Troubleshooting IP Multicast Routing
Your primary weapon when attacking problems in IP multicast internetworks is a solid understanding of the IP multicast protocols. Without that, no number of troubleshooting tools will help you wend your way through the often confusing, sometimes complex behaviors of IP multicast to the root of a particular problem. And understanding a single protocol is not enough. You also must understand how PIM, IGMP, and unicast routing all interact.
If you have been closely following the troubleshooting sections of each chapter of both Volume I and this volume, you should by now have a well-developed grasp of the approaches and techniques necessary for resolving problems in routed internetworks. So rather than present further case studies illustrating troubleshooting techniques, this section demonstrates the use of the several specialized tools provided for analyzing multicast internets.
Throughout this chapter, you have seen various show and debug commands that are useful for observing the behavior of IP multicast routing on Cisco routers. Table 6-2 lists the show commands available to you, and Table 6-3 lists the important multicast debug commands. Just as show ip route is the primary source of information when troubleshooting IP unicast routing, show ip mroute is the primary source of information when troubleshooting IP multicast routing.
Table 6-2 Important show Commands for Troubleshooting IP Multicast
|
Command |
Description |
|
show ip igmp groups [group-name I |
Displays the addresses of groups that have |
|
group-address I type number] |
members on the router's interfaces. |
|
show ip igmp interface [type number] |
Displays relevant details of the IGMP-enabled |
|
interface. |
|
|
show ip mcache [group [source]] |
Displays the multicast contents of the fast- |
|
switching cache. |
show ip mroute [group-name I group- Displays the contents of the multicast routing address] [source] [summary] [count] table,
[active kbps]
show ip mroute [group-name I group- Displays the contents of the multicast routing address] [source] [summary] [count] table,
[active kbps]
|
show ip pim bsr |
Displays information about PIM bootstrap |
|
routers. |
|
|
show ip pim interface [type number] |
Displays relevant details of PIM-enabled |
|
[count] |
interfaces. |
|
show ip pim neighbor [type number] |
Displays PIM neighbors. |
|
show ip pim rp [group-name 1 group- |
Displays the known RPs, and the groups |
|
address 1 mapping] |
mapped to the RPs. |
|
show ip pim rp-hash group |
Displays the RP for the group specified. |
show ip rpf {source-address I name] Displays details of how the router is determining RPF information.
|
Command |
Description |
|
debug ip icmp [hostname 1 |
Displays IGMP protocol activity. |
|
group _address] |
|
|
debug ip mcache [hostname 1 |
Displays multicast caching operations. |
|
group_address] |
|
|
debug ip mpacket |
Displays multicast packets transiting the router. |
|
[standard_access_list 1 |
|
|
extended_access_list] [hostname 1 |
|
|
group _address] [detail] |
|
|
debug ip mrouting [hostname 1 |
Displays multicast routing table activity. |
|
group_address] |
debug ip pim [hostname I Displays PIM activity and events.
group_address] [auto-rp] [bsr]
Continue reading here: Using mrinfo
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