Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - IP-IPV6-IGP CONFIGURATION GUIDE 2010-10-31 Configuration Manual page 364

Software for e series broadband services routers ip, ipv6, and igp configuration guide
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JunosE 11.3.x IP, IPv6, and IGP Configuration Guide
340
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.
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.
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.
Using a smaller hello-multiplier will give fast convergence, but can result in more
routing instability.
Increment the hello-multiplier to a larger value to help network stability when needed.
CAUTION: Never configure a hello-multiplier lower than the default.
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.
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.
Example
host1(config-if)#isis hello-interval 6 level-1
host1(config-if)#isis hello-multiplier 10 level-1
Use the no version to restore a default value.
See isis hello-interval
See isis hello-multiplier
Copyright © 2010, Juniper Networks, Inc.

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