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Configuring Passive Interfaces
passive-interface
Copyright © 2010, Juniper Networks, Inc.
Priorities are used to determine which router in the network is the designated
intermediate system (DIS); the router with the highest priority becomes the DIS.
Priorities are advertised in hellos.
IS-IS has no backup designated router. Setting the priority to 0 reduces the chance of
this router becoming the DIS, but does not prevent it. If a router with a higher priority
is identified, it takes over the role from the current DIS. When priorities are equal, the
highest MAC address breaks the tie and becomes the DIS.
Example
host1(config-if)#isis priority 80 level-1
Use the no version to restore the default value, 64.
See isis priority
You can configure an IS-IS passive interface. A passive interface only advertises its IP
address in its LSPs; it does not send or receive IS-IS packets.
Optionally, you can set a route tag for an IS-IS passive interface by including the tag
keyword and a numeric tag value in the passive-interface command.
Passive interfaces have a metric of zero by default. You can set a different metric for a
particular passive interface by specifying the value along with the metric keyword. A
global default metric set with the metric command does not affect any passive interface.
Similarly, configuring a reference bandwidth for IS-IS has no effect on passive interfaces.
Metrics specified for a passive interface apply to both level 1 and level 2 interfaces unless
you restrict the metric to a single level.
Use to configure an IS-IS interface so that its IP address is advertised in its link-state
PDUs but no IS-IS packets are sent from or received on the interface.
Use the optional tag keyword to specify a tag value for an IS-IS passive interface before
the route is propagated to other routers in an IS-IS domain. The tag value must be a
number in the range 1–4294967295.
Use the optional metric keyword to specify a metric value for an IS-IS passive interface.
The metric value must be a number in the range 1–16777215. This value overrides the
default metric of zero.
You can also accomplish the equivalent of the passive-interface command by using
the redistribute command to redistribute a connected route to level 1.
Example 1—Configures loopback 0 as a passive interface and enable IS-IS on
subinterfaces ATM 2/0.1 and ATM 2/1.1. IS-IS advertises the IP address of loopback 0
in its link-state PDUs, but runs only on ATM 2/0.1 and ATM 2/1.1:
host1(config)#router isis floor12
host1(config-router)#net 47.0010.0000.0000.0000.0001.0001.1111.1111.1111.00
host1(config-router)#passive-interface loopback 0
host1(config-router)#exit
Chapter 6: Configuring IS-IS
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