Dial Plan Configuration for SRST Support in CUCM Network bulls Best Networking Training Institute in india

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This section describes the configuration to adjust the CUCM dial plan to work with Cisco
Unified SRST.
The CUCM dial plan has to be adjusted to ensure the reachability of remote-site phones by
their extensions even if the remote site runs in SRST mode. The parameter that enables this
adjustment is the CFUR destination setting, which has to be defined on every line of an
SRST enabled remote-site phone. This parameter was introduced in Cisco Unified Communication
Manager Release 4.2.
The CFUR feature forwards calls to unregistered (disconnected or logged out) directory
numbers for the defined destination. The destination might be the PSTN number of a phone
at a remote site or the voice mail for a user in a CUCM Extension Mobility setting.
SRST Dial Plan of CFUR and CSS 133
To ensure that the feature works even if a major WAN breakdown disconnects all the remote
sites, only voice gateways located at the main site should be used. This can be ensured by
selecting the correct Calling Search Space (CSS) for the CFUR destination.
CFUR causes routing loops whenever there is a single disconnected SRST phone in
which the remote location is not in SRST mode. Internal calls to that directory number
are forwarded to the CFUR (PSTN) destination and are received by the remote-site gateway
in normal mode. This gateway handles the call as usual, sending the signaling to its
CUCM subscriber. CUCM then again forwards the call to the PSTN, causing an inevitable
routing loop.
To limit the impact of these routing loops, Cisco introduced a CUCM service parameter
called Max Forward UnRegistered Hops to DN. When activated, this counter limits the
calls that are forwarded to one CFUR destination.