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Phone issue with CUCM 8 and CUCM 6


we are installing a new setup which includes CUCM 8 and with IPCC setup. We already have DHCP Pool configured on one of the Core swich for existing Production, this includes option 150 pointing to old CUCM setup. We were setting up POC and in regards to this we created a another DHCP pool with 30 IP address to be leased, this included a option 150 pointing to new CUCM. I had some access switch ports on different VLAN which points to the new dhcp pool. The problem is when i connect the Phone to new subnet, it behaves good. when i reconnect the Phones to old Subnet, the Phone takes IP address from he production subnet, but the tftp isnt getting updated. Even if it gets updated the CUCM Server1 and 2 dont get updated with old Server IP address. It still shows new IPs. a factory reset is resolving this? Any idea y this happens


Phone issue with CUCM 8 and CUCM 6


IP Phone do not release CUCM ip address easily. Factory reset, or erase configuration may help you.

Or follow folloing link for other workarounds.


Ronak patel

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Regards Ronak Patel Rate all helpful post by clicking stars below the answer.
Super Bronze

Phone issue with CUCM 8 and CUCM 6


Your problem is that the phones are obtaining an ITL (Trust List) from the CUCM8.0 cluster. Once they have this they will not download config from a different cluster until that list is cleared or unless that ITL contains a reference to the other cluster.

The easiest way to deal with this in a lab scenario is to turn on the 'prepare cluster for pre 8.0 rollback' enterprise parameter on the 8.0 cluster. This tells the cluster to send out a blank ITL, which means that the phones should trust any cluster TFTP.


Aaron Harrison

Principal Engineer at Logicalis UK

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Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!