EVPN for Layer 2 ELAN services

EVPN Layer 2 without multihoming includes the implementation of the BGP-EVPN address family and support for the following route types:

• EVPN MAC/IP route (or type 2, RT2)

• EVPN Inclusive Multicast Ethernet Tag route (IMET or type 3, RT3)

The MAC/IP route is used to convey the MAC and IP information of hosts connected to subinterfaces in the MAC-VRF. The IMET route is advertised as soon as BGP-EVPN is enabled in the MAC-VRF; it has the following purpose:

• auto-discovery of the remote VXLAN VTEPs or MPLS TEPs (termination endpoints) attached to the same EVI

  or BD

• creation of a VXLAN or MPLS default flooding list in the MAC-VRF so that BUM frames are replicated

Advertisement of the MAC/IP and IMET routes is configured on a per-MAC-VRF basis. The following example shows the default setting advertise true, which advertises MAC/IP and IMET routes. The example is for EVPN-VXLAN services, but is also valid for EVPN-MPLS.

--{ candidate shared default }--[ network-instance blue protocols bgp-evpn bgp-
instance 1 ]--
# info detail
    admin-state enable
    vxlan-interface vxlan1.1
    evi 1
    ecmp 1
    default-admin-tag 0
    routes {
        next-hop use-system-ipv4-address
        mac-ip {
            advertise true
        }
        inclusive-mcast {
            advertise true
        }
    }

Upon receiving EVPN routes in the context of a MAC-VRF, the router creates EVPN destinations, referred to as EVPN-VXLAN destinations or EVPN-MPLS destinations, depending on whether the BGP-EVPN instance is configured for VXLAN or MPLS encapsulation.

--{ [FACTORY] + candidate shared default }--[ ]--
# info from state tunnel-interface vxlan1 vxlan-interface 1 bridge-table unicast- destinations destination * vni * 
    tunnel-interface vxlan1 { 
        vxlan-interface 1 { 
            bridge-table { 
                unicast-destinations { 
                    destination 10.44.44.4 vni 1 { 
                        destination-index 677716962904 // destination index 
                        statistics { 
                        } 
                        mac-table { 
                            mac 00:00:00:01:01:04 {
                                type evpn-static 
                                last-update "16 hours ago" 
                            }
                        }
                    }
                }
            }
        } 
    }
--{ [FACTORY] + candidate shared default }--[ ]--
# info from state network-instance blue bridge-table mac-table mac 00:00:00:01:01:04
    network-instance blue {
        bridge-table {
            mac-table {
                mac 00:00:00:01:01:04 {
                    destination-type vxlan
                    destination-index 677716962904 // destination index
                    type evpn-static
                    last-update "16 hours ago"
                    destination "vxlan-interface:vxlan1.1 vtep:10.44.44.4 vni:1"
                }
            }
        }
    }

--{ [FACTORY] + candidate shared default }--[ ]-- 
# info from state tunnel-interface vxlan1 vxlan-interface 1 bridge-table multicast-destinations 
    tunnel-interface vxlan1 { 
        vxlan-interface 1 { 
            bridge-table { 
                multicast-destinations { 
                    destination 40.1.1.2 vni 1 { 
                        multicast-forwarding BUM
                        destination-index 46428593833 
                    } 
                    destination 40.1.1.3 vni 1 { 
                        multicast-forwarding BUM 
                        destination-index 46428593835 
                    } 
                    destination 40.1.1.4 vni 1 { 
                        multicast-forwarding BUM 
                        destination-index 46428593829 
                    }
                } 
            } 
        } 
    } 

