Tuning and Optimizing IS-IS Network 347
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If multiple routers in the broadcast network have the same highest DIS priority, the
router with the highest MAC address becomes the DIS. This rule applies even all
routers’ DIS priority is 0.
Configuring IS-IS Timers Follow these steps to configure the IS-IS timers:
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■ On the broadcast link, you can specify different intervals for Level-1 and Level-2
hello packets; if no level is specified, the interval applies to both Level-1 and
Level-2 hello packets, but only takes effect on the level of the current process;
if a level is specified, it applies to hello packets at this level. The point-to-point
link does not distinguish between Level-1 and Level-2 hello packets, so you
need not specify a level.
■ Hello packets are used to establish and maintain neighbor relationships. If no
hello packets are received from a neighbor within the time for receiving the
specified hello packets, the neighbor is considered dead.
■ CSNPs are sent by the DIS on a broadcast network for LSDB synchronization. If
no level is included, the specified CSNP interval applies to both Level-1 and
Level-2 of the current IS-IS process. If a level is specified, it applies to the level.
■ On a point-to-point link, if there is no response to a LSP sent by the local router
within the specified retransmission interval, the LSP is considered lost, and the
same LSP will be retransmitted. On broadcast links, responses to the sent LSPs
are not required.
■ The interval between hello packets sent by the DIS is 1/3 the hello interval set
by the isis timer hello command.
Disabling an Interface
from Sending/Receiving
IS-IS Hello Packets
Follow these steps to disable an interface from sending hello packets:
To do… Use the command… Remarks
Enter system view system-view --
Enter interface view interface interface-type
interface-number
--
Specify the interval between
hello packets
isis timer hello seconds
[ level-1 | level-2 ]
Optional
10 seconds by default
Specify the number of hello
packets; within the time for
receiving the specified hello
packets, if no hello packets
are received on the interface,
the neighbor is considered
dead.
isis timer
holding-multiplier value
[ level-1 | level-2 ]
Optional
3 by default
Specify the interval for
sending CSNP packets
isis timer csnp seconds
[ level-1 | level-2 ]
Optional
10 seconds by default
Specify the interval for
sending LSP packets
isis timer lsp time [ count
count ]
Optional
33 milliseconds by default
Specify the LSP retransmission
interval on the point-to-point
link
isis timer retransmit
seconds
Optional
5 seconds by default
To do… Use the command… Remarks
Enter system view system-view --
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