Configuring Link-State Metrics; Configuring A Reference Bandwidth To Set A Default Metric - Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual

Configuring Link-State Metrics

You can configure the routing metric (cost) for an IS-IS interface. Routes with lower
total path metrics are preferred over those with higher path metrics.
isis metric

Configuring a Reference Bandwidth to Set a Default Metric

By default, all IS-IS interfaces without a configured metric have the same routing
metric, 10, However, when you configure a reference bandwidth for IS-IS, the default
metric is calculated differently for each IS-IS interface. The default routing metric in
this case is the reference bandwidth divided by the bandwidth of the particular
interface.
Example
host1(config-if)#isis message-digest-key 3 hmac-md5 wdi6c3s39n level-2
For point-to-point interfaces, configure keys only for level 1, because only one
hello packet is sent (at level 1), not one at level 1 and one at level 2. Keys
configured at level 2 are ignored for point-to-point interfaces.
Use the no version to delete the MD5 key, specified by the key ID, from the
interface.
See isis message-digest-key
Use to configure a cost for a specified interface.
You can select a number in the range 0–63 if you configured the router with the
metric-style narrow command. You can select a number in the range
0–16277215 if you configured the router with the metric-style transition or the
metric-style wide command.
The default value is 10. The default metric is the value assigned when no quality
of service (QoS) routing is performed.
You can configure the default metric for a specified interface by selecting level
1 or level 2 routing. This resets the metric only for level 1 or level 2 routing,
respectively. If you do not specify a level, the command specifies both level 1
and level 2 by default.
We recommend that you configure a reference bandwidth if you want the default
cost on interfaces to be related to link speed. If you do not, the default IS-IS
metrics are simply hop-count-like metrics.
Example
host1(config-if)#isis metric 20 level-2
Use the no version to restore the default value, 10.
See isis metric
Configuring IS-IS Interface-Specific Parameters
Chapter 6: Configuring IS-IS
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