--{ + candidate shared default }--[ network-instance MAC-VRF-2 protocols bgp-evpn bgp-instance 1 mpls ]--
# info from state
control-word false
bridge-table {
  ingress-multicast-mpls-label 1001
  ingress-unicast-mpls-label 1000
  unicast-destinations {
    destination 100.0.0.4 evi-label 1000 tunnel-id 303822694264 {
      destination-index 303822694290
      statistics {
        active-entries 1
        total-entries 1
        failed-entries 0
        mac-type evpn {
          active-entries 0
          total-entries 0
          failed-entries 0
        }
        mac-type evpn-static {
          active-entries 1
          total-entries 1
          failed-entries 0
        }
      }
      mac-table {
        mac 1A:01:0B:FF:00:24 {
          type evpn-static
          last-update "2024-06-27T07:55:05.000Z (9 hours ago)"
        }
      }
    }
  }
  statistics {
    active-entries 1
    total-entries 1
    failed-entries 0
    mac-type evpn {
      active-entries 0
      total-entries 0
      failed-entries 0
    }
    mac-type evpn-static {
      active-entries 1
      total-entries 1
      failed-entries 0
    }
  }
  multicast-destinations {
    multicast-limit {
      maximum-entries 1024
      current-usage 1
    }
    destination 100.0.0.4 evi-label 5000 tunnel-id 303822694264 {
      multicast-forwarding BUM
      destination-index 303822694291
    }
  }
}
next-hop-resolution {
  allowed-tunnel-types [
    ldp
    sr-isis
  ]
}

When a MAC is received from multiple sources, the route is selected based on the priority listed in MAC selection. Learned and EVPN-learned routes have equal priority; the latest received route is selected.

When multiple EVPN-learned MAC/IP routes arrive for the same MAC but with a different key (for example, two routes for MAC M1 with different route-distinguishers), a selection is made based on the following priority:

1. EVPN MACs with higher SEQ number

2. EVPN MACs with lower IP next-hop

3. EVPN MACs with lower Ethernet Tag

4. EVPN MACs with lower RD

You can configure the BGP next hop to be used for the EVPN routes advertised for a network instance. This next hop is by default the IPv4 address configured in interface system 0.0 of the default network instance. However, the next-hop address can be changed to any IPv4 address.

The system does not check that the configured IP address exists in the default network instance. Any valid IP address can be used as next hop of the EVPN routes advertised for the network instance, irrespective of its existence in any subinterface of the system. However, the receiver leaf nodes create their unicast, multicast and ES destinations to this advertised next-hop, so it is important that the configured next-hop is a valid IPv4 address.

When the system or loopback interface configured for the BGP next-hop is administratively disabled, EVPN still advertises the routes, as long as a valid IP address is available for the next-hop. However, in EVPN-VXLAN instances received VXLAN traffic on that interface is dropped.

The following example configures a BGP next hop to be used for the EVPN routes advertised for a network instance.

--{ candidate shared default }--[ network-instance MAC-VRF-1 protocols bgp-evpn bgp-instance 1 ]--
# info
    routes {
        bridge-table {
          next-hop 1.1.1.1
        }
    }

EVPN relies on three different procedures to handle multihoming: DF election, split-horizon, and aliasing. DF election is relevant to single-active and all-active multihoming; split-horizon and aliasing are relevant only to all-active multihoming.

• Designated Forwarder (DF) Election

  The DF is the leaf that forwards BUM traffic in the ES. Only one DF can exist per ES at a time, and it is elected based on the exchange of ES routes (type 4) and the subsequent DF Election Algorithm (DF Election Alg).

  In single-active multihoming, the non-DF leafs bring down the subinterface associated with the ES.

  In all-active multihoming, the non-DF leafs do not forward BUM traffic received from remote EVPN PEs.

• split-horizon

  This is the mechanism by which BUM traffic received from a peer ES PE is filtered so that it is not looped back to the CE that first transmitted the frame. This mechanism is different depending on whether the transport is VXLAN or MPLS. For VXLAN, local bias is applied, as described in RFC 8365. For EVPN-MPLS packets, the split-horizon filtering is based on ESI-label based filtering, as described in RFC 7432.

• aliasing

  This is the procedure by which PEs that are not attached to the ES can process non-zero ESI MAC/IP routes and AD routes and create ES destinations to which per-flow ECMP can be applied.

