policies on PE-1 and PE-5 advertise the system addresses to the remote AS. The added communities are used by the export and import policies on PE-2, PE-3, and PE-4. The export policy on PE-1 has a prefix list that only contains prefix 192.0.2.1/32 as follows:

# on PE-1:
configure {
    policy-options {
        community "64500:0" {
            member "64500:0" { }
        }
        prefix-list "PE-1" {
            prefix 192.0.2.1/32 type exact {
            }
        }
        policy-statement "export-PE-1" {
            entry 10 {
                from {
                    prefix-list ["PE-1"]
                }
                action {
                    action-type accept
                    origin igp
                    community {
                        add ["64500:0"]
                    }
                }
            }
        }

A similar export policy can be configured for prefix 192.0.2.5/32 on PE-5. However, the export policy on PE-5 is slightly different: the policy has a prefix list that can be applied for prefixes on multiple PEs, but in this case, only prefix 192.0.2.5/32 will be exported:

# on PE-5:
configure {
    policy-options {
        community "64502:0" {
            member "64502:0" { }
        }
        prefix-list "PEsys" {
            prefix 192.0.2.0/29 type longer {
            }
        }
        policy-statement "export-PEsys" {
            entry 10 {
                from {
                    prefix-list ["PEsys"]
                    protocol {
                        name [direct]
                    }
                }
                action {
                    action-type accept
                    origin igp
                    community {
                        add ["64502:0"]
                    }
                }
            }
        }

The same policy could have been applied on PE-1.

Service configuration

Once BGP is configured, the configuration requires the service to be defined (Epipe 1). The focus here is a VLL service, however, it is also possible to have a similar configuration with VPLS services.

The following shows the service level configuration on PE-1:

# on PE-1: 
configure {
     service {
        epipe "Epipe 1" {
            admin-state enable
            description "Tunnel-PE-1-PE-5"
            service-id 1
            customer "1"
            spoke-sdp 15:1 {
            }
            sap 1/1/3:1 {
            }
        }
        sdp 15 {
            admin-state enable
            delivery-type mpls
            bgp-tunnel true
            far-end {
                ip-address 192.0.2.5
            }
        }

The following CLI shows the service level configuration on PE-5:

# on PE-5:
configure {
    service {
        epipe "Epipe 1" {
            admin-state enable
            description "Tunnel-PE-5-PE-1"
            service-id 1
            customer "1"
            spoke-sdp 51:1 {
            }
            sap 1/1/3:1 {
            }
        }
        sdp 51 {
            admin-state enable
            delivery-type mpls
            bgp-tunnel true
            far-end {
                ip-address 192.0.2.1
            }
        }

Show commands and troubleshooting

On PE-5, BGP tunnels exist to the remote AS system addresses that are using LDP as a transport mechanism and the configuration of end-to-end SDPs over which T-LDP service labels are exchanged.

In the following sections, the same commands are launched on the nodes in the following order: first on PE-1 and PE-5; then on PE-3, and finally, on PE-2 and PE-4.

Show commands and troubleshooting on PE-1

The following shows information about SDP 15 on PE-1:

[]
A:admin@PE-1# show service sdp

============================================================================
Services: Service Destination Points
============================================================================
SdpId  AdmMTU  OprMTU  Far End          Adm  Opr         Del     LSP   Sig
----------------------------------------------------------------------------
15     0       1552    192.0.2.5        Up   Up          MPLS    B     TLDP
----------------------------------------------------------------------------
Number of SDPs : 1
----------------------------------------------------------------------------
Legend: R = RSVP, L = LDP, B = BGP, M = MPLS-TP, n/a = Not Applicable
        I = SR-ISIS, O = SR-OSPF, T = SR-TE, F = FPE
============================================================================

On PE-1, the VLL Epipe service is up, as follows:

