A PW can be configured to use any available LSP to the peer endpoint IP address, or the PW can be configured to use one or more specific named LSPs.
In either case, the LSP has to egress (terminate) at the remote endpoint. In the case of an LDP LSP, the LSP's FEC has to be a /32 prefix length to the endpoint IP address. In the case of an RSVP-TE LSP or static LSP, the destination address has to be that of the remote endpoint. When configured to use any available LSP, MPLS (Multiprotocol Label Switching) gives preference to RSVP-TE LSPs, then to LDP LSPs, and lastly, to static LSPs. As a single LSP is chosen to carry the PW traffic, if multiple LSPs of the chosen type exist, the decision of which LSP of this type to use is non-deterministic.
The configure l2vpn [vpls vpls_name | vpws vpws_name] peer ipaddress [add | delete] mpls lsp lsp_name command forces the PW to use the specified named LSP. If multiple named LSPs are configured, only one is used to carry the PW. The decision of which of the multiple configured LSPs to use is non-deterministic.
RSVP-TE can be configured to allow specific types of traffic on an LSP. By default, LSPs are used to transport all traffic. Optionally, named LSPs can be configured to allow only IP traffic or only VPN traffic. This can be used to control the LSP selection for specific types of packets. For example, if both LDP and RSVP-TE LSPs exist and the RSVP-TE LSPs are configured to transport only VPN traffic, all IP traffic is forwarded using LDP LSPs. Since RSVP-TE LSPs are preferred over LDP LSPs, VPN traffic flows over the RSVP-TE LSPs. The following command configures this behavior for the specified RSVP-TE LSP:
configure mpls rsvp-te lsp lasp_name transport ip-traffic deny
For more information see Pseudowire Label Switch Path Load Sharing.
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