To support multihoming, EVPN supports two additional route types:

• ES routes (type 4)

  Used for ES discovery on all the leafs attached to the ES and DF Election.

  ES routes use an ES-import route target extended community, its value derived from the ESI, so that its distribution is limited to only the leafs that are attached to the ES.

  The ES route is advertised with the DF Election extended community, which indicates the intent to use a specific DF Election Alg and capabilities.

  On reception of the remote ES routes, each PE builds a DF candidate list based on the originator IP of the ES routes. Then, based on the agreed DF Election Alg, each PE elects one of the candidates as DF for each MAC-VRF where the ES is defined.

• AD route (type 1)

  Advertised to the leafs attached to an ES. There are two versions of AD routes:

  • AD per-ES route

    Used to advertise the multihoming mode (single-active or all-active) and the ESI label, which is not advertised or processed in case of EVPN-VXLAN, but it is advertised and used in the case of EVPN-MPLS. Its withdrawal enables the mass withdrawal procedures in the remote PEs.

  • AD per-EVI route

    Used to advertise the availability of an ES in an EVI and its VNI/label. It is needed by the remote leafs for the aliasing procedures.

  Both versions of AD routes can influence the DF Election. Their withdrawal from a leaf results in removing that leaf from consideration for DF Election for the associated EVI, as long as ac-df exclude is configured. The AC-DF capability can be set to exclude only if the DF election algorithm type is set to preference.

EVPN Layer 2 single-homing configuration shows a single-active ES attached to two leaf nodes. In this configuration, the ES in single-active mode can be configured to do the following:

• associate with an Ethernet interface or a LAG interface, as all-active ESes

• coexist with all-active ESes on the same node, as well as in the same MAC-VRF service

• signal the non-DF state to the CE by using LACP out-of-sync signaling or power off

  Optionally, the ES can be configured not to signal to the CE. When the LACP sync flag or power off is used to signal the non-DF state to the CE or server, all of the subinterfaces are active on the same node; that is, load balancing is not per-service, but rather per-port. This mode of operation is known as EVPN multihoming port-active mode.

• connect to a CE that uses a single LAG to connect to the ES or separate LAG/ports per leaf in the ES

All peers in the ES must be configured with the same multihoming mode; if the nodes are not configured consistently, the oper-multi-homing-mode in state is single-active. From a hardware resource perspective, no local-bias-table entries are populated for ESes in single-active mode.

The following features work in conjunction with single-active mode:

• Preference-based DF election/non-revertive option configures ES peers to elect a DF based on a preference value, as well as an option to prevent traffic from reverting back to a former DF node.

• Attachment Circuit-influenced DF Election (AC-DF) allows the DF election candidate list for a network instance to be modified based on the presence of the AD per-EVI and per-ES routes.

• Standby LACP-based or power-off signaling configures how the node’s non-DF state is signaled to the multihomed CE.

After the system boots, the reload-delay timer keeps an interface shut down with the laser off for a configured amount of time until connectivity with the rest of network is established. When applied to an access multihomed interface, typically an ES interface), this delay can prevent black-holing traffic coming from the multihomed server or CE.

In EVPN multihoming scenarios, if one leaf in the ES peer group is rebooting, coming up after an upgrade or a failure, it is important for the ES interface not to become active until after the node is ready to forward traffic to the core. If the ES interface comes up too quickly and the node has not programmed its forwarding tables yet, traffic from the server is black-holed. To prevent this from happening, you can configure a reload-delay timer on the ES interface so that the interface does not become active until after network connectivity is established.

When a reload-delay timer is configured, the interface port is shut down and the laser is turned off from the time that the system determines the interface state following a reboot or reload of the XDP process until the number of seconds specified in the reload-delay timer elapse.

The reload-delay timer is only supported on Ethernet interfaces that are not enabled with breakout mode. For a multihomed LAG interface, configure the reload-delay timer on all the interface members. The reload-delay timer can be from 1 to 86 400 seconds. There is no default value; if not configured for an interface, there is no reload-delay timer.

