Cisco Multicast Troubleshooting Tips.
Most of time multicast issue is related with Reverse Path Forwarding (RPF) issue
1. Check multicast configuration
– Make sure ‘ ip multicast-routing ‘ is enabled
– Verify multicast configuration on each interfaces
ex) Cisco_Multicast# show ip pim interface
2. Find out multicast route
– Private multicast route is normaly 239.0.0.0/8 range.
ex) 239.100.100.1 ( try ‘ show ip mroute ‘ )
– If you don’t have one, create one (fake) using below command
Cisco_Multicast#conf t
Cisco_Multicast(config)# int fa0/1 ; wherever multicast server would be.
Cisco_Multicast(config-if)# ip igmp join-group 239.100.100.1
3. Find RP (if spare or spare-dense mode is being used)
– From running configuration or ‘ show ip mroute ‘
4. Check multicast routing table for multicast group IP
Cisco_Multicast# show ip mroute 239.100.100.1
IP Multicast Routing Table Flags: D - Dense, S - Sparse, C - Connected, L - Local, P - Pruned R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT M - MSDP created entry, X - Proxy Join Timer Running A - Advertised via MSDP Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 239.100.100.1), 00:01:15/00:02:59, RP 10.10.10.1, flags: DJC Incoming interface: VLAN 100, RPF nbr 20.20.20.1 Outgoing interface list: Ethernet3/1, Forward/Sparse-Dense, 00:01:15/00:00:00 Ethernet3/2, Forward/Sparse-Dense, 00:00:58/00:00:00
5. Check RPF information for RP (in this case 10.10.10.1)
Cisco_Multicast# show ip rp 10.10.10.1 RPF information for ? (10.10.10.1) RPF interface: Ethernet4/0 RPF neighbor: ? (0.0.0.0) RPF route/mask: 10.10.10.1/32 RPF type: unicast (static) RPF recursion count: 0 Doing distance-preferred lookups across table
6. Check unicast routing table for RP
Cisco_Multicast# show ip route 10.10.10.1 Routing entry for 10.10.10.1/32 Known via "static", distance 1, metric 0 (connected) Routing Descriptor Blocks: * directly connected, via Ethernet2/0 Route metric is 0, traffic share count is 1
** Mismatching Multicast feed path and unicast route path.
– Cisco IOSĀ® calculates the RPF interface in this way. Possible sources of RPF information are Unicast Routing Table, MBGP routing table, DVMRP routing table and Static Mroute table
1. Static mroutes
2. DVMRP routes
3. MBGP routes
4. Unicast routes
7. Applying static mroute
Cisco_Multicast(config)# ip mroute 10.10.10.1 255.255.255.255 Ethernet2/0
Cisco_Multicast# show ip rp 10.10.10.1 RPF information for ? (10.10.10.1) RPF interface: Ethernet2/0 RPF neighbor: ? (0.0.0.0) RPF route/mask: 10.10.10.1/32 RPF type: unicast (static) RPF recursion count: 0 Doing distance-preferred lookups across table
8. Extra command
Cisco_Multicast# show ip mroute 239.100.100.1 count
Cisco_Multicast# debug ip mpacket 224.1.1.1
Cisco_Multicast# show ip igmp group
Cisco_Multicast# show ip igmp interface
Cisco_Multicast# show ip pim rp 239.100.100.1
Cisco_Multicast# show ip pim rp map
Cisco_Multicast# show ip pim interface
Cisco_Multicast# show ip pim neighbor
Cisco_Multicast# show ip traffic
Cisco_Multicast# show ip mroute summary
Cisco_Multicast# show ip mroute active ; To check whether the router recognizes any active traffic
Cisco_Multicast# mstat [Source IP] [Destination IP] [Multicast Group IP]
Cisco_Multicast# mrinfo
Cisco_Multicast# mtrace [Source IP] [Destination IP] [Multicast Group IP]
Cisco_Multicast# ping [Multicast Group IP]
Cisco_Multicast# show ip rpf [Destination IP]
Cisco_Multicast# show ip mcache ; It shows source IP and group IP
Cisco_Multicast# show ip mroute count
Debugging commands
Cisco_Multicast# debug IP IGMP
Cisco_Multicast# debug IP mpacket
Cisco_Multicast# debug IP mrouting
Cisco_Multicast# debug IP PIM
Ref. http://www.cisco.com/en/US/tech/tk828/technologies_tech_note09186a0080094b55.shtml