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Automatic adjacency SID allocation —SR nodes allocate labels in SRLBs to the IGP adjacencies as SIDs.
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Manual adjacency SID allocation —You can assign adjacency SID by using absolute values or index values. If you use index values, the adjacency SID of a link is the base value of the
SRLB plus the index value for the link.
Dynamic SID allocation through BGP
SR-MPLS expands BGP to advertise prefix SIDs in BGP protocol packets. BGP uses routing policies to assign SIDs to prefixes when redistributing routes. The SIDs uniquely identify the SR nodes. All
SR nodes in the SR domain use BGP to advertise their own prefix SIDs, including the SIDs and SID index values. From received advertisement packets, each SR node derives the prefix SIDs for the advertisers.
BGP prefix SIDs can be exchanged between BGP peers only through IPv4 unicast routes.
Dynamic SID allocation through BGP applies to MPLS VPN inter-AS option C networks.
SID allocation through BGP EPE
The BGP Egress Peer Engineering (BGP EPE) feature assigns BGP peering SIDs to segments across ASs. The device sends BGP peering SIDs to the controller through BGP-LS extensions. The controller orchestrates IGP SIDs and BGP peering SIDs for inter-AS forwarding over optimal paths.
You can manually specify the BGP peering SIDs to be assigned to the BGP peers or peer groups or let the device randomly assign these SIDs.
BGP EPE supports the following types of BGP peering SIDs:
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Peer-Node-SID —Identifies a peer node. Each BGP session is assigned a Peer-Node-SID. An
EBGP peer session established based on a loopback interface might use multiple physical links.
The Peer-Node-SID for the EBGP peer therefore might have multiple outgoing interfaces. The device will load-share traffic among these outgoing interfaces when it forwards the traffic based on the Peer-Node-SID.
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Peer-Adj-SID —Identifies an adjacency to a peer. An EBGP peer session established based on a loopback interface might use multiple physical links. Each physical link will be assigned a
Peer-Adj-SID. The device forwards traffic through a specific outgoing interface when it forwards the traffic based on a Peer-Adj-SID.
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Peer-Node-Adj-SID —Identifies a peer node or one or multiple adjacencies to a peer.
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Peer-Set-SID —Identifies a set of peers. BGP EPE supports adding a group of peers to a set and assigning the set a Peer-Set-SID. The device will load-share traffic among the peers in the set when it forwards the traffic based on a Peer-Set-SID. A Peer-Set-SID identifies the set of which Peer-Node-SIDs or Peer-Adj-SIDs are members.
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