Only configure ES interfaces with a non-zero reload-delay timer. Do not configure a reload-delay timer on single-homed interfaces and network interfaces (used to forward EVPN traffic).

The following example sets the reload-delay timer for an interface to 20 seconds. The timer starts following a system reboot or when the IMM is reconnected, and the system determines the interface state. During the timer period, the interface is deactivated and the port laser is inactive.

--{ * candidate shared default }--[  ]--
# info interface ethernet-1/1
    interface ethernet-1/1 {
        admin-state enable
        ethernet {
            reload-delay 20
        }
    }

When the reload-delay timer is running, the port-oper-down-reason for the port is shown as interface-reload-timer-active. The reload-delay-expires state indicates the amount of time remaining until the port becomes active. For example:

--{ * candidate shared default }--[  ]--
# info from state interface ethernet-1/1
    interface ethernet-1/1 {
        description eth_seg_1
        admin-state enable
        mtu 9232
        loopback-mode false
        ifindex 671742
        oper-state down
        oper-down-reason interface-reload-time-active
        last-change "51 seconds ago"
        linecard 1
        forwarding-complex 0
        vlan-tagging true
        ...
        ethernet {
            auto-negotiate false
            lacp-port-priority 32768
            port-speed 100G
            hw-mac-address 00:01:01:FF:00:15
            reload-delay 20
            reload-delay-expires "18 seconds from now"
            flow-control {
                receive false
                transmit false
            }
        }
    }

The following is an example of a single-active multihoming configuration, including standby signaling power-off, AC-DF capability, and preference-based DF algorithm.

The following configures power-off signaling and the reload delay timer for an interface:

--{ * candidate shared default }--[  ]--
# info interface ethernet-1/21 ethernet
    standby-signaling power-off // needed to signal non-DF state to the CE
    reload-delay 100 // upon reboot, this is required to avoid attracting traffic 
from the multi-homed CE until the node is ready to forward.
// The time accounts for the time it takes all network protocols to be up 
and forwarding entries ready.

The following configures DF election settings for the ES, including preference-based DF election and a preference value for the DF election alg. The ac-df setting is set to exclude, which disables the AC-DF capability. The non-revertive option is enabled, which prevents traffic from reverting back to a former DF node when the node reconnects to the network.

--{ * candidate shared default }--[ system network-instance protocols evpn ethernet-
segments bgp-instance 1 ethernet-segment eth_seg_1 ]--
# info
    admin-state enable
    esi 00:01:00:00:00:00:00:00:00:00
    interface ethernet-1/21
    multi-homing-mode single-active
    df-election {
        interface-standby-signaling-on-non-df { // presence container that enables 
the standby-signaling for the ES
        }
        algorithm {
            type preference // enables the use of preference based DF election
            preference-alg {
                preference-value 100 // changes the default 32767 to a 
specific value
                capabilities {
                    ac-df exclude // turns off the default ac-df capability
                    non-revertive true // enables the non-revertive mode
                }
            }
        }
    }

The following shows the state, and consequently the configuration, of an ES for single-active multihoming and indicates the default settings for the algorithm or operational type. Nokia recommends configuring all of the peers in the ES with the same algorithm type. However, if that is not the case, all the peers fall back to the default algorithm.

