Transcript No Slide Title

Objectives
After completing this chapter you will be able to:
 Describe the Routing Information Protocol (RIP version 1
and RIP version 2)
 Describe Routing Loops, Split Horizons and Poison
Reverse
 Outline the advantages and disadvantages of RIP
Characteristics of RIP
 RIP is a very simple protocol of the distance vector
family. RIP was documented in RFC-1058 in June 1988 .
 RIP messages can be broadly classified into two types:
Routing information messages and messages used to
request information.
 RIP uses a very simple metric - the hop count.
 RIP packets are carried over User Data Protocol (UDP)
and IP. The RIP processes uses UDP port number 520.
RIP updates are normally sent every 30 seconds by
default.
 Every entry has a timer (180 seconds by default)
associated with it and on expiry the distance for that
entry is set to infinity.
Routing Table From Ericsson Colorado Router
Destination Route Mask
Next Hop
Port Met Typ Src Age
192.168.10.0 255.255.255.0 192.168.10.1 J3 0 DIR LOC 113
192.168.10.1 255.255.255.255 192.168.10.1 J3
0 DIR LOC 113
192.168.11.0 255.255.255.0 192.168.10.2 J3 1 REM RIP 31
192.168.12.0 255.255.255.0 192.168.12.2 J4 0 DIR LOC 114
192.168.12.2 255.255.255.255 192.168.12.2 J4
0 DIR LOC 114
RIP Version 1 Message Format
0
8
Command(1)
16
Version (1)
24
Must be zero (2)
Address family identifier (2) Must be zero (2)
IP address (4)
Must be zero (4)
Must be zero (4)
Metric (4)
1 - request
2 - Response
3 - Traceon
4 - Traceoff
5 - Reserved
IP header
Address family identifier = 2 (IP)
UDP Port=520
31
The RIP Protocol
RIP Request
…………………
…………………
…………………
………………….
RIP Response (Max 25 entries)
Valid Class A, B or C?
Net number =/ 127 or 0
Host number =/ broadcast
Metric >/ 16
Metric = Metric+1
Update Routing table
RIP Neighbours
Broadcast Networks
NBMA Networks
ATM
Ethernet
RIP behaves promiscuously
RIP neighbours are defined
RIP Version 2 Message Format
0
8
Command(1)
16
Version (1)
24
Routing domain (2)
Address family identifier (2) Route tag (2)
IP address (4)
Subnet mask (4)
Next hop (4)
Metric (4)
31
Slow Convergence
A
B
Network Hops
C
Network Hops
D
Network Hops
A
1
A
2
A
3
B
1
B
1
B
2
C
2
C
1
C
1
D
3
D
2
D
1
Routing Loops
A
B
C
2
1
2
1
3
3
4
4
5
5
6
6
D
E
Split Horizons
A
B
C
2
1
2
1
3
3
4
4
5
5
6
6
D
E
Advantages of RIP
 RIP automatically creates and maintains a network of
routes.
 Since RIP uses a single metric it is very easy to
configure.
Disadvantages of RIP
 The diameter of the internetwork is limited to 15 router
hops.
 Network administrators cannot take into account such
factors as bandwidth or delay when configuring their
routing systems using RIP.
 Each routing entry is updated every 30 seconds or so,
regardless whether there has been a change in the
network topology or not.