3Com VCX V7122 User Manual page 53

Alternative routing (using this table) is commonly implemented when there is no response to
an Invite message (after Invite retransmissions). The gateway then issues an internal 408
'No Response' implicit release reason. If this reason is included in the 'Reasons for
Alternative Routing' table, the gateway immediately initiates a call to the redundant
destination using the next matched entry in the 'Tel to IP Routing' table. Note that if a domain
name in this table is resolved to two IP addresses, the timeout for Invite retransmissions can
be reduced by using the parameter 'Number of RTX Before Hotswap'.
Note: If the alternative routing destination is the gateway itself, the call can be configured to be
routed back to PSTN. This feature is referred to as "PSTN Fallback", meaning that if
sufficient voice quality is not available over the IP network, the call is routed through
legacy telephony system (PSTN).
Tel to IP routing can be performed either before or after applying the number
manipulation rules. To control when number manipulation is done, set the
RouteModeTel2IP parameter. For information on this parameter, see
page 119.
To configure the Tel to IP Routing table, follow these steps:
1 Open the 'Tel to IP Routing' screen (Protocol Management menu > Routing Tables
submenu > Tel to IP Routing option); the 'Tel to IP Routing' screen is displayed (shown
in Figure 20).
2 In the 'Tel to IP Routing Mode' field, select the Tel to IP routing mode (see
page 119).
3
In the 'Routing Index' drop-down list, select the range of entries that you want to edit.
4 Configure the Tel to IP Routing table according to
5 Click the Submit button to save your changes.
6
To save the changes so they are available after a power fail see
page 88.
Figure 20 Tel to IP Routing Table Screen
3Com VCX V7122 SIP VoIP Gateway User Manual
Table 17.
Save Configuration
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