--{ * candidate shared default }--[ system network-instance protocols evpn ethernet-
segments bgp-instance 1 ethernet-segment eth_seg_1 ]--
# info
    admin-state enable
    oper-state up
    esi 00:01:00:00:00:00:00:00:00:00
    interface ethernet-1/21
    multi-homing-mode single-active
    oper-multi-homing-mode single-active // oper mode may be different if not all 
the ES peers are configured in the same way
    df-election {
        interface-standby-signaling-on-non-df {
        }
        algorithm {
            type preference
            oper-type preference // if at least one peer in the ES is in type 
default, all the peers will fall back to default
            preference-alg {
                preference-value 100
                capabilities {
                    ac-df exclude
                    non-revertive true
                }
            }
        }
    }
    routes {
        next-hop use-system-ipv4-address
        ethernet-segment {
            originating-ip use-system-ipv4-address
        }
    }
    association {
        network-instance blue {
            bgp-instance 1 {
                designated-forwarder-role-last-change "2 seconds ago"
                designated-forwarder-activation-start-time "2 seconds ago"
                designated-forwarder-activation-time 3
                computed-designated-forwarder-candidates {
                    designated-forwarder-candidate 40.1.1.1 {
                        add-time "2 seconds ago"
                        designated-forwarder true
                    }
                    designated-forwarder-candidate 40.1.1.2 {
                        add-time "2 minutes ago"
                        designated-forwarder false
                    }
                }
            }
        }
    }
}

To display information about the ES, use the show system network-instance ethernet-segments command. For example:

--{ [FACTORY] + candidate shared default }--[  ]--
# show system network-instance ethernet-segments eth_seg_1
------------------------------------------------------------------------------------
eth_seg_1 is up, single-active
  ESI      : 00:01:00:00:00:00:00:00:00:00
  Alg      : preference
  Peers    : 40.1.1.2
  Interface: ethernet-1/21
  Network-instances:
     blue
      Candidates : 40.1.1.1 (DF), 40.1.1.2
      Interface : ethernet-1/21.1
------------------------------------------------------------------------------------
Summary
 1 Ethernet Segments Up
 0 Ethernet Segments Down
------------------------------------------------------------------------------------

The detail option displays more information about the ES. For example:

--{ [FACTORY] + candidate shared default }--[  ]--
# show system network-instance ethernet-segments eth_seg_1 detail
====================================================================================
Ethernet Segment
====================================================================================
Name                 : eth_seg_1
40.1.1.1 (DF)
Admin State          : enable              Oper State        : up
ESI                  : 00:01:00:00:00:00:00:00:00:00
Multi-homing         : single-active          Oper Multi-homing : single-active
Interface            : ethernet-1/21
ES Activation Timer  : None
DF Election          : preference          Oper DF Election  : preference
 
Last Change          : 2021-04-06T08:49:44.017Z
====================================================================================
 MAC-VRF    Actv Timer Rem   DF
eth_seg_1   0                Yes
------------------------------------------------------------------------------------
DF Candidates
------------------------------------------------------------------------------------
Network-instance       ES Peers
blue                   40.1.1.1 (DF)
blue                   40.1.1.2
====================================================================================

On the DF node, the info from state command displays the following:

--{ [FACTORY] + candidate shared default }--[  ]--
# info from state interface ethernet-1/21 | grep oper
        oper-state up
            oper-state not-present
            oper-state up

--{ [FACTORY] + candidate shared default }--[  ]--
# info from state network-instance blue interface ethernet-1/21.1
    network-instance blue {
        interface ethernet-1/21.1 {
            oper-state up
            oper-mac-learning up
            index 6
            multicast-forwarding BUM
        }
    }

On the non-DF node, the info from state command displays the following:

--{ [FACTORY] + candidate shared default }--[  ]--
# info from state interface ethernet-1/21 | grep oper
        oper-state down
        oper-down-reason standby-signaling
            oper-state not-present
            oper-state down
            oper-down-reason port-down

--{ [FACTORY] + candidate shared default }--[  ]--
# info from state network-instance blue interface ethernet-1/21.1
    network-instance blue {
        interface ethernet-1/21.1 {
            oper-state down
            oper-down-reason subif-down
            oper-mac-learning up
            index 7
            multicast-forwarding none
        }
    }

When the ES is used for EVPN-MPLS segments, the state also shows the allocated ESI label; for example:

--{ + candidate shared default }--[ system network-instance protocols evpn ethernet-segments bgp-instance 1 ]--
# info from state ethernet-segment ES-ce31 esi-label
  esi-label 500

