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Community Member

Multicast routing issues when a subinterface is configured

Strange issue here. Cisco and the vendor are unable to help so far...

Most of our layer 3 lives on core switches. However, we have  a couple sites off our WAN connected via  Cisco routers. In these offices, we can not get paging to work.

I  setup a lab and have finally determined what is at least causing the  issue. My lab "branch" has  the same problems, but I can resolve the  problem by removing the sub-interface off the router.

On my LAN side  of the router, with this  config, everything works fine.

#--- THIS WORKS ---#

R1#
ip pim rp-address 192.168.251.254
!
gig 0/0 (connects to SW1 g0/1)
 ip address 10.254.253.254 255.255.255.0
 ip pim sparse-dense mode

SW1#
 gig 0/1 (connects to R1 g0/0)
 !no config - default VLAN1
--------------------

When I apply this config...everything breaks. The phone goes off

#--- THIS DOES NOT WORK ---#
R1#
ip pim rp-address 192.168.251.254
!
gig 0/0 (connects to SW1 g0/1)
 no ip
gig 0/0.777 (connects to SW1 g0/1)
 ip address 10.254.253.254 255.255.255.0
 ip pim sparse-dense mode


SW1#
 gig 0/1 (connects to R1 g0/0)
 sw mode trunk
 sw trunk  encap dot1q
!
int vlan 777
 ip address 10.254.253.1 255.255.255.0
 ip pim sparse-dense mode
!
int vlan 778
 ip address 10.254.251.1 255.255.255.0
 ip pim sparse-dense mode
!
 gig 0/17 (phone port)
 switch access vlan 778 (keeping it simple for now)
----------------------------

 

I have tried this on 2 different model routers, each with different IOS versions.  The same issues follow each router. What is it about the  sub interfaces?

Any insight? Calling all multicast experts! Thanks!

Everyone's tags (1)
3 REPLIES
Cisco Employee

Hi,creating sub-interface

Hi,

creating sub-interface should not create any difference here. Only difference i can see earlier switch was working in l2 mode now it is participating in multicast routing as SVI is configured and pim neighborship established. Have you configured RP address on SW1. Please share below outputs from both devices

 

- running config

- show ip mroute <group>

- show ip pim rp address mapping

 

Regards,

Akash

Community Member

On the router R1, try to add

On the router R1, try to add the following command :

gigabit0/0.777
 encapsulation dot1q
 

Community Member

Thanks Akash, I thought you

Thanks Akash, I thought you were on to something there. However, I configured the RP address on SW1 and the results were the same. The phone goes off hook,but no audio.

I will  work on getting you the results from the commands you want. I will provide them when paging is working and when paging is not working. Give me a bit...

Mat

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