[]
A:admin@PE-1# show service service-using

===============================================================================
Services
===============================================================================
ServiceId    Type      Adm  Opr  CustomerId Service Name
-------------------------------------------------------------------------------
1            Epipe     Up   Up   1          Epipe 1
2147483648   IES       Up   Down 1          _tmnx_InternalIesService
2147483649   intVpls   Up   Down 1          _tmnx_InternalVplsService
-------------------------------------------------------------------------------
Matching Services : 3
-------------------------------------------------------------------------------
===============================================================================

Two LDP sessions have been established from PE-1: a link LDP session with neighbor PE-2 in AS 64500 and a targeted LDP session with PE-5 in AS 64502, as follows:

[]
A:admin@PE-1# show router ldp session ipv4

==============================================================================
LDP IPv4 Sessions
==============================================================================
Peer LDP Id         Adj Type  State         Msg Sent  Msg Recv  Up Time
------------------------------------------------------------------------------
192.0.2.2:0         Link      Established   109       111       0d 00:04:31
192.0.2.5:0         Targeted  Established   21        23        0d 00:01:20
------------------------------------------------------------------------------
No. of IPv4 Sessions: 2
==============================================================================

The route table on PE-1 shows that the system IP address of PE-5 is reachable using a BGP tunnel:

[]
A:admin@PE-1# show router route-table

===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags]                            Type    Proto     Age        Pref
      Next Hop[Interface Name]                                    Metric
-------------------------------------------------------------------------------
192.0.2.1/32                                  Local   Local     00h06m03s  0
       system                                                       0
192.0.2.2/32                                  Remote  ISIS      00h04m48s  15
       192.168.12.2                                                 10
192.0.2.5/32                                  Remote  BGP_LABEL 00h01m46s  170
       192.0.2.2 (tunneled)                                         10
192.168.12.0/30                               Local   Local     00h06m03s  0
       int-PE-1-PE-2                                                0
-------------------------------------------------------------------------------
No. of Routes: 4
Flags: n = Number of times nexthop is repeated
       B = BGP backup route available
       L = LFA nexthop available
       S = Sticky ECMP requested
===============================================================================

The following tunnel-table on PE-1 shows the details of the LDP, SDP, and BGP tunnels.

[]
A:admin@PE-1# show router tunnel-table

===============================================================================
IPv4 Tunnel Table (Router: Base)
===============================================================================
Destination           Owner     Encap TunnelId  Pref   Nexthop        Metric
   Color
-------------------------------------------------------------------------------
192.0.2.2/32          ldp       MPLS  65537     9      192.168.12.2   10
192.0.2.5/32          sdp       MPLS  15        5      192.0.2.5      0
192.0.2.5/32          bgp       MPLS  262145    12     192.0.2.2      1000
-------------------------------------------------------------------------------
Flags: B = BGP or MPLS backup hop available
       L = Loop-Free Alternate (LFA) hop available
       E = Inactive best-external BGP route
       k = RIB-API or Forwarding Policy backup hop
===============================================================================

The service details for Epipe 1 on PE-1 are as follows:

[]
A:admin@PE-1# show service id 1 base

===============================================================================
Service Basic Information
===============================================================================
Service Id        : 1                   Vpn Id            : 0
Service Type      : Epipe
MACSec enabled    : no
Name              : Epipe 1
Description       : Tunnel-PE-1-PE-5
Customer Id       : 1                   Creation Origin   : manual
Last Status Change: 01/21/2021 16:01:07
Last Mgmt Change  : 01/21/2021 16:00:53
Test Service      : No
Admin State       : Up                  Oper State        : Up
MTU               : 1514
Vc Switching      : False
SAP Count         : 1                   SDP Bind Count    : 1
Per Svc Hashing   : Disabled
Vxlan Src Tep Ip  : N/A
Force QTag Fwd    : Disabled
Oper Group        : <none>

-------------------------------------------------------------------------------
Service Access & Destination Points
-------------------------------------------------------------------------------
Identifier                               Type         AdmMTU  OprMTU  Adm  Opr
-------------------------------------------------------------------------------
sap:1/1/3:1                              q-tag        1518    1518    Up   Up
sdp:15:1 S(192.0.2.5)                    Spok         0       1552    Up   Up
===============================================================================

