3Com 8807 Configuration Manual page 298

298 C 30: RIP C
HAPTER ONFIGURATION
Configuring RIP Timers
n
Configuring RIP-1 Zero
Field Check of the
Interface Packet
By default, the interface receives and sends the RIP-1 packets. It will transmit
packets in multicast mode when the interface RIP version is set to RIP-2.
As mentioned previously, RIP has three timers: Period update, Timeout and
Garbage-collection. Modification of these timers affects RIP convergence speed.
Perform the following configuration in RIP view.
Table 265 Configure RIP timers
Operation
Configure RIP timers
Restore the default settings of RIP timers
The modification of RIP timers is validated immediately.
By default, the values of Period Update and Timeout timers are 30 seconds and
180 seconds respectively. The value of Garbage-collection timer is four times that
of Period Update timer: 120 seconds.
In fact, you may find that the timeout time of Garbage-collection timer is not
fixed. If Period Update timer is set to 30 seconds, Garbage-collection timer might
range from 90 to 120 seconds.
Before RIP completely deletes an unreachable route from the routing table, it
advertises the route by sending four Period Update packets with route metric of
16, so as to acknowledge all the neighbors that the route is unreachable. As
routes cannot always become unreachable at the point when a new period starts,
the actual value of Garbage-collection timer is three to four times that of Period
Update timer.
You must consider network performance when adjusting RIP timers, and configure
all the routers that are running RIP, so as to avoid unnecessary traffic or network
jitter.
According to the RFC1058, some fields in the RIP-1 packet must be 0, and they are
called zero fields. Therefore, when an interface version is set as RIP-1, the zero
field check should be performed on the packet. But if the value in the zero filed is
not zero, processing will be refused. As there is no zero field in the RIP-2 packet,
this configuration is invalid for RIP-2.
Perform the following configuration in RIP view.
Table 266 Configure zero field check of the interface packet
Operation
Configure zero field check on the RIP-1 packet checkzero
Disable zero field check on the RIP-1 packet
By default, RIP-1 performs zero field check on the packet.
Command
timers { update update-timer-length |
timeout timeout-timer-length } *
undo timers { update | timeout } *
Command
undo checkzero