Configuring BGP EPE

In addition to enabling the BGP-LS route family for a BGP neighbor, the following CLI is required to send the Egress Peering Segments described in BGP Egress Peer Engineering using BGP Link State using the NLRI Type 2 with protocol ID set to BGP-EPE.

CLI syntax

configure>router>bgp
   egress-peer-engineering {  
     admin-state {enable | disable}
   }

When egress-peer-engineering is administratively enabled, BGP registers with SR and the router starts advertising any peer node and peer adjacency SIDs in BGP-LS.

To allocate peer node and peer adjacency SIDs, use the following syntax to configure the egress-engineering command and enable BGP-EPE for a BGP neighbor or group.

CLI syntax

configure>router>bgp
  group
    neighbor <a.b.c.d> {
      egress-engineering {
        admin-state {enable | disable}
      }

configure>router>bgp
  group
    egress-engineering {
      admin-state {enable | disable}
    }

The BGP egress-engineering at the neighbor level overrides the group level configuration. When a neighbor does not have an egress-engineering configuration context, the group configuration is inherited in the following cases.

When a neighbor has egress-engineering configured and in the default disabled state, egress-engineering is disabled for the neighbor, irrespective of the disabled, enabled, or no-context configuration at the group level. When a neighbor has egress-engineering configured and enabled, egress-engineering is enabled for the neighbor, irrespective of the disabled, enabled, or no-context configuration at the group level.

By default, enabling egress-engineering at the peer or group level causes SID values (MPLS labels) to be dynamically allocated for the peer node segment and the peer adjacency segments. Although the labels are assigned when the neighbor or group is configured, they are not programmed until the adjacency comes up. Peer node segments are derived from the BGP next hops used to reach a specific peer. If the node reboots, these dynamically allocated label values may change and are re-announced in BGP-LS.

If a BGP neighbor goes down, the router advertises a delete for all SIDs associated with the neighbor and deprograms them from the IOM. However, the label values for the SIDs are not released and the router re-advertises the same values when the BGP neighbor comes back up.

If a BGP neighbor is deleted from the configuration or is shut down, or egress-engineering is disabled, the router advertises a delete for all SIDs associated with the neighbor and deprograms them from the IOM. The router also releases the label values for the SIDs.

Parent topic: BGP Egress Peer Engineering using BGP Link State