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Madhan Kumar

Some Cisco IP phones are not getting registered if I down the Core - 1

Hi Experts,

I am  working in Private IT company. The facility is having 4000 users and it is a high resliency site having two core switches and nearly 40 access switches. All core and access switches are 4506E switches and odd vlan is taking core-1 and even vlan is core-2. We are having cisco ip phones 6921 connected as daisy chain.( Phone is connected to access switch and the desktop is connected to ip phones). The Ip phone are getting registered cisco call maneger server. The call manager one leg is connected to one core switch and another one is core 2 same like my DHCP server.

For all vlans the the default gateway is my firwall. The voice needs to hit the call manager, hence we have implemented a source routing to call manager for the voice vlans.

Herer the problem is once we down the Core-1 some of the IP phones are not getting registered no matterit is on odd or even vlan. The same issue for Core-2. We suspect that there might be some issue in the DHCP server for voice vlan routing. But server team is saying that there is no issue with the DHCP server.

Now network is vulnerable that if any core switch is down my voice ip phones will be down.

If any help will really appreciate.

Thanks & Regards



If you reset the phone, does it associate correctly?

I dont understand your topology, does your core do routing or do your firewall have interfaces in all vlans?


No. After manual reset also the phones are not getting registered. If I manualy give static ip to phone it is getting registered with call manger.

For voice vlans the routing happens in core switche, for data vlans the routing on my firewall sub interface.

Thanks & Regards


Where are the DHCP server located? Are the ip helper configured on the two core switches?