Supported Platforms
Configuring Inter-domain P2MP LSPs
An inter-domain P2MP LSP is a P2MP LSP that has one or more sub-LSPs (branches) that span multiple domains in a network. Examples of such domains include IGP areas and autonomous systems (ASs). A sub-LSP of an inter-domain P2MP LSP may be intra-area, inter-area, or inter-AS, depending on the location of the egress node (leaf) with respect to the ingress node (source).
On the ingress node, a name is assigned to the inter-domain P2MP LSP and shared by all constituent sub-LSPs. Each sub-LSP is configured separately, with its own egress node and optionally an explicit path. The location of the egress node of the sub-LSP with respect to the ingress node determines whether the sub-LSP is intra-area, inter-area, or inter-AS.
Inter-domain P2MP LSPs can be used to transport traffic in the following applications in a multi-area or multi-AS network:
- Layer 2 broadcast and multicast over MPLS
- Layer 3 BGP/MPLS VPN
- VPLS
On each domain boundary node (ABR or ASBR) along the path of the P2MP LSP, the expand-loose-hop statement must be configured at the [edit protocols mpls] hierarchy level so that CSPF can extend a loose-hop ERO (usually the first entry of the ERO list carried by RSVP Path message) towards the egress node or the next domain boundary node.
CSPF path computation for inter-domain P2MP LSPs:
- CSPF path computation is supported on each sub-LSP for inter-domain P2MP LSPs. A sub-LSP may be intra-area, inter-area, or inter-AS. CSPF treats an inter-area or inter-AS sub-LSP in the same manner as an inter-domain P2P LSP.
- On an ingress node or a domain boundary node (ABR or ASBR), CSPF can perform an Explicit Route Object (ERO) expansion per-RSVP query. The destination queried could be an egress node or a received loose-hop ERO. If the destination resides in a neighboring domain that the node is connected to, CSPF generates either a sequence of strict-hop EROs towards it or a sequence of strict-hop EROs towards another domain boundary node that can reach the destination.
- If RSVP fails to signal a path through a previously selected domain bounday node, RSVP attempts to signal a path through other available domain boundary nodes in a round-robin fashion.
- When a sub-LSP is added or removed to or from an inter-domain P2MP LSP, causing its path (branch) to be merged or pruned with or from the current P2MP tree, the paths being taken by the other sub-LSPs should not be affected, helping to prevent traffic disruption on those sub-LSPs.
Be aware of the following when deploying inter-domain P2MP LSPs in your network:
- Periodic path re-optimization is supported for inter-domain P2MP LSPs on ingress nodes. It can be turned on for an inter-domain P2MP LSP by configuring the optimize-timer statement at the [edit protocols mpls label-switched-path lsp-name] hierarchy level with the same interval for every sub-LSP.
- Only link protection bypass LSPs are supported for inter-domain P2MP LSPs. To enable it for an inter-domain P2MP LSP, link-protection must be configured for all sub-LSPs and on all of the RSVP interfaces that the P2MP LSP might travel through.
- Only OSPF areas are supported for inter-domain P2MP LSPs. IS-IS levels are not supported.
