Cisco IP phone reboots upon loosing one of the WAN.

[r.boloor.rao]

We have our CUCM at Datacenter and Client is in remote Site. Central Site and Remote Site both connected via MPLS provider with DS3 circuits. On the remote site we have two DS3 links going to the Provider. Topology is as below.

Phone-->Switch1 -----Router1 --------ds3-------/--------------------\ ---------ds3----------DataCenter(Primary)

                         \-----Router2---------ds3---- -| MPLS            |

                                                               \-------------------- / ----------ds3---------DataCenter(Secondary)

What we are observing is when one of the ds3 goes down. the phone reboots and fails back to secondary. We have set the keep-alive as default 30 seconds on cisco call managers. The nework converges much before 30 seconds but somehow Phones dont keep up. I was expecting the phone would wait wait till 3 keep alives ie 3x30=90 seconds. but phone reboots much before..

we are using cucm 7.1.5

Any hint on this is much appreciated.

Thanks.

[Dennis Mink · Accepted solution]

Mate,

not sure if you have read this post:

https://supportforums.cisco.com/docs/DOC-19066

this post states:

By default, CUCM uses Normal failover behavior as set by the "Detect Unified CM Connection Failure" parameter on the device configuration page. The Normal setting was introduced as an enhancement in phone load 7.2(1) and is also known as Geometric TCP Phone Failover, or adaptive failover. Geometric Failover was introduced as an improvement to the previous default configuration (now refererred to under the same parameter as "Delayed") as it allows for a much faster conversion to the secondary CUCM node when the TCP connection to the primary CUCM fails to respond to the keepalives sent from the phone.

It looks you are misinterpreting the 30 seconds keepalive principle (3x missed keep alive is fail over), becuase if an ACK is not received on a keepalive, subsequent keepalive frequencies are adaptive.

please red the following release notes (as an example):

(http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/firmware/8_4_2/english/release/notes/79xx_842.html )

Geometric TCP

The Cisco Unified IP Phone firmware 7.2(1) introduced a Geometric TCP mechanism to permit IP Phones to measure the round-trip delay between the IP Phone and Unified CM, then adapt the keepalive timeout value. This provided a very accurate failover mechanism when the network delay is consistent.

However, if the network delay is inconsistent, this mechanism may cause the IP Phones to inaccurately attempt failover. The Cisco Unified IP Phone firmware 8.4(2) introduces the ability for the Network Administrator to disable this behavior, if necessary, through the Detect Unified CM Connection Failure parameter defined on the IP Phone device configuration. The default value is Normal; this Geometric TCP mechanism can be disabled if the parameter is set to Delayed.

Would be worth checking your settings, as this could explain what you are seeing.

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