PurposeCommand or Action
•
The level-2-only keyword configures the software to perform
Level 2 (backbone) routing only, and the router establishes only
Level 2 adjacencies, either with other Level 2-only routers or
with level-1-2 routers.
•
The level-1-2 keyword configures the software to perform both
Level 1 and Level 2 routing. Both Level 1 and Level 2
adjacencies are established. The router acts as a border router
between the Level 2 backbone and its Level 1 area.
commit
Step 5
(Optional) Displays summary information about the IS-IS instance.
show isis [ instance instance-id ] protocol
Example:
RP/0/RSP0/CPU0:router# show isis protocol
Step 6
Configuring Single Topology for IS-IS
After an IS-IS instance is enabled, it must be configured to compute routes for a specific network topology.
This task explains how to configure the operation of the IS-IS protocol on an interface for an IPv4 or IPv6
topology.
Before You Begin
To enable the router to run in single-topology mode, configure each of the IS-IS interfaces with all of the
address families enabled and “single-topology” in the address-family IPv6 unicast in the IS-IS router
stanza. You can use either the IPv6 address family or both IPv4 and IPv6 address families, but your
configuration must represent the set of all active address families on the router. Additionally, explicitly
enable single-topology operation by configuring it in the IPv6 router address family submode.
Two exceptions to these instructions exist:
Note
1
If the address-family stanza in the IS-IS process contains the adjacency-check disable command,
then an interface is not required to have the address family enabled.
2
The single-topology command is not valid in the ipv4 address-family submode.
The default metric style for single topology is narrow metrics. However, you can use either wide metrics
or narrow metrics. How to configure them depends on how single topology is configured. If both IPv4
and IPv6 are enabled and single topology is configured, the metric style is configured in the address-family
ipv4 stanza. You may configure the metric style in the address-family ipv6 stanza, but it is ignored in
this case. If only IPv6 is enabled and single topology is configured, then the metric style is configured in
the address-family ipv6 stanza.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
OL-30423-03 287
Implementing IS-IS
Configuring Single Topology for IS-IS
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