Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 278)

250 Multi-Service IronWare Routing Configuration Guide
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Relationship to IP route table
Figure 17 shows an example of an IS-IS network.
FIGURE 17 An IS-IS network contains Intermediate Systems (ISs) and host systems
NOTE
Since the implementation of IS-IS does not route OSI traffic but instead routes IP traffic, IP hosts are
shown instead of ESs.
The other basic IS-IS concepts illustrated in this figure are explained in the following sections.
Domain and areas
IS-IS is an IGP, and thus applies only to routes within a single routing domain. However, you can
configure multiple areas within a domain. A Brocade device can be a member of one area for each
Network Entity Title (NET) you configure on the Brocade device. The NET contains the area ID for
the area the NET is in.
In Figure 17 , Routers A, B, and C are in area 1. Routers D and E are in area 2. All the routers are in
the same domain.
Level-1 routing and Level-2 routing
You can configure an IS-IS router such as a Brocade device to perform one or both of the following
levels of IS-IS routing:
NOTE
The ISO/IEC specifications use the spelling “routing”, but this document uses the spelling “routing”
to remain consistent with other Brocade documentation.
• Level-1 – A Level-1 router routes traffic only within the area the router is in. To forward traffic to
another area, the Level-1 router sends the traffic to its nearest Level-2 router.