The P2MP LSP ping complies to RFC 6425, Detecting Data Plane Failures in Point-to-Multipoint Multiprotocol Label Switching (MPLS) - Extensions to LSP Ping.
An LSP ping can be generated by entering the following OAM command:
- oam p2mp-lsp-ping lsp-name [p2mp-instance instance-name [s2l-dest-addr ip-address [...up to 5 max]]] [fc fc-name [profile {in | out}]] [size octets] [ttl label-ttl] [timeout timeout] [detail]The echo request message is sent on the active P2MP instance and is replicated in the data path over all branches of the P2MP LSP instance. By default, all egress LER nodes which are leaves of the P2MP LSP instance replies to the echo request message.
The user can reduce the scope of the echo reply messages by explicitly entering a list of addresses for the egress LER nodes that are required to reply. A maximum of 5 addresses can be specified in a single execution of the p2mp-lsp-ping command. If all 5 egress LER nodes are router nodes, they can parse the list of egress LER addresses and reply. RFC 6425 specifies that only the top address in the P2MP egress identifier TLV must be inspected by an egress LER. When interoperating with other implementations, the router egress LER responds if its address is anywhere in the list. Furthermore, if another vendor implementation is the egress LER, only the egress LER matching the top address in the TLV may respond.
If the user enters the same egress LER address more than once in a single p2mp-lsp-ping command, the head-end node displays a response to a single one and displays a single error warning message for the duplicate ones. When queried over SNMP, the head-end node issues a single response trap and issues no trap for the duplicates.
The timeout parameter should be set to the time it would take to get a response from all probed leaves under no failure conditions. For that purpose, its range extends to 120 seconds for a p2mp-lsp-ping from a 10 second lsp-ping for P2P LSP. The default value is 10 seconds.
The router head-end node displays a ‟Send_Fail” error when a specific S2L path is down only if the user explicitly listed the address of the egress LER for this S2L in the ping command.
Similarly, the router head-end node displays the timeout error when no response is received for an S2L after the expiry of the timeout timer only if the user explicitly listed the address of the egress LER for this S2L in the ping command.
The user can configure a specific value of the ttl parameter to force the echo request message to expire on a router branch node or a bud LSR node. The latter replies with a downstream mapping TLV for each branch of the P2MP LSP in the echo reply message. Note that a maximum of 16 downstream mapping TLVs can be included in a single echo reply message. It also sets the multipath type to zero in each downstream mapping TLV and not include any egress address information for the reachable egress LER nodes for this P2MP LSP.
If the router ingress LER node receives the new multipath type field with the list of egress LER addresses in an echo reply message from another vendor implementation, it ignores but not cause an error in processing the downstream mapping TLV.
If the ping expires at an LSR node which is performing a re-merge or cross-over operation in the data path between two or more ILMs of the same P2MP LSP, there is an echo reply message for each copy of the echo request message received by this node.
The output of the command without the detail parameter specified provides a high-level summary of error codes or success codes received.
The output of the command with the detail parameter specified shows a line for each replying node as in the output of the LSP ping for a P2P LSP.
The display is delayed until all responses are received or the timer configured in the timeout parameter expired. No other CLI commands can be entered while waiting for the display. A control-C (^C) command aborts the ping operation.
For more information about P2MP, see the 7450 ESS, 7750 SR, 7950 XRS, and VSR MPLS Guide.