Local mode – Nortel Networks SRG50 User Manual
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Chapter 2 SRG50 overview
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SRG50 Configuration Guide
Local mode
In the event of a WAN failure or the call server at the main office becomes unavailable, the
IP Phones in normal mode revert to local mode automatically. In local mode, the IP users
connected to the SRG are under the control of the SRG. When in local mode, main office call
features are not available to users attached to the SRG. The SRG offers a set of basic features for
the IP telephones, including access to the local PSTN, dialing emergency service numbers, and
calling local extensions. For a complete list of local mode features, see
page 62. Local mode is illustrated in the figure
Figure 2 Local mode
The SRG handles all call processing. Calls between two IP telephones at the SRG are handled
locally as a simple station-to-station call. When an IP telephone initiates a local PSTN call, the
SRG routes the call to a trunk that is connected to the local PSTN. Incoming DID calls are also
handled by the SRG and terminated on the appropriate IP telephone set.
In local mode, the IP telephones do not have access to the main office network over the VoIP
trunks. If alternate routes are configured, then calls can be made to the main office or other branch
offices using the available PSTN trunks.
Several situations, described below, can cause the IP phone to be in local mode.
Initial registration
When the IP telephone is installed, it first registers with the SRG, and is in local mode. When the
SRG configuration at the main office and the SRG is complete the IP telephone is redirected to the
main office, where it registers as a branch user and changes from local mode to normal mode.
Note: The IP Phone KEM is supported on an SRG with normal mode IP Phones.
It does not function with local mode or test local mode IP Phones.
Branch office
Main office
WAN connectivity lost,
IP phones
IP phones
Local mode
SRG
Software
phones
WLAN
handsets
PSTN provides fallback
polling
SRG