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ACI LEAF skips to register mrouter port when it received PIM Hello from multicast router. As a result, multicast switching on ACI doesn't happen as expected due to lack of a mrouter port.
This issue happens when IGMP Snooping process on ACI LEAF recognizes PIM is enabled on BD by mistake even though PIM is disabled on BD config on APIC. This misunderstanding on LEAF occurs when the following steps are performed. 1. Enable both Unicast Routing and PIM on BD. (multicast doesn't have to be enabled on VRF to hit this issue) 2. Disable Unicast Routing while PIM is still enabled. (at this point, F2305 will be raised as Unicast Routing needs to be enabled for PIM) 3. Then, disable PIM After these three steps, PIM is disabled on BD from APIC perspective but IGMP Snooping process on LEAF still thinks it's enabled by mistake and it skips mrouter port registration event on this BD.
To resolve this issue, follow this three steps to make IGMP Snooping process on LEAF correctly recognize PIM is disabled. 1. Enable both Unicast Routing and PIM on BD again 2. Disable PIM first 3. Then finally disable Unicast Routing
Following is an example of command output and logs when it's NOT working and IS working. //////////////////////////////// WHEN IT IS NOT WORKING //////////////////////////////// admin@apic1:~> moquery -d uni/tn-TK/BD-BD1 | egrep '#|mcast|unicast' # fv.BD mcastAllow : no <--- PIM is disabled on APIC unicastRoute : no <--- Unicast Routing is disabled on APIC fab5-leaf1# moquery -d sys/igmpsnoop/inst/dom-[vxlan-15826915] | egrep '#|ctrl|id|name' # igmpsnoop.Dom ctrl : routing <--- multicast routing is enabled even though PIM is disabled on APIC !!!!! id : 15 <--- BD PI-VLAN name : TK:BD1 fab5-leaf1# vsh -c 'show ip igmp snooping vlan 15' Warning: could not get list of reserved vlans IGMP Snooping information for BD 15 IGMP snooping enabled Lookup mode: IP Optimised Multicast Flood (OMF) enabled IGMP querier none Switch-querier disabled IGMPv3 Explicit tracking enabled IGMPv2 Fast leave disabled IGMPv1/v2 Report suppression enabled IGMPv3 Report suppression enabled Link Local Groups suppression enabled Router port detection using PIM Hellos, IGMP Queries Number of router-ports: 0 Number of groups: 0 VLAN vPC function enabled Routing enabled on VLAN <---- IGMP SN thinks Multicast Routing is enabled even though PIM is disabled on APIC !!!!! Active ports: Eth1/1 Eth1/2 fab5-leaf1# show ip igmp snooping event-history vlan | grep -B 2 PIM | head 2017 Jun 30 22:59:39.410774 igmp [9256]: TID 11021:igmp_snoop_process_mrd_update:9506: SN: Routing enabled on BD, skipping querier/mrouter on Eth1/1 <--- mrouter registration is skipped !!!! 2017 Jun 30 22:59:39.410659 igmp [9256]: TID 11021:igmp_snoop_process_mrd_update:9331: SN: Rcvd MRD from on intf Eth1/1, src_mac:0000.5555.1111 2017 Jun 30 22:59:39.410651 igmp [9256]: TID 11021:igmp_snoop_process_mrd_update:9306: SN: IGMPSN: Received a PIM Hello with Encap VID:16 BD VID:15 from (Eth1/1) fab5-leaf1# show ip igmp snooping groups vlan 15 Type: S - Static, D - Dynamic, R - Router port, F - Fabricpath core port Vlan Group Address Ver Type Port list <------ no router port !!!! //////////////////////////////// WHEN IT IS WORKING //////////////////////////////// admin@apic1:~> moquery -d uni/tn-TK/BD-BD1 | egrep '#|mcast|unicast' # fv.BD mcastAllow : no <--- PIM is disabled on APIC unicastRoute : no <--- Unicast Routing is disabled on APIC fab5-leaf1# moquery -d sys/igmpsnoop/inst/dom-[vxlan-15826915] | egrep '#|ctrl|id|name' # igmpsnoop.Dom ctrl : <--- multicast routing is disabled id : 15 <--- BD PI-VLAN name : TK:BD1 fab5-leaf1# vsh -c 'show ip igmp snooping vlan 15' Warning: could not get list of reserved vlans IGMP Snooping information for BD 15 IGMP snooping enabled Lookup mode: IP Optimised Multicast Flood (OMF) enabled IGMP querier present, address: 192.168.0.51, version: 2, i/f Eth1/1 Switch-querier disabled IGMPv3 Explicit tracking enabled IGMPv2 Fast leave disabled IGMPv1/v2 Report suppression enabled IGMPv3 Report suppression enabled Link Local Groups suppression enabled Router port detection using PIM Hellos, IGMP Queries Number of router-ports: 1 Number of groups: 0 VLAN vPC function enabled Routing disabled on VLAN <---- Multicast Routing is disabled Active ports: Eth1/1 Eth1/2 fab5-leaf1# show ip igmp snooping event-history vlan | grep -B 2 PIM | head 2017 Jun 30 23:02:32.350251 igmp [9256]: TID 11021:igmp_snoop_update_router_port:43: SN: Received update with encap_vlan:16 2017 Jun 30 23:02:32.350133 igmp [9256]: TID 11021:igmp_snoop_process_mrd_update:9331: SN: Rcvd MRD from on intf Eth1/1, src_mac:0000.5555.1111 2017 Jun 30 23:02:32.350125 igmp [9256]: TID 11021:igmp_snoop_process_mrd_update:9306: SN: IGMPSN: Received a PIM Hello with Encap VID:16 BD VID:15 from (Eth1/1) fab5-leaf1# show ip igmp snooping groups vlan 15 Type: S - Static, D - Dynamic, R - Router port, F - Fabricpath core port Vlan Group Address Ver Type Port list 15 */* - R Eth1/1 Vlan15 <---- mrouter port is registered