When dynamic learning for proxy-ARP/ND is enabled, all frames coming into bridged subinterfaces of the MAC-VRF that have Ethertype 0x0806 (for proxy-ARP) or ICMPv6 ND (for proxy-ND) are sent to the CPM for learning. This includes ARP-request and ARP-reply (including gratuitous ARP) messages and neighbor solicitation (NS) and neighbor advertisement (NA) messages (for ND). Dynamic entries in the proxy-ARP/ND table are created from both message types. For proxy-ND, dynamic entries are created only from NA messages. Learning an entry is done irrespective of the MAC DA of the ARP or ND packet (unicast or broadcast).

The dynamically learned information in the table is based on the ARP/ND payload MAC SA and IP DA, and not the frame outer MAC SA, although they normally match. A valid MAC SA must be present for the entry to be learned.

In addition to learning the dynamic entry from the ARP-request, ARP-reply, or NA, the system re-injects and forwards messages as follows:

• For received ARP-request or NS messages, the system looks up the requested IP address, and if the lookup is successful, it sends an ARP-reply or NA with the MAC→IP information. If the lookup is not successful, the ARP-request/NS is re-injected and flooded based on the flood list and the configured flooding option, with source squelching. See Configuring proxy-ARP/ND traffic flooding options.

  The re-injected ARP-request or NS keeps all existing non-service-delimiting tags of the original frame. Unicast ARP-requests are replied to if there is an entry in the proxy table. If the lookup is not successful, the frame is forwarded to the MAC DA.

• For ARP-reply/NA messages, the MAC DA (unicast) is looked up in the MAC table. In case of a hit, the frame is re-injected and unicasted based on the MAC table information. If there is no hit, the frame is re-injected and flooded based on the flood list information (with source squelching). The re-injected ARP-reply/NA keeps all existing non-service-delimiting tags of the original frame.

• For ARP/ND frames that are sent to the CPM, the ARP reply/NA is always unicasted to the subinterface on which the ARP-request/NS arrived, even if the MAC itself has not yet been learned in the MAC table.

If a MAC ACL is bound to the ingress of a bridged subinterface (see the SR Linux ACL and Policy-Based Routing Guide) and proxy-ARP/ND is enabled in the network instance, the rules in the MAC ACL are applied before extraction to the CPM. Consequently, if the MAC ACL drops an ARP packet, it never reaches the CPM.

Disabling dynamic learning for proxy-ARP/ND causes the dynamically learned entries to be flushed from the proxy-ARP/ND table. You can also set an age timer (default disabled) for dynamic entries, after which they are flushed from the proxy table.

In addition, you can set a timer to refresh dynamic entries. At a configured interval (default never) the system generates ARP-requests/NS with the intent to refresh the proxy entry; if no response is received, another one is attempted.

You can configure static entries in the proxy-ARP/ND table. Static entries have higher priority than snooped dynamic and EVPN entries in the table.

A static proxy-ARP/ND entry requires a static or dynamic MAC entry in the MAC table to become active. The static entries are advertised in MAC/IP routes, with the MAC Mobility extended community following the information associated with the MAC entry (static bit or sequence number).

The system does not validate the MAC addresses configured in static entries.

When proxy-arp or proxy-nd is disabled, the configured static entries remain in the proxy table, unlike dynamically learned and EVPN-learned entries, which are flushed from the table.

When proxy-ARP/ND is configured in an EVPN, the PE devices dynamically learn IP-MAC bindings for their local hosts and advertise them in EVPN MAC/IP routes to remote PE devices. The remote PE devices add these IP-MAC bindings to the proxy-ARP/ND table as EVPN-learned entries.

When a host sends an ARP-request or NS for a host on the remote side of the EVPN, if the PE device has the EVPN-learned IP-MAC binding in its proxy-ARP/ND table, it sends back an ARP-reply or NA with the remote host's MAC. If the IP-MAC binding does not exist in the PE device's proxy-ARP/ND table, the ARP-request or NS is flooded in the BD (ARP-request/NS flooding can be optionally disabled). See Layer 2 proxy-ARP example for an illustration of this process.

