MCasting blocked from VLAN to ETH 3Com NBX

Unanswered Question
Mar 12th, 2008

I have a new Cisco 871 with this config:

ip subnet-zero

ip cef



no ip domain lookup

ip domain name

ip multicast-routing

no ip igmp snooping




interface FastEthernet0


interface FastEthernet1


interface FastEthernet2


interface FastEthernet3


interface FastEthernet4

ip address

ip igmp version 3

duplex auto

speed auto


interface Vlan1

ip address

ip igmp static-group *

ip igmp version 3


router rip

version 2



ip classless

ip route permanent


ip http server

ip http authentication local

ip http secure-server

ip http timeout-policy idle 60 life 86400 requests 10000


no cdp run

I am trying to get a POE switch (plugged into F0) and phone (plugged into POE switch) to talk back over the F4 port to our NBX Phone system. F0 is a member of VLAN1.

I get power on the phone, and with my PC plugged into the phone tether port, I get an IP and can ping, etc. The only thing not working is the phone picking up a registration from multicasting from our NBX.

Thing is -- I know its something being blocked on this new 871 VLAN/Multi/Broad/Unicasting because if I bypass it the phone works fine.

Since this is an smaller 871 - PIM, Sparse, Dense, etc. all are not available to me.

I was hoping to get this router in our remote office this evening but I cannot for the life of me figure out how to get the router to just pass on all multicasting.

Can anyone make any recommendations?


I have this problem too.
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Edison Ortiz Wed, 03/12/2008 - 14:24

F4 and F0 are on different subnets. In order to transport multicast packets between subnets, it must be routed.

You've already stated this router does not support PIM so you have 2 choices.

1) Have only one Vlan

2) Get a device that support multicast routing and enable it on both Vlans.





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