NOTES CCNP ROUTE :
ROUTING INFORMATION PROTOCOL
Routing AD METRIC Routing Rfc2453, timers
Protocol UDP value updates year 1993
RIP 520 120 Hop count
Rip ver. 1 15,(including Broadcast classful
self-16).
Rip ver. 2 Multicast Classless, supports Update 30
224.0.0.9 authentication Invalid 180
Flush 240
Hold- 180
down
RIP :
RIP is distance vector protocol.
Rip runs in two versions, RIP v1, and RIP v 2.
RIP uses UDP port 520 and it has AD value 120.
RIP v1 uses broadcast for sending routing updates every 30 seconds.
Rip v2 uses multicast address 224.0.0.9 for routing updates every 30 seconds.
Metric used is HOP count and it uses Bellfordhaffman algorithm to make routing decisions.
The maximum hop count is 15 and including oneself it is 16.
Suitable for small networks having similar links.
RIP timers include:
Invalid Timer: 180 seconds. How long the router waits before declaring a route as dead. after
invalid timer expires the route is marked dead and its metric value changed to 16
unreachable in rip and advertised to other routers in the rip neighborship.so that
every router in the rip network marks the route as dead .this process is called route
poisoning. This helps in preventing routing loops.
Flush Timer: 240 seconds. The time for which the dead route is advertised to other routers and
flushed out of the routing table
UpdateTimer: Advertisers regularly the entire routing tables every 30 seconds. At the broadcast
address or multicast address 224.0.0.9 for rip version2.
Hold Down Timer :180 seconds once an entry in the routing table is added,deleted,modified
i.e,updated then ignore any updates to the route for the duration of hold down
timer or until the hold down timer expires.
NOTES CCNP ROUTE :
What are Routing loop prevention techniques in RIP?
Hold Down Timer : once an entry in the routing table is added,deleted,modified i.e,updated
then ignore any updates to the route for the duration of hold down timer or
until the hold down timer expires.
Route poisoning: increase the hop count to infinity i.e. 16 so as to make that route dead to
other routers and advertise till the flush timer of value 240 sec expires.
Split horizon never advertise route back to through the interface through which it is
received.
Triggered updates as soon as routing update is received advertise to your immediate
neighbours, don’t wait for the update timer.
Poison reverse if a route update is received that contains information about a dead route
from one interface and receives update about the same route from different
interface then it will advertise that route as dead through that latter
interface also.
Limit the number of hop counts to infinity:
Also the number of hop counts to infinity can be changed to some smaller
value from default value of 16. So as to stop propagation of false route
advertisements.
LOAD BALANCING IN RIP
By default, RIP can load balance 4 equal cost paths to destination, but it can be configured to have
Values between 2 and 6.
Passive-interface command:
Passive interface is rip sub-configuration command to stop advertising rip updates to the interface
on which there is no interface of router running rip is connected. Suppose
the network advertised is a LAN segment subnet address which will not have
any router connected.
Router (config) #routers rip
Router (config-router) # passive-interface interface f0/0
In other words, in stub networks in which there are no neighbouring rip routers to advertise the RIP
routing updates, the passive-interface command may be used.
