BGP and routing policy extensions for EVPN

SR Linux supports Multi-Protocol BGP with AFI/SAFI EVPN. The following BGP features are relevant to EVPN in a VXLAN network:

• The EVPN address family can use eBGP or iBGP.

• eBGP multi-hop is not supported on SR Linux; however, local-as override is supported for iBGP per session.

• A supported configuration/design with eBGP is eBGP with local-as override on the session to an iBGP RR.

• Rapid-update and rapid-withdrawal for EVPN family are supported and are always expected to be enabled, especially along with multi-homing. Note that rapid-update is address-family specific, while rapid-withdrawal is generic for all address families.

• The BGP keep-all-routes option is supported for EVPN to avoid route-refresh messages attracting all EVPN routes when a policy changes or bgp-evpn is enabled.

• The receive-ipv6-next-hops option does not apply to the EVPN address family.

• The prefix-limit max-received-routes and threshold options are supported for EVPN.

• The command network-instance protocols bgp route-advertisement wait-for-fib-install does not apply to EVPN.

• SR Linux BGP resolves BGP-EVPN routes’ next-hops in the network-instance default route-table. If the next-hop is resolved, BGP can mark the route as u*> (u=used, *=valid, >=best) and send the route to evpn_mgr if needed or reflected to other peers.

SR Linux includes support for applying routing policies to EVPN routes. You can specify the following match conditions in a policy statement:

• Match routes based on EVPN route type.

• Match routes based on IP addresses and prefixes via prefix-sets for route types 2 and 5.

• Match routes based BGP encapsulation extended community.

• Match routes based on configured admin-tags

For information about configuring routing policies on SR Linux, see the SR Linux Configuration Basics Guide.

The following considerations apply to routing policies for EVPN:

• For IBGP neighbors, EVPN routes are imported and exported without explicit configuration of any policy at either the BGP or network-instance level.

• For EBGP neighbors, by default, routes are imported or exported based on the ebgp-default-policy configuration.

• When an explicit import/export route-target is configured in a network-instance bgp-instance, and an import/export policy is also configured on the same bgp-instance, the configured policy is used, and its route-target is added to the imported/exported route.

• When a network-instance policy and a peer policy are applied, they are executed as follows:

  • For export, the network-instance export policy is applied first, and the peer policy is applied afterwards (sequentially).

  • For import, peer import policy is applied first and network-instance import policy is applied afterwards (sequentially).

• Only one network-instance export and import policy is supported.