User guide
Configuring IS-IS Configuring IS-IS
page 3-18 OmniSwitch AOS Release 7 Advanced Routing Configuration Guide March 2015
When the level capabilities are configured both globally and on per-interface basis, the combination of the
two settings will decide the potential adjacency. The rules for deciding the potential adjacency is explained
in the following table:
• When the router is globally configured to act at both levels (Level-1/2) and the interface is configured
to act at any level, the potential adjacency will be the level adjacency of the interface.
• When the router is globally configured to act at Level-1, the potential adjacency will also be Level-1. If
the interface is configured at Level-2 capability, the router will not form potential adjacency with the
neighbor.
• When the router is globally configured to act at Level-2, the potential adjacency will also be at Level-2.
If the interface is configured at Level-1 capability, the router will not form potential adjacency with the
neighbor.
Enabling Summarization
Route summarization in IS-IS reduces the number of routes that a router must maintain, and represents a
series of network numbers in a single summary address.
Summarization can also be enabled or disabled when creating an area. IS-IS routes can be summarized
into Level-2 from the Level-1 database. It is not possible to summarize IS-IS internal routes at Level-1,
although it is possible to summarize external (redistributed) routes. You can summarize level-1, level-2,
level-1/2 IS-IS routes. The metric that is used to advertise the summary address is the smallest metric than
any of the more specific IP routes.
For example, to summarize the routes between 100.1.1.0/24 and 100.1.100.0/24 into one, enter the
following command:
-> ip isis summary-address 100.1.0.0/16 level-2
To remove the summary address, enter the following:
-> no ip isis summary-address 100.1.0.0/16 level-2
Global Level
Interface
Level
Potential
Adjacency
Level-1/2 Level-1 Level-1
Level-1/2 Level-2 Level-2
Level-1/2 Level-1/2 Level-1 and/or
Level-2
Level-1 Level-1 Level-1
Level-1 Level-1 None
Level-1 Level-1/2 Level-1
Level-2 Level-1 None
Level-2 Level-2 Level-2
Level-2 Level-1/2 Level-2