ICMP is used to verify the IP connectivity from PE-1 to the system IP address of PE-5:

[]
A:admin@PE-1# ping 192.0.2.5 
PING 192.0.2.5 56 data bytes
64 bytes from 192.0.2.5: icmp_seq=1 ttl=64 time=1.91ms.
64 bytes from 192.0.2.5: icmp_seq=2 ttl=64 time=2.06ms.
64 bytes from 192.0.2.5: icmp_seq=3 ttl=64 time=2.02ms.
64 bytes from 192.0.2.5: icmp_seq=4 ttl=64 time=2.01ms.
64 bytes from 192.0.2.5: icmp_seq=5 ttl=64 time=2.02ms.

---- 192.0.2.5 PING Statistics ----
5 packets transmitted, 5 packets received, 0.00% packet loss
round-trip min = 1.91ms, avg = 2.01ms, max = 2.06ms, stddev = 0.050ms
Show commands and troubleshooting on PE-5

The same commands on PE-5 result in the following output:

[]
A:admin@PE-5# show service sdp

============================================================================
Services: Service Destination Points
============================================================================
SdpId  AdmMTU  OprMTU  Far End          Adm  Opr         Del     LSP   Sig
----------------------------------------------------------------------------
51     0       1552    192.0.2.1        Up   Up          MPLS    B     TLDP
----------------------------------------------------------------------------
Number of SDPs : 1
----------------------------------------------------------------------------
Legend: R = RSVP, L = LDP, B = BGP, M = MPLS-TP, n/a = Not Applicable
        I = SR-ISIS, O = SR-OSPF, T = SR-TE, F = FPE
============================================================================
[]
A:admin@PE-5# show service service-using

===============================================================================
Services
===============================================================================
ServiceId    Type      Adm  Opr  CustomerId Service Name
-------------------------------------------------------------------------------
1            Epipe     Up   Up   1          Epipe 1
2147483648   IES       Up   Down 1          _tmnx_InternalIesService
2147483649   intVpls   Up   Down 1          _tmnx_InternalVplsService
-------------------------------------------------------------------------------
Matching Services : 3
-------------------------------------------------------------------------------
===============================================================================
[]
A:admin@PE-5# show router ldp session ipv4

==============================================================================
LDP IPv4 Sessions
==============================================================================
Peer LDP Id         Adj Type  State         Msg Sent  Msg Recv  Up Time
------------------------------------------------------------------------------
192.0.2.1:0         Targeted  Established   52        53        0d 00:04:07
192.0.2.4:0         Link      Established   185       188       0d 00:07:57
------------------------------------------------------------------------------
No. of IPv4 Sessions: 2
==============================================================================
[]
A:admin@PE-5# show router route-table

===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags]                            Type    Proto     Age        Pref
      Next Hop[Interface Name]                                    Metric
-------------------------------------------------------------------------------
192.0.2.1/32                                  Remote  BGP_LABEL 00h05m47s  170
       192.0.2.4 (tunneled)                                         10
192.0.2.4/32                                  Remote  ISIS      00h08m13s  15
       192.168.45.1                                                 10
192.0.2.5/32                                  Local   Local     00h08m19s  0
       system                                                       0
192.168.45.0/30                               Local   Local     00h08m19s  0
       int-PE-5-PE-4                                                0
-------------------------------------------------------------------------------
No. of Routes: 4
Flags: n = Number of times nexthop is repeated
       B = BGP backup route available
       L = LFA nexthop available
       S = Sticky ECMP requested
===============================================================================
[]
A:admin@PE-5# show router tunnel-table

