Re: mtrace command on Nexus 5548

tobin_jim · ‎01-22-2014

I have two Nexus 5548s connected together in a VPC setup. All the VPC vlans are setup with HSRP on them between the swtiches. There is a non-VPC vlan on both devices that is used as a layer 3 adjency for OSPF area 0. This layer 3 link is done over a vlan over the vPC peer-link.

One switch, 5548-01, has two layer 3 ports to other Nexus switches over an Ethernet WAN. These layer 3 ports are running in OSPF area 0 also.

I am using the mtrace command to test our multicast setup. Can anyone help interpret the output below. I have added my coments in red.

5548-02# mtrace 10.100.0.5

Mtrace from 10.100.0.5 to 10.110.119.254 via group 0.0.0.0

Querying full reverse path... * switching to hop-by-hop:

0 ? (10.110.119.254)

-1 ? (10.110.119.254) PIM [default] (Source interface)

-2 ? (10.130.119.253) PIM !RPF!? (10.255.255.53) [default]

(10.110.119.253 is the peer HSRP address for this Vlan. 10.255.255.53 is the layer 3 OSPF Area Link)

-3 * * ? (10.255.255.25) PIM [default] (WAN connection from 5548-01 to remote Nexus switch)

-4 * * ? (10.255.255.17) PIM

-5 * ? (10.120.255.5) PIM

-6 ? (10.100.0.5)

Round trip time 11 ms; total ttl of 5 required.

It looks to me like the reverse path query process eventualluy works but there is some bouncing between the shared vlan interfaces form the source vlan (10.110.119.254 and 10.110.119.253). Is this expected?

What does the "!RPF!?" mean?

James Yeo · ‎12-11-2018

I would suggest adding a PIM priority command on the active interface on the HSRP group. This will keep your path alignment.

Sets the designated router (DR) priority that is advertised in PIM hello messages on this interface. On a multi-access network with multiple PIM-enabled routers, the router with the highest DR priority is elected as the DR router. If the priorities match, the software elects the DR with the highest IP address. The DR originates PIM register messages for the directly connected multicast sources and sends PIM join messages toward the rendezvous point (RP) for directly connected receivers. Values range from 1 to 4294967295. The default is 1.