Proxy-ARP/ND duplicate IP detection is a security mechanism described in RFC 9161 to detect ARP/ND-spoofing attacks. In an ARP/ND-spoofing attack, an attacker sends false ARP/ND messages into a BD, with the goal of associating the attacker's IP address with a target host and directing traffic for that host to the attacker.

The proxy-ARP/ND duplicate IP detection feature monitors changes to active entries in the proxy-ARP/ND table. When an IP move occurs, for example, IP1→MAC1 is replaced by IP1→MAC2 in the table, a monitoring-window timer is started for a default 3 minutes. If a specified number of IP moves (default 5) is detected before the monitoring-window timer expires, the IP is considered to be a duplicate.

When the system detects an IP move in the proxy table, for example, IP1→MAC1 changing to IP1→MAC2, it places the IP1→MAC2 proxy table entry in pending-confirmation state for a maximum of 30 seconds. During the pending-confirmation period, the ARP/ND entry is inactive, and a confirm-message is unicast to MAC1. If no reply from MAC1 is received during the pending-confirmation period, the IP1→MAC2 entry is confirmed as legitimate and becomes active. If a reply from MAC1 is received, then MAC2 is sent a confirm-message. If MAC2 replies, an additional confirm-message is sent to MAC1. If both MAC1 and MAC2 keep replying to the confirm-messages, it triggers the duplicate IP detection procedure for IP1, because the number of IP moves exceeds the maximum allowed during the monitoring window.

When an IP is detected as a duplicate, the proxy table cannot be updated with new dynamic or EVPN-learned entries for the same IP, although you can configure a static entry for the IP. The duplicate IP is subject to this restriction until a configured hold-down-time expires, of which the default is 9 minutes, after which the entry for the IP is removed from the proxy table, and the monitoring process for the IP is restarted.

When you enable proxy-ARP/ND for a MAC-VRF, this creates a table containing proxy-ARP/ND entries learned dynamically by snooping ARP/ND messages, configured statically, or learned from EVPN MAC/IP routes from remote PE nodes. By default, this table can contain up to 250 entries. You can configure the size of this table to be from 1 to 8192 entries.

The system generates a log event when the size of the table reaches 90% of the maximum size and when the table reaches 95% of the maximum size. When the table reaches 100% of its maximum size, entries for an IP can be replaced, that is, a different MAC can be learned and added for the IP, but no new IP entries can be added to the table, regardless of the type (dynamic, static, or EVPN-learned).

RFC 9047 defines an extended community (EC) for EVPN MAC/IP advertisement routes that carry flags related to ARP or ND. This EC includes flags that can indicate to a remote PE router whether an ARP/ND entry learned via EVPN belongs to a host or a router, or if the address is an anycast address. Information from the EC flags can allow remote PE routers configured for proxy ARP/ND to reply to local ARP or ND requests with correct information.

On SR Linux, the RFC 9047 EC is not carried in EVPN MAC/IP advertisement routes by default. You can configure SR Linux to advertise the RFC 9047 EC along with the MAC/IP routes advertised for local static, dynamic, and duplicate proxy-ARP/ND entries. When you enable SR Linux to advertise the RFC 9047 EC, you can also configure how the flags are advertised in EVPN MAC/IP routes and how the flags are set in replies to NS messages for EVPN entries.

This feature is not supported along with IRB interfaces.

The feature must be configured consistently on all PEs attached to the same BD, and in particular attached to the same ES and BD.

At the BGP level, only one EVPN ARP/ND EC is expected to be received along with an EVPN MAC/IP advertisement route. If more than one EVPN ARP/ND EC is received, the router considers only the first one on the list for processing purposes on the PE.

At the EVPN level, the flags are ignored if they come in a MAC/IP route without IP.