PIM RP Troubleshooting
Load pim.rp.tshoot.cfg
Currently, R9 is the RP via BSR. The operator has been asked to configure R10 as the new RP, using static RP assignment.
The operator has configured R10 as a static RP and it has brought up its decap tunnel, so that looks correct. The operator has also configured R10 as the static RP on R5 and XR3. However, every group that R2 or R4 joins still uses R9 as the RP.
Explain the issue and find a way to fix it.
Answer
Explanation
The problem is that BSR and AutoRP mappings take precedence over static RP mappings. This is somewhat opposite how static definitions usually work. For example, a static unicast route always has a better AD than any dynamically learned unicast route.
The command show pim rp mapping doesn’t show which RP is really in use.
Note that on IOS-XE, using the show ip pim rp-hash command is not a way to verify whether a static RP is used. This command only shows the result among BSR-learned RPs. This command will always output a BSR-learned RP address no matter whether the override keyword is associated with the static RP.
The problem can also be verified in the MRIB table. All ASM groups are using R9 as the RP:
We must use the override keyword to force the static RP mapping to take precedence over dynamically learned RPs (BSR or AutoRP).
The PIM RP mapping output now shows that the static mapping has override on IOS-XE.
On IOS-XR, there is no override indication. The static mapping is now placed above the BSR mapping. I’m unsure if that is coincidence or because the static mapping is now taking precedence.
We now see that MRIB entries use R10 as the RP:
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