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Cisco ASR 901 Aggregation Services Router Command Reference Guide
OL-26031-07
Chapter 1 CLI Command Reference
router isis
Explicit redistribution between IS-IS instances is prohibited (prevented by the parser). In other words,
you cannot issue a
redistribute isis
area-tag
command in the context of another IS-IS router instance
(
router isis
area-tag
). Redistribution from any other routing protocol into a particular area is possible,
and is configured per router instance, as in Cisco IOS software Release 12.0, using the
redistribute
and
route map
commands. By default, redistribution is into Level 2.
If multiple Level 1 areas are defined, the Target Address Resolution Protocol (TARP) behaves in the
following way:
•
The locally assigned target identifier gets the network service access point (NSAP) of the Level 2
area, if present.
•
If only Level 1 areas are configured, the router uses the NSAP of the first active Level 1 area as
shown in the configuration at the time of TARP configuration (“tarp run”). (Level 1 areas are sorted
alphanumerically by tag name, with capital letters coming before lowercase letters. For example,
AREA-1 precedes AREA-2, which precedes area-1.) Note that the target identifier NSAP could
change following a reload if a new Level 1 area is added to the configuration after TARP is running.
•
The router continues to process all Type 1 and 2 protocol data units (PDUs) that are for this router.
Type 1 PDUs are processed locally if the specified target identifier is in the local target identifier
cache. If not, they are “propagated” (routed) to all interfaces in the
same
Level 1 area. (The same
area is defined as the area configured on the input interface.)
•
Type 2 PDUs are processed locally if the specified target identifier is in the local target identifier
cache. If not, they are propagated via all interfaces (all Level 1 or Level 2 areas) with TARP enabled.
If the source of the PDU is from a different area, the information is also added to the local target
identifier cache. Type 2 PDUs are propagated via all static adjacencies.
•
Type 4 PDUs (for changes originated locally) are propagated to all Level 1 and Level 2 areas
(because internally they are treated as “Level 1-2”).
•
Type 3 and 5 PDUs continue to be routed.
•
Type 1 PDUs are propagated only via Level 1 static adjacencies if the static NSAP is in one of the
Level 1 areas in this router.
After you enter the
router isis
command, you can enter the maximum number of paths. There can be
from 1 to 32 paths.
Examples
The following example starts IS-IS routing with the optional
area-tag
argument, where CISCO
is the
value for the
area-tag
argument:
router isis CISCO
The following example specifies IS-IS as an IP routing protocol for a process named Finance, and
specifies that the Finance process will be routed on Ethernet interface 0 and serial interface 0:
router isis Finance
net 49.0001.aaaa.aaaa.aaaa.00
interface Ethernet 0
ip router isis Finance
interface serial 0
ip router isis Finance
The following example shows usage of the
maximum-paths
option:
router isis
maximum-paths?
20
