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Switch(Config-If-Vlan2)# ip pim sparse-mode
Switch(Config-If-Vlan2)#exit
Switch(config)#interface vlan 3
Switch(Config-If-Vlan3)# ip pim sparse-mode
Switch(Config-If-Vlan3)#exit
Switch(config)#access-list 1 permit 224.1.1.1 0.0.0.255
Switch(config)#ip multicast ssm range 1
48.6.4 PIM-SSM Troubleshooting
In configuring and using PIM-SSM Protocol, PIM-SSM Protocol might not operate normally caused by
physical connection or incorrect configuration. Therefore, the user should pay attention to the following
issues:
Assure that physical connection is correct;
Assure the Protocol of Interface and Link is UP (use show interface command);
Assure that PIM Protocol is enabled in Global Mode (use ip pim multicast-routing);
Assure that PIM-SSM is configured on the interface (use ip pim sparse-mode);
Assure that SSM is configured in Global Mode;
Multicast Protocol requires RPF check using unicast routing, therefore the correctness of unicast
routing must be assured beforehand.
If all attempts including check are made but the problems on PIM-SSM can’t be solved yet, then use debug
commands such debug pim event/debug pim packet please, and then copy DEBUG information in 3
minutes and send to Technology Service Center.
48.7 DVMRP
48.7.1 Introduction to DVMRP
DVMRP Protocol, namely, is “Distance Vector Multicast Routing Protocol”. It is a Multicast Routing Protocol in
dense mode, which sets up a Forward Broadcast Tree for each source in a manner similar to RIP, and sets up
a Truncation Broadcast Tree, i.e. the Shortest Path Tree to the source, for each source through dynamic
Prune/Graft.
Some of the important features of DVMRP are:
1. The routing exchange used to determine reverse path checking information is based on distance
vector (in a manner similar to RIP)
2. Routing exchange update occurs periodically (the default is 60 seconds)
3. TTL upper limit = 32 hops (and that RIP is 16)
4. Routing update includes net mask and supports CIDR
In comparison with Unicast routing, Multicast routing is a kind of reverse routing (that is, what you are
interested in is where the packets are from but not where they go), thus the information in DVMRP routing
table is used to determine if an input Multicast packet is received at the correct interface. Otherwise, the
packet will be discarded to prevent Multicast circulation.
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