RIP

Routing Information Protocol

It is one of the most commonly used interior gateway protocol (IGP) routing protocols.

It is a distance vector dynamic routing protocol, it sends an update of its complete routing table information to other routers for every 30 secs on the UDP port 520.

Rip uses the bellman ford algorithm to determine the best path to a particular destination, and it is no. of hops.

Its administrative distance is 120.

It is used in the small networks like a maximum of 15 routers.

It has two versions:

version 1 is the classful, its does not support vlsm and cidr.

It broadcasts its updates on 255.255.255.255

It only supports automatic summarization,

It does not support authentication.

The router will add the default mask of the local interface update belong to the same major network.

Example: local interface ip: 10.1.1.1 and update is from 10.2.2.2, then the receiving router 10.1.1.1/16 will apply the subnet mask of /16 to the update received from 10.2.2.2

Or The router will apply the default classful subnet mask, if the update is not from the same major network.

Example: local interface ip: 10.1.1.1 and update is form 11.1.1.1, so the receiving router will apply /8 subnet mask to the route.

and version 2 is classless, it supports vlsm and cidr.

It multicasts its updates on 255.255.255.9             

It supports both automatic and manual summarization on any router

It supports authentication.

Configuring classful and classless:

Router(config)# no ip classless

Router(config)#ip classless

Its update time is 30 seconds

Invalid time is 180 seconds

Hold time is 180 seconds

Flush time is 240 seconds

These timings are based on last received update.

Configuring RIP

Enabling rip:                                          (config)#router rip

Enabling rip on interfaces for

sending and receiving updates:               (config-router)#network  classful_network_address

Enabling unicast rip updates

Used in NBMA networks:                     (config-router)#neighbor ip-address

 

Adjusting timers:                                    (config-router)#timers basic update(secs) invalid(secs) holddown(secs) flush(secs)

Passive interface:                                   (config-router)#passive-interface default

                                                             Sets all interfaces to passive by default.

                                                             (config-router)#passive-interface type number

                                                             Sets only the interface mentioned in the type and  number.

Note: Passive-interface cmd in RIP stops sending updates but still receive updates. Where as in EIGRP and OSPF stops both sending and receiving updates, this will also stop the formation of neighbor relationship.

Also the neighbor command does not disable the regular updates, so we have to use passive-interface command to disable those updates to use neighbor command. Where as in EIGRP and OSPF the neighbor command disables all update msgs.

Authentication: parameters                    (config)#key chain name (name: does not need to be same  on both the routers)

(config)#key number (number: does not need to be same on both routers unless if using md5)

(config)#key-string password_used (should be same on both routers)

Authentication: Enabling

(config-if)# ip rip authentication key-chain name of the chain

(config-if)#ip rip authentication mode {text | md5}

Router summarization:                           (config-if)# ip summary-address rip ip-address ip_network_mask

                                                            (config-if)#no ip split-horizon

Note:

we have to disable split horizon, for auto summarization and manual summary to be advertised. Auto summarization will override the manual summarization on the given interface, except when both of the following conditions are true.

Split horizon

Is used to reduce the possibility of routing loops main in Distance-vector routing protocols. It will not advertise the route back to a router, from which the route has originated. we should enable split horizon in NBMA networks. Where as in NON-NBMA like Frame-relay and Switched Multimedia Digital Systems, the situation is different, we should enable split horizon.

Enabling split horizon:                           (config-if)#ip split-horizon

Disabling split horizon:                          (config-if)#no ip split-horizon

Configuring an interpacket delay

If packets are being sent from
high end router to a low end router,
 we use this command:                         (config-router)#output-delay delay(8-50ms)

Connecting RIP to a WAN

Using RIP in WAN creates two problems, as WAN’s are established on demand and relinquished traffic subsides.
so RIP’s periodic updates prevent WAN from closing the circuit.
and even on fixed, point-to-point links, the overhead of periodic RIP transmission will interrupt normal data transfers. To overcome these limitations triggered extensions to RIP cause RIP to send updates only when there has been a routing update.

Enabling Triggered rip:                         (config-if)#ip rip triggered

To see the RIP private database:          show ip rip database (used when triggered extension is used)

Applying offsets to a routing metrics:    (router-config)#offset-list {acl number | acl name} offset                                                                           [int type int num]

Used to change the metrics of the 

incoming/outgoing routes on rip 

and igrp.

Disabling the validation of source ip address:

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Default Routes in RIP :

Cisco supports five basic methods of advertising default routes with IGPs. The one method which is used to advertise the default route is to redistribute one routing protocol’s default route to another routing protocol, which is discussed in the REDISTRIBUTE topic. The other four types are discussed here:

Feature	RIP	EIGRP	OSPF
Static route to 0.0.0.0 with the redistribute static command	Yes	Yes	No
The default-information originate command	Yes	No	Yes
The IP default-network command	Yes	Yes	No
Using summary routes	No	Yes	No

Note: cisco does not recommend the use of summary static routes.

Static Route to 0.0.0.0 with the redistribute static command:

• The redistribute static command must be configured on the same local router.

• Metric can be left to default or set, by two methods

                   Redistribute static metric x,  or

                   Default-metric x,

• Redistribute static can refer to a route-map,