Dear Francisco Valle

The time taken to reestablish connection to a remote Cisco CallManager depends in part on the keepalive period set by Cisco CallManager itself. Typically, three times the keepalive period is required for a phone to discover that its connection to Cisco CallManager has failed. The default keepalive period is 30 seconds. If the phone has an active standby connection established with an SRS Telephony router, the fallback process takes 10 to 20 seconds after connection with Cisco CallManager is lost. An active standby connection to an SRS Telephony router exists only if the phone has the location of a single Cisco CallManager in its CallManager list. Otherwise, the phone activates a standby connection to its secondary Cisco CallManager.

If a Cisco IP phone has multiple Cisco CallManagers in its CallManager list, it progresses through its list of secondary and tertiary Cisco CallManagers before attempting to connect with its local SRS Telephony router. Therefore, the time that passes before the Cisco IP phone eventually establishes a connection with the SRS Telephony router increases with each attempt to contact a Cisco CallManager. Assuming that each attempt to connect to Cisco CallManager takes around 1 minute, the Cisco IP phone in question could remain offline for 3 minutes or more following a WAN link failure.

<http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide_chapter09186a0080110b97.html#wp1322470>

hth

Ajaz