Specifications

Chapter 8 Configuring Survivable Remote Site Telephony
Overview of Survivable Remote Site Telephony
8-6
Catalyst 4224 Access Gateway Switch Software Configuration Guide
OL-2031-02
Cisco IP Phones periodically attempt to reestablish connections with the remote
Cisco CallManagers. When a connection is reestablished with a remote
Cisco CallManager, the Cisco IP Phones unregister from the local Catalyst 4224
with the SRST feature and register with the remote Cisco CallManager. The
connection to the primary Cisco CallManager at the remote office cannot be
reestablished if the telephone has active calls.
Figure 8-1 shows a branch office with several Cisco IP Phones connected to a
Catalyst 4224. The Catalyst 4224 is connected to the remote centralized
Cisco CallManager by the WAN and PSTN.
Figure 8-1 Branch Office Cisco IP Phones Connected to the Remote Central Cisco CallManager
Figure 8-2 shows that the WAN connection to the branch office is down and that
the Cisco IP Phones are able to make calls by being connected to the local SRST
Catalyst 4224. This Catalyst 4224 acts as a fallback Cisco CallManager. The
branch office Cisco IP Phones on the LAN network, connected to the PSTN, are
capable of making off-net calls outside the network using the Catalyst 4224s.
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Catalyst 4224
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Telephone Telephone
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