R&S Quick Notes – Multicast & IPv6


  • BSR is also commonly referred to as PIMv2.
  • Pay special attention to when using Frame-Relay non-broadcast types. Multicast will not work. Tunnels might be needed.
  • BSR – when multiple c-RP announces same groups, a longer match will be used to determine the RP, regardless of the RP priority set.
  • With TTL scoping, if the Packet TTL >= Interface TTL, then the packet is forwarded, else dropped.
  • GRE-tunnel –  If the unicast source is reachable via tunnel, a RPF failure will occur. Correct with Mroute.
  • Know how to spot RPF failures.
  • Multicast Filtering:

1. Q – Prevent PIM neighbor establishments, but allow IGMP  client joins?

A – On Central router : “ip pim neighbors filter” & the Stub router : “ip igmp helper-address”

2. Q – Filter specific multicast groups, while still allowing IGMP traffic?

A – “ip multicast boundary {acl}”

3. Q – Deny clients from joining specific multicast groups?

A – “ip igmp access-group {acl}”

4. Q – Statically filter RP requests and responses, (no Auto-RP, no BSR)?

A – “ip pim rp address {IP} {acl}”

5. Q – Client RP filtering, Limit join/prune messages for specific RP’s?

A – “ip pim accept-rp {RP-IP/auto-RP} {acl}”

6. Q – Auto-RP – Limit the Candidate-RP’s announcements?

A – “ip pim send-rp-announce {int} scope {no} group-list {acl}”

7. Q – Auto-RP – Limit what mgroups a MA accept from specific RP’s?

A – “ip pim rp-announce-filter rp-list {acl} group-list {acl}”

8. Q – Filter the BSR messages on a interface?

A – “ip pim bsr-border”

9. Q – Limit the amount of multicast routes in the mrouting table?

A – “ip multicast route-limit”

10. Q – Limit the rate a source can sent traffic to a group on a interface?

A – “ip multicast rate-limit group-list {acl} {kbps}”


  • RIPng – “no ip split-horizon” in a process command not a interface command.
  • EIGRPv6 – Do not forget to enable eigrp under the process.
  • IPv6 tunnel method with least overhead : IPv6IP
  • Tunnel protocol numbers for ACL’s : IPv6IP = Protocol-41,  &  GRE IPv6 = Protocol-47
  • You can not redistribute a default static route(::/0) with ospfv3.
  • Dynamic information (ie IGP next-hops)  recurses to remote link-local address, not the global unicast interface.

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