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ATM Switch Router Software Configuration Guide
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Chapter7 Configuring Virtual Connections
Configuring Soft PVCs with Explicit Paths
Configuring Soft PVCs with Explicit Paths
Normally, softPVCs and soft PVPs are automatically routed by PNNI over paths that meet the traffic
parameter objectives. However, for cases where manually configured paths are needed, PNNI explicit
paths can optionally be specified for routing the softPVC or soft PVP. For detailed information on
configuring PNNI explicit paths, see Chapter1 1, “Configuring ATM Routing and PNNI.”
The explicit paths are assigned using precedence numbers 1 through 3. The precedence 1 path is tried
first and if it fails the soft connection is routed using the precedence2 path and so forth. If all of the
explicit paths fail, standard on-demand PNNI routing is tried unless the only-explicit keyword is
specified.
If the soft connection destination address is reachable at one of the included entries in an explicit path,
any following entries in that path are automatically disregarded. This allows longer paths to be reused
for closer destinations. Alternatively, the upto keyword can be specified for an explicit path in order to
disregard later path entries.
Example
The following example shows how to configure a soft PVC between ATM switch router dallas_1 and an
address on ATM switch router new_york_3 using either of the two explicit paths new_york.path1 and
new_york.path2. If both explicit paths fail, the ATM switch router uses PNNI on-demand routing to
calculate the route.
dallas_1(config)# interface atm 0/0/0
dallas_1(config)# atm soft-vc 0 201 dest-address
47.0091.8100.0000.1061.3e7b.2f99.4000.0c80.0030.00 0 101 explicit-path 1 name
new_york.path1 explicit-path 2 name new_york.path2

Changing Explicit Paths for an Existing Soft PVC

Explicit paths can be added, modified or removed without tearing down existing soft PVCs by using the
redo-explicit keyword. Only the source VPI and VCI options need to be specified. All applica ble
explicit path options are replaced by the respecified explicit path options.
The soft PVC is not immediately rerouted using the new explicit path. However, reroutes using the new
explicit path can happen for the following four reasons:
1. A failure occurs along the current path.
2. The EXEC command atm route-optimization soft-connection is entered for the soft PVC.
3. route-optimization is enabled and the retry time interval has expired.
4. The soft PVC is disabled and then reenabled using the disable and enable keywords.
Example
The following example shows how to change the explicit path configuration for an existing soft PVC on
the ATM switch router dallas_1 without tearing down the connection. The new configuration spec ifies
the two explicit paths, new_york.path3 and new_york.path4, and uses the only-explicit option.
dallas_1(config)# interface atm 0/0/0
dallas_1(config)# atm soft-vc 0 201 redo-explicit explicit-path 1 name new_york.path3
explicit-path 2 name new_york.path4 only-explicit