Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 640

Limiting the Source-Active Cache Set the upper limit of the number of active sources that the system caches. The default active source limit is 500K messages. When the total number of active sources reaches the specified limit, subsequent active sources are dropped even if they pass the reverse path forwarding (RPF) and policy check. To limit the number of sources that SA cache stores, use the following command. • Limit the number of sources that can be stored in the SA cache. EXEC Privilege mode show ip msdp sa-limit If the total number of active sources is already larger than the limit when limiting is applied, the sources that are already in the OS are not discarded. To enforce the limit in such a situation, use the clear ip msdp sa-cache command to clear all existing entries. Clearing the Source-Active Cache To clear the source-active cache, use the following command. • Clear the SA cache of all, local, or rejected entries, or entries for a specific group. CONFIGURATION mode clear ip msdp sa-cache [group-address | local | rejected-sa] Enabling the Rejected Source-Active Cache To cache rejected sources, use the following command. Active sources can be rejected because the RPF check failed, the SA limit is reached, the peer RP is unreachable, or the SA message has a format error. • Cache rejected sources. CONFIGURATION mode ip msdp cache-rejected-sa Accept Source-Active Messages that Fail the RFP Check A default peer is a peer from which active sources are accepted even though they fail the RFP check. Referring to the following illustrations: • In Scenario 1, all MSPD peers are up. • In Scenario 2, the peership between RP1 and RP2 is down, but the link (and routing protocols) between them is still up. In this case, RP1 learns all active sources from RP3, but the sources from RP2 and RP4 are rejected because the reverse path to these routers is through Interface A. • In Scenario 3, RP3 is configured as a default MSDP peer for RP1 and so the RPF check is disregarded for RP3. • In Scenario 4, RP1 has a default peer plus an access list. The list permits RP4 so the RPF check is disregarded for active sources from it, but RP5 (and all others because of the implicit deny all) are subject to the RPF check and fail, so those active sources are rejected. 640 Multicast Source Discovery Protocol (MSDP)