Version 7.0 513 Mediant 3000
User's Manual 25. Routing
25.6 Alternative Routing for Tel-to-IP Calls
The device supports various alternative Tel-to-IP call routing methods, as described in this
section.
25.6.1 Alternative Routing Based on IP Connectivity
You can configure the device to route Tel-to-IP calls to an alternative IP destination when
the connectivity state of an IP destination is unavailable. The alternative routing rules are
configured in the Tel-to-IP Routing table. These rules must be configured anywhere below
the "main" routing rule and with identical matching characteristics (e.g., destination prefix
number) to the "main" routing rule. The device uses the first alternative route that is
available. For more information on configuring alternative Tel-to-IP routing rules in the Tel-
to-IP Routing table, see ''Configuring Tel-to-IP Routing Rules'' on page 496.
Note: Alternative routing based on IP connectivity is applicable only when a proxy
server is not used.
The device searches for an alternative routing rule (IP destination) when any of the
following connectivity states are detected with the IP destination of the "main" routing rule:
No response received from a ping or from SIP OPTIONS messages. This depends on
the chosen method for checking IP connectivity.
Poor QoS according to the configured thresholds for packet loss and delay.
Unresolved DNS, if the configured IP destination is a domain name (or FQDN). If the
domain name is resolved into two IP addresses, the timeout for INVITE re-transmissions
can be configured using the HotSwapRtx parameter. For example, if the parameter is
configured to 3 and the device receives no response upon its initial INVITE message to the
first IP address, it attempts up to three times to route the call to the first IP address and if
unsuccessful, it attempts to re-route the call to the second resolved IP address.
The connectivity status of the IP destination is displayed in the 'Status' column of the Tel-
to-IP Routing table per routing rule. If it displays a status other than "ok", the device
considers the IP destination as unavailable and attempts to re-route the call to an
alternative destination. For more information on the IP connectivity methods and on
viewing IP connectivity status, see ''IP Destinations Connectivity Feature'' on page 511.
The table below shows an example of alternative routing where the device uses an
available alternative routing rule in the Tel-to-IP Routing table to re-route the initial Tel-to-IP
call.
Table 25-6: Alternative Routing based on IP Connectivity Example
Destination
Phone Prefix
IP Destination
IP Connectivity
Status
Rule Used?
Main Route
40 10.33.45.68 "No Connectivity" No
Alternative Route #1
40 10.33.45.70 "QoS Low" No
Alternative Route #2
40 10.33.45.72 "ok" Yes
The steps for configuring alternative Tel-to-IP routing based on IP connectivity are
summarized below.
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