Juniper IGP - CONFIGURATION GUIDE V11.1.X, Руководство по настройке

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Use the isis hello-interval command to set the length of time (in seconds)
between hello packets sent on a specific interface. Configure independently for
level 1 and level 2, except on point-to-point interfaces because only a single type
of hello packet is sent on serial links. For this reason, it is independent of levels
1 and 2. For example, you can specify an optional level for Frame Relay
multiaccess networks.
The hello-interval is equal to the hello multiplier times the hello interval seconds
and is advertised as the holdtime in the hello packets transmitted. The range is
0–65535; the default value is 10 seconds.
NOTE: The hello-interval value must be the same for all routers attached to a common
network. With smaller hello intervals, topological changes are detected faster, but
there is more routing traffic.
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Use the isis hello-multiplier command to set a number by which to multiply
the hello interval seconds. This number determines the total holding time
transmitted in the IS-IS hello packet. The default is 3. Use when hello packets
are frequently lost and IS-IS adjacencies are failing unnecessarily.
The advertised hold time in IS-IS hellos is set to the hello-multiplier times the
hello-interval. Neighbors declare an adjacency to this router to be down after
not having received any IS-IS hellos during the advertised hold time.
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The hold time (and thus the hello-multiplier and the hello-interval) can be
set on a per interface basis, and can be different between different routers
in one area.
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Using a smaller hello-multiplier will give fast convergence, but can result in
more routing instability.
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Increment the hello-multiplier to a larger value to help network stability
when needed.
CAUTION: Never configure a hello-multiplier lower than the default.
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Holding time—Time a neighbor waits for another hello packet before declaring
the neighbor is down. It determines how quickly a failed link or neighbor is
identified so that routes can be recalculated.
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Raise the hello multiplier and lower the hello interval simultaneously to make
the hello protocol more reliable without increasing the time required to detect
a link failure.
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Example
host1(config-if)# isis hello-interval 6 level-1
host1(config-if)# isis hello-multiplier 10 level-1
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Use the no version to restore a default value.
Configuring IS-IS Interface-Specific Parameters
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Chapter 6: Configuring IS-IS