===============================================================================
IPv4 Tunnel Table (Router: Base)
===============================================================================
Destination           Owner     Encap TunnelId  Pref   Nexthop        Metric
   Color
-------------------------------------------------------------------------------
192.0.2.1/32          sdp       MPLS  51        5      192.0.2.1      0
192.0.2.1/32          bgp       MPLS  262145    12     192.0.2.4      1000
192.0.2.4/32          ldp       MPLS  65537     9      192.168.45.1   10
-------------------------------------------------------------------------------
Flags: B = BGP or MPLS backup hop available
       L = Loop-Free Alternate (LFA) hop available
       E = Inactive best-external BGP route
       k = RIB-API or Forwarding Policy backup hop
===============================================================================
[]
A:admin@PE-5# show service id 1 base

===============================================================================
Service Basic Information
===============================================================================
Service Id        : 1                   Vpn Id            : 0
Service Type      : Epipe
MACSec enabled    : no
Name              : Epipe 1
Description       : Tunnel-PE-5-PE-1
Customer Id       : 1                   Creation Origin   : manual
Last Status Change: 01/21/2021 16:01:07
Last Mgmt Change  : 01/21/2021 16:00:49
Test Service      : No
Admin State       : Up                  Oper State        : Up
MTU               : 1514
Vc Switching      : False
SAP Count         : 1                   SDP Bind Count    : 1
Per Svc Hashing   : Disabled
Vxlan Src Tep Ip  : N/A
Force QTag Fwd    : Disabled
Oper Group        : <none>

-------------------------------------------------------------------------------
Service Access & Destination Points
-------------------------------------------------------------------------------
Identifier                               Type         AdmMTU  OprMTU  Adm  Opr
-------------------------------------------------------------------------------
sap:1/1/3:1                              q-tag        1518    1518    Up   Up
sdp:51:1 S(192.0.2.1)                    Spok         0       1552    Up   Up
===============================================================================
[]
A:admin@PE-5# ping 192.0.2.1 
PING 192.0.2.1 56 data bytes
64 bytes from 192.0.2.1: icmp_seq=1 ttl=64 time=1.83ms.
64 bytes from 192.0.2.1: icmp_seq=2 ttl=64 time=2.06ms.
64 bytes from 192.0.2.1: icmp_seq=3 ttl=64 time=2.01ms.
64 bytes from 192.0.2.1: icmp_seq=4 ttl=64 time=2.08ms.
64 bytes from 192.0.2.1: icmp_seq=5 ttl=64 time=2.15ms.

---- 192.0.2.1 PING Statistics ----
5 packets transmitted, 5 packets received, 0.00% packet loss
round-trip min = 1.83ms, avg = 2.03ms, max = 2.15ms, stddev = 0.107ms

On PE-5, the BGP route to the system IP address of PE-1 can been seen with PE-4 as the next hop:

[]
A:admin@PE-5# show router bgp routes label-ipv4
===============================================================================
 BGP Router ID:192.0.2.5        AS:64502       Local AS:64502
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
                 l - leaked, x - stale, > - best, b - backup, p - purge
 Origin codes  : i - IGP, e - EGP, ? - incomplete

===============================================================================
BGP Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop (Router)                                   Path-Id     IGP Cost
      As-Path                                                        Label
-------------------------------------------------------------------------------
u*>i  192.0.2.1/32                                       100         None
      192.0.2.4                                          None        10
      64501 64500                                                    524285
-------------------------------------------------------------------------------
Routes : 1
===============================================================================

On PE-5, the FIB on slot 1 shows that the system IP address of PE-1 is reachable using BGP over an LDP transport to PE-4:

[]
A:admin@PE-5# show router fib 1

===============================================================================
FIB Display
===============================================================================
Prefix [Flags]                                              Protocol
  NextHop
-------------------------------------------------------------------------------
192.0.2.1/32                                                BGP_LABEL
  192.0.2.4 (Transport:LDP)
192.0.2.4/32                                                ISIS
  192.168.45.1 (int-PE-5-PE-4)
192.0.2.5/32                                                LOCAL
  192.0.2.5 (system)
192.168.45.0/30                                             LOCAL
  192.168.45.0 (int-PE-5-PE-4)
-------------------------------------------------------------------------------
Total Entries : 4
-------------------------------------------------------------------------------
===============================================================================
Show commands on PE-3

