BGP Egress Peer Engineering (EPE) allows for the traffic-engineered creation of egress links from a source domain to an external domain. These links function as a BGP peer between two ASBR routers, which may be configured as E-BGP or I-BGP. When I-BGP is used, NSP does not track or know the underlying path the I-BGP peer session is representing and forwarding over. The BGP peer can also be associated with a label and used within a segment-routed path. When used in this way, the policy that controls the links that are used is defined at the source router as part of the label stack in the path, which can be computed by NSP. EPE links are represented as a dashed line within the path control network map, as they are virtual links that can span over multiple hops. The links are automatically collapsed for bi-directional representation if the reverse link direction is known.

All EPE links must contain a peer node SID for the remote peer, but may also contain an adjacency SID or peer SID set. Since NSP does not support SID sets, the priorities for specifying the hop in the ERO are:

1. Adjacency SID, if it exists

2. Peer node SID

If a peer node SID is not found, the link is considered invalid.

Note: Due to limitations in current router implementations, NSP assumes that the EPE SID cannot be used as the top SID in a label stack.

The following is an example of the required node configuration:

A:s111_11_111_Both>config>router>bgp# info

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

family ipv4 bgp-ls

min-route-advertisement 3

link-state-import-enable

egress-peer-engineering

no shutdown

exit

group "abr"

peer-as 400

egress-engineering

no shutdown

exit

neighbor x.x.x.x

egress-engineering

no shutdown

exit

exit

The bandwidth capacity of an EPE link is not advertised. If the bandwidth capacity of an EPE link can be known (for example, if it is provided in the BGP-LS advertisement or is NBI configured), NSP will manage and track bandwidth against it as it does other links, but it will not be mapped to any underlying IGP. If the bandwidth capacity of an EPE link cannot be known, NSP will not enforce bandwidth constraints on the link, nor will it perform any optimizations.

BGP-LS does not provide any TE attributes for EPE links. Users can provide these using the following REST API:

https://<NSP_cluster>:443/sdn/api/v4/nsp/net/l3/link/<Link_ID>

Where

NSP_cluster is the IP address of the NSP cluster

Link_ID is the ID of the EPE link

For more information, see the Network Developer Portal.