User's Manual

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Adjusting the time interval of BEIGRP to send "hello" messages and the
timeout death time of the neighbors
BEIGRP hello protocol archieves 3 objectives to enable correct BEIGRP operation:
 It discovers accessible new neighbors. The discovery is automatic and requires no
manual configuration;
 It checks neighbors’ configuration and only permits communication with the neighbours
configured with compatible mode.
 It continues to maintain the availability of the neighbors and detects the disappearance of
the neighbors.
The router sends “hello” multicast packet on all interfaces running BEIGRP. All routers support BEIGRP receive
these multicast groups, so that it can discover all neighbours.
“Hello” protocol uses two timers to detect the disappearance of the neighbours: hello interval defines the
frequency of sending BEIGRP hello messages on the interface of the router, while hold timer defines the
interval of time the router has to wait for the communication data from the designated neighbor before the
declaration of the neighbour’s death. We ordered that every time it receives BEIGRP packet from the neighbour
router, it resets the hold timer.
Different network type or network bandwidth will use different default value of hello timer:
Interface type encapsulation Hello timer
(second)
Hold timer
(second)
LAN
inte
rfac
e
Any 5 15
WAN
inte
rfac
e
HDLC or PPP 5 15
NBMA interface,
bandwidth<=T1
60 180
NBMA interface,
bandwidth>T1
5 15
The point-to-point sub-
interface of NBMA interface
5 15
The difference of the default value of the timer in Hello protocol may induce the result that the BEIGRP
neighbours connected to different IP sub-network use different hello and hold timer. To resolve the problem,
the hello packet of every router designates its own hold timer, every BEIGRP router uses neighbour’s the
designated hold timer of the hello group to decide the timeout of this neighbour. Here, it can enable the
appearance of different neighbour error detection timers in the different stands of the same WAN nephogram.
But under some particular situation, the default value of the timer cannot be met, so if you want to adjust the
time interval of sending hello messages, use the following command:
Command Purpose
ip beigrp hello-interval
seconds Adjust the time interval of sending hello message from
this interface