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2 Clusters, One DHCP server

Helo Everyone,

I have a situation that I need some help on. I have a customer that for various reasons I won't go into here is migrating from the existing cluster to a new cluster but both clusters need to be up at the same time as the migration is phased over several weeks. The problem is that they can only use one DHCP sever. This DHCP server is handing out all the addresses and has the old cluster's tftp address as the primary and the new cluster's tftp addres as secondary. When the phones come up the try to register with the old cluster first, get a registration rejected message and never try to register with the new cluster. Is there a way to get the phones to try the new cluster after getting rejected by the old cluster?

For this customer bringing a second DHCP server up or getting all VLANed up and getting switches and/or various routers to hand out DHCP addresses is not an option.

All replies will be rated

Thanks in advance!


Re: 2 Clusters, One DHCP server

Just break the original DHCP scope into 2 different scopes or create a new scope.

EX: scope for old cluster, and scope for new cluster and assign appropriate TFTP address in option 150.

Another option is manually configuring TFTP address on the phones.

Re: 2 Clusters, One DHCP server

Thanks for the reply. If the customer creates 2 scopes I don't get how that would solve my problem. From what I understand of your suggestion a new phone introduced to the network would pull and IP address from either scope. Withouth VLANs in place how would I restrict the new phones to only get addresses from the new scope and existing phones to get an address from the old scope?

Re: 2 Clusters, One DHCP server

Even if you break the scope, the phones could accept an address from the wrong scope (because devices accept the first request they receive). So the phones could still register to the old cluster. Once you break the scopes, on the phone Layer 3 vlan (SVI interface), change the ip helper-address to send all DHCP requests to the new server.




and now that i re-read ur question again, vlaning is not an option...

Re: 2 Clusters, One DHCP server


Now that I look through the IP Phone menu options, there is a regular TFTP server and an Alternate TFTP server. I am not sure if you can edit this field and specify the new CLutser's publisher's ip address.

Let me know if that will work, once yout test it.


Re: 2 Clusters, One DHCP server

Thanks Shanky. The only thing I seem to be able to do with that field is specify Yes or No. The new TFTP server's address does show up on the onld phone when they pull an IP address now but only as TFTP server 2 at #41 under the network configuration page on the phone. It looks like I am stuck with doing static IPs for all the phones that need to get to the new cluster

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