Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.112.0P1 - Page 587

Important Points to Remember • Destination address of the mtrace query message can be either a unicast or a multicast address. NOTE: When you use mtrace to trace a specific multicast group, the query is sent with the group's address as the destination. Retries of the query use the unicast address of the receiver. • When you issue an mtrace without specifying a group address (weak mtrace), the destination address is considered as the unicast address of the receiver. • If the CLI session is terminated after the mtrace command is issued, then the response is ignored. • System ignores any stray mtrace responses that it receives. • Duplicate query messages as identified by the IP source, and Query ID (tuple) are ignored. However, duplicate request messages are not ignored in a similar manner. • The system supports up to a maximum of eleven mtrace clients at a time. NOTE: The maximum number of clients are subject to performance restrictions in the new platform. • Mtrace supports only IPv4 address family. Printing Multicast Traceroute (mtrace) Paths Dell Networking OS supports Multicast traceroute. MTRACE is an IGMP-based tool that prints the network path that a multicast packet takes from a source to a destination, for a particular group. Dell Networking OS has mtrace client and mtrace transit functionality. • MTRACE Client - an mtrace client transmits mtrace queries and print the details from received responses. • MTRACE Transit - when a Dell Networking system is an intermediate router between the source and destination in an MTRACE query, Dell Networking OS computes the RPF neighbor for the source, fills in the request, and forwards the request to the RPF neighbor. When a Dell Networking system is the last hop to the destination, Dell Networking OS sends a response to the query. To print the network path, use the following command. • Print the network path that a multicast packet takes from a multicast source to receiver, for a particular group. EXEC Privilege mode mtrace multicast-source-address multicast-receiver-address multicast-group-address From source (?) to destination (?) |Hop| OIF IP |Proto| Forwarding Code |Source Network/Mask| 0 "destination ip(to)" --> Destination -1 "Outgoing intf addr" "Proto" "Err/fwd code if present" "Src Mask" -2 "Outgoing intf addr" "Proto" "Err/fwd code if present" "Src Mask" . . -"n" "source ip(from)" --> Source The mtrace command traverses the path of the response data block in the reverse direction of the multicast data traffic. As a result, the tabular output of the mtrace command displays the destination details in the first row, followed by the RPF router details along the path in the consequent rows, and finally the source details in the last row. The tabular output contains the following columns: • Hop - a hop number(counted negatively to indicate reverse-path) • OIF IP - outgoing interface address • Proto - multicast routing protocol • Forwarding code - error code as present in the response blocks Multicast Features 587