The show commands on router PE-3 in AS 64501 are as follows:

[]
A:admin@PE-3# show router bgp summary all

===============================================================================
BGP Summary
===============================================================================
Legend : D - Dynamic Neighbor
===============================================================================
Neighbor
Description
ServiceId          AS PktRcvd InQ  Up/Down   State|Rcv/Act/Sent (Addr Family)
                      PktSent OutQ
-------------------------------------------------------------------------------
192.168.23.1
Def. Instance  64500       22    0 00h09m12s 1/1/1 (Lbl-IPv4)
                           22    0
192.168.34.2
Def. Instance  64502       23    0 00h09m04s 1/1/1 (Lbl-IPv4)
                           25    0

-------------------------------------------------------------------------------
[]
A:admin@PE-3# show router bgp routes label-ipv4
===============================================================================
 BGP Router ID:192.0.2.3        AS:64501       Local AS:64501
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
                 l - leaked, x - stale, > - best, b - backup, p - purge
 Origin codes  : i - IGP, e - EGP, ? - incomplete

===============================================================================
BGP Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop (Router)                                   Path-Id     IGP Cost
      As-Path                                                        Label
-------------------------------------------------------------------------------
u*>i  192.0.2.1/32                                       None        None
      192.168.23.1                                       None        0
      64500                                                          524285
u*>i  192.0.2.5/32                                       None        None
      192.168.34.2                                       None        0
      64502                                                          524284
-------------------------------------------------------------------------------
Routes : 2
===============================================================================

The BGP labels are swapped at PE-3, as follows:

[]
A:admin@PE-3# show router bgp inter-as-label

===============================================================================
BGP Inter-AS labels
Flags: B - entry has backup, P - entry is promoted
===============================================================================
NextHop                       Received       Advertised     Label
                              Label          Label          Origin
-------------------------------------------------------------------------------
192.168.23.1                  524285         524287         External
192.168.34.2                  524284         524286         External
-------------------------------------------------------------------------------
Total Labels allocated:   2
===============================================================================

The routing table on PE-3 includes BGP labeled routes to PE-1 and PE-5, as follows:

[]
A:admin@PE-3# show router route-table

===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags]                            Type    Proto     Age        Pref
      Next Hop[Interface Name]                                    Metric
-------------------------------------------------------------------------------
192.0.2.1/32                                  Remote  BGP_LABEL 00h10m02s  170
       192.168.23.1                                                 0
192.0.2.3/32                                  Local   Local     00h12m42s  0
       system                                                       0
192.0.2.5/32                                  Remote  BGP_LABEL 00h09m23s  170
       192.168.34.2                                                 0
192.168.23.0/30                               Local   Local     00h12m42s  0
       int-PE-3-PE-2                                                0
192.168.34.0/30                               Local   Local     00h12m42s  0
       int-PE-3-PE-4                                                0
-------------------------------------------------------------------------------
No. of Routes: 5
Flags: n = Number of times nexthop is repeated
       B = BGP backup route available
       L = LFA nexthop available
       S = Sticky ECMP requested
===============================================================================
Show commands on PE-2

The commands on PE-2 are as follows:

[]
A:admin@PE-2# show router bgp summary all 

===============================================================================
BGP Summary
===============================================================================
Legend : D - Dynamic Neighbor
===============================================================================
Neighbor
Description
ServiceId          AS PktRcvd InQ  Up/Down   State|Rcv/Act/Sent (Addr Family)
                      PktSent OutQ
-------------------------------------------------------------------------------
192.0.2.1
Def. Instance  64500       36    0 00h16m24s 1/0/1 (Lbl-IPv4)
                           36    0           
192.168.23.2
Def. Instance  64501       36    0 00h16m19s 1/1/1 (Lbl-IPv4)
                           36    0           

-------------------------------------------------------------------------------

The BGP labels are swapped by PE-2 as follows:

