Viewing data for a specified flow (multicast group)

Syntax:


show ip [mroute] [multicast-ip-addr source-ip-addr]

Lists the following data for the specified multicast flow (source-group pair):

[Group Address]

The multicast group IP address for the specified flow.

[Source Address]

The source IP address for the specified flow.

[neighbor]

Lists the IP address of the upstream next-hop router running PIM-DM; that is, the router from which the routing switch is receiving datagrams for the current multicast group.

This value is 0.0.0.0 if the routing switch has not detected the upstream next-hop router's IP address. This field is empty if the multicast server is directly connected to the routing switch.

[VLAN]

The interface on which the router receives the multicast flow.

[Up Time (Sec)]
The elapsed time in seconds since the routing switch learned the information for the current instance of the indicated multicast flow.
NOTE:

On an originator router, when a forwarding flow moves to a non-forwarding state (i.e. when pruned) the Up Time value for that flow is reset to 0.

[Expire Time (Sec)]

An mroute which is in a forwarding state — one which represents an active, connected flow for which there are downstream routers and/or locally connected hosts interested in the flow — does not expire. When other PIM-DM routers or locally connected hosts are no longer interested in an active flow, the related mroute on an originator router moves to a blocking state, and an mroute in this state does not expire either. In both cases the mroute is only removed by the system when it is no longer needed and so the displayed value for expire time in these situations is not meaningful.

For an mroute on an originator router whose flow is no longer active - including mroutes on non-originators whose flow has been pruned — expire time indicates when the mroute entry will eventually be cleared.

Multicast Routing Protocol

Identifies the multicast routing protocol through which the current flow was learned.

Unicast Routing Protocol

Identifies the IP routing protocol through which the routing switch learned the upstream interface for the current multicast flow. The listed protocol will be one of the following:

  • RIP

  • connected

  • OSPF

  • static route

  • other

Metric

Indicates the path cost upstream to the multicast source. Used when multiple multicast routers contend to determine the best path to the multicast source. The lower the value, the better the path.

Metric Pref

Used when multiple multicast routers contend to determine the path to the multicast source. When this value differs between routers, PIM selects the router with the lowest value. If Metric Pref is the same between contending multicast routers, then PIM selects the router with the lowest Metric value to provide the path for the specified multicast traffic. (Different vendors assign differing values for this setting.)

Asset Timer

The time remaining until the router ceases to wait for a response from another multicast router to negotiate the best path back to the multicast source. If this timer expires without a response from any contending multicast routers, then the router assumes it is the best path, and the specified multicast group traffic will flow through the router.

RP Tree

This field is not relevant to PIM-DM and will always display No.

Downstream interfaces

For each downstream interface the following information is shown:

[VLAN]
Lists the

[VID]
of the VLAN that the routing switch is using to send the outbound packets of the current multicast flow to the next-hop router.
[state]

Indicates whether the outbound VLAN and next-hop router for the current multicast flow are receiving datagrams.

Pruned

The routing switch has not detected any joins from the current multicast flow and is not currently forwarding datagrams in the current VLAN.

Forwarding

The routing switch has received a join for the current multicast flow and is forwarding datagrams in the current VLAN.

Up Time (Sec)

The natural state of a downstream interface in PIM-DM is to forward multicast flows and DM will flood a new flow out all interfaces on a router where there are connected PIM-DM neighbors and/or joined hosts. If there are ultimately no receivers for the flow downstream, the flow will be pruned back to the originator router. This prune state is maintained on all PIM-DM routers by state refresh message sends by the originator and corresponding prune replies from downstream routers. However if a prune reply is not received (i.e. there is now a receiver), expire time indicates how long before the interface will return to a forwarding state.

Expire Time (sec)

The natural state of a downstream interface in PIM-DM is to forward multicast flows and DM will flood a new flow out all interfaces on a router where there are connected PIM-DM neighbors and/or joined hosts. If there are ultimately no receivers for the flow downstream, the flow will be pruned back to the originator router. This prune state is maintained on all PIM-DM routers by state refresh message sends by the originator and corresponding prune replies from downstream routers. However if a prune reply is not received (i.e. there is now a receiver), expire time indicates how long before the interface will return to a forwarding state.

Output for routing switch "#1" in Multicast network with a multinetted VLAN

A populated neighbor field indicates that the multicast server is directly connected to the routing switch (neighbor field is highlighted in bold below.)

switch(config)# show ip mroute 239.255.255.5 10.27.30.2
 IP Multicast Route Entry
  Group Address  : 239.255.255.5
  Source Address : 10.27.30.2
  Source Mask    : 255.255.255.0
  Neighbor       : 10.30.229.1
  VLAN           : 27
  Up time (sec)     : 408
  Expire Time (sec) : 150
  Multicast Routing Protocol : PIM-DM 
  Unicast Routing Protocol   : rip

Downstream Interfaces
  VLAN State      Up time (sec)      Expire Time (sec)
  ---- ---------- ------------------ -----------------
  28   pruned     408                98