Computer Networks & Internetworking Routing Information Protocol(RIP)

1. Routing Information Protocol
(RIP)
Sarhad University PeshawarSarhad University Peshawar
Computer Networks & Internetworking
LECT 04
6th
Semester

3. RIP -- What is it?
RIP is a routing protocol for exchanging routing table information
between routers.
• Routing updates must be passed between routers so that they can make the
proper choice on how to route a packet.

4. RIP Characteristics
Distance vector routing protocol.
Uses hop count as a path selection metric.
Three types of timers.
Multiple stability features.

5. Distance Vector Routing Protocol
Each router sends all
or part of its routing
table in routing updates.
However, the updates
are only sent to
neighboring routers.
Cisco Systems Inc.

6. Hop Count -- Fifteen Hop Limit
Hop count is the sum of all the legs in a route.Hop count is the sum of all the legs in a route.
– After 15 hops, the packet is discardedAfter 15 hops, the packet is discarded
Lucent Technologies

7. Timers
Routing-update timer
By default, routers send updates every 30 seconds.
A small random number is added to prevent collisions.
Route timeout
A route timeout timer is associated with a route. When it
expires, the route is marked invalid.
Route-flush timer
After the route timeout expires, the route-flush timer
eventually expires, deleting the route from the table.

8. Multiple Stability Features
Split Horizon
Information learned about a route is not sent
back out the interface it was learned from.
Hold-down mechanisms
When a link in a route fails, that route is put in
a hold-down state, where routers neither send
or receive updates about that route.

9. Rip Packet
A -- Command - request or response.
B -- Version # - specifies version of RIP.
C -- Zero - Not used.
D -- Address Family Identifier (AFI) - Indicates
type of address being specified (IP, IPX, etc)
E -- Address - Specifies IP address of entry.
F -- Metric - # of hops traversed from source to
destination
1 1 2 2 2 4 4 4 4
A B C D C E C C F

10. Drawbacks
RIP version 1 does not recognize subnets.
This feature was added in RIP version 2.
Because RIP only uses hop count as a metric,
packets may be forced to take a slower route with
less hops over a faster route with more hops.
Other routing protocols use a combination of
different metrics to calculate a route.