[]
A:admin@PE-2# show router bgp inter-as-label

===============================================================================
BGP Inter-AS labels
Flags: B - entry has backup, P - entry is promoted
===============================================================================
NextHop                       Received       Advertised     Label
                              Label          Label          Origin
-------------------------------------------------------------------------------
192.0.2.1                     524285         524285         Internal
192.168.23.2                  524286         524284         External
-------------------------------------------------------------------------------
Total Labels allocated:   2
===============================================================================
[]
A:admin@PE-2# show router route-table

===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags]                            Type    Proto     Age        Pref
      Next Hop[Interface Name]                                    Metric
-------------------------------------------------------------------------------
192.0.2.1/32                                  Remote  ISIS      00h13m43s  15
       192.168.12.1                                                 10
192.0.2.2/32                                  Local   Local     00h13m50s  0
       system                                                       0
192.0.2.5/32                                  Remote  BGP_LABEL 00h11m01s  170
       192.168.23.2                                                 0
192.168.12.0/30                               Local   Local     00h13m50s  0
       int-PE-2-PE-1                                                0
192.168.23.0/30                               Local   Local     00h13m50s  0
       int-PE-2-PE-3                                                0
-------------------------------------------------------------------------------
No. of Routes: 5
Flags: n = Number of times nexthop is repeated
       B = BGP backup route available
       L = LFA nexthop available
       S = Sticky ECMP requested
===============================================================================
Show commands on PE-4

The show commands on PE-4 are the following:

[]
A:admin@PE-4# show router bgp summary all

===============================================================================
BGP Summary
===============================================================================
Legend : D - Dynamic Neighbor
===============================================================================
Neighbor
Description
ServiceId          AS PktRcvd InQ  Up/Down   State|Rcv/Act/Sent (Addr Family)
                      PktSent OutQ
-------------------------------------------------------------------------------
192.0.2.5
Def. Instance  64502       29    0 00h12m43s 1/0/1 (Lbl-IPv4)
                           29    0
192.168.34.1
Def. Instance  64501       29    0 00h12m53s 1/1/1 (Lbl-IPv4)
                           30    0

-------------------------------------------------------------------------------
[]
A:admin@PE-4# show router bgp routes label-ipv4
===============================================================================
 BGP Router ID:192.0.2.4        AS:64502       Local AS:64502
===============================================================================
 Legend -
 Status codes  : u - used, s - suppressed, h - history, d - decayed, * - valid
                 l - leaked, x - stale, > - best, b - backup, p - purge
 Origin codes  : i - IGP, e - EGP, ? - incomplete

===============================================================================
BGP Routes
===============================================================================
Flag  Network                                            LocalPref   MED
      Nexthop (Router)                                   Path-Id     IGP Cost
      As-Path                                                        Label
-------------------------------------------------------------------------------
u*>i  192.0.2.1/32                                       None        None
      192.168.34.1                                       None        0
      64501 64500                                                    524287
*i    192.0.2.5/32                                       100         None
      192.0.2.5                                          None        10
      No As-Path                                                     524285
-------------------------------------------------------------------------------
Routes : 2
===============================================================================
[]
A:admin@PE-4# show router bgp inter-as-label

===============================================================================
BGP Inter-AS labels
Flags: B - entry has backup, P - entry is promoted
===============================================================================
NextHop                       Received       Advertised     Label
                              Label          Label          Origin
-------------------------------------------------------------------------------
192.0.2.5                     524285         524284         Internal
192.168.34.1                  524287         524285         External
-------------------------------------------------------------------------------
Total Labels allocated:   2
===============================================================================

Conclusion

The BGP tunnel-based SDP binding is allowed for VLL and VPLS services, including PBB-VPLS. Using RFC 3107, it is possible to implement inter-AS Model C VLLs.

The example used in this chapter illustrates the configuration of an Inter-AS VLL providing access to CE sites. Troubleshooting commands also have been shown to verify all the procedures.