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New Member

Phone Behind 831 No Register w/ CM

Interesting situation.

I have a 7940 IP Phone behind a 831 Router. This phone obtains DHCP from a centralized server just fine. It then obtains, via TFTP, it's config file, but it will not register with the primary Subscriber CM. It will only register with the secondary Publisher CM.


The phone is on a private 10.x.x.x network, the CallManagers are on a 129.9.x.x network.

If I change the config on the 831 router and place the phone on it's own 129.9.x.x subnet behind the router, it works just fine.

The problem only occurs if all three are true:

1) The phone is on a non 129.9.x.x network

2) The phone is sending TCP packets (UDP works fine)

3) The phone is behind a 831 router

If any of those are not true, the phone registers just fine.

Please note that when the phone does not register, it keeps "retransmitting" the packet. SYN.. SYN.. SYN.. the CallManager keeps sending back ACK's but the phone never sees them.

New Member

Re: Phone Behind 831 No Register w/ CM

I have stripped down the config on the 831 router. Here it is. Very basic.

service config

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption


hostname Router


enable secret xxxx.

enable password xxxx


username all

ip subnet-zero

ip dhcp excluded-address

ip dhcp excluded-address


ip dhcp pool CLIENT

import all




netbios-node-type h-node

domain-name heidrick.hsi

option 150 ip


option 160 ip

lease 0 2


ip audit notify log

ip audit po max-events 100





interface Ethernet0

ip address

hold-queue 100 out


interface Ethernet1

ip address


ip classless

ip route

ip http server



access-list 11 permit

access-list 100 deny ip any host


line con 0

exec-timeout 120 0

no modem enable

stopbits 1

line aux 0

stopbits 1

line vty 0 4

exec-timeout 120 0

password xxx

no login

length 0


scheduler max-task-time 5000



Re: Phone Behind 831 No Register w/ CM


Are you able to ping from CM 1 to the phone?

what shows a traceroute?

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