ROUTING INFORMATION PROTOCOL (RIP)

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RIP protocol distance vector protocol, it works on small networks. Routers only know the address of the interface they are connected to. But if the routing is correct, you need to know the address of the other routers and their interfaces. Distance vectors do not place the entire network image in routing protocols only address the routers of the next step. But in the case of the Link State Routing Protocol, the entire network map is available. The features of the Routing Information Protocol (RIP) can be considered by considering:

The Best Concept Of RIP Protocol
Figure: RIP Protocol
  • Each router on the Internetwork has its own identity and sends its identity directly to the routers connected to it.
  • During the router boot-up process, the entire routing table is forwarded to all neighboring routers.
  • Routing updates are sent to neighboring routers every 5 seconds, and updates can be sent only when a route is changed.
  • Each router determines the shortest way to send packets to another network via a neighboring router.

Due to the protocol constraint, the convergence of the RIP is very slow. So in large networks, it should not be used. However, this is only useful for a network of autonomous systems. RIP is considered as an interior gateway protocol and was designed for use on smaller networks. It works well within the same routing domain. Cisco routers can have multiple routing protocols running at the same time.

The protocol for which routers will be used has been set to prioritize these protocols, called administrative distances (AD). The route with the lowest AD will be chosen. The table below shows the Administrative Distance (AD) of the routers from different sources.

Routing Protocol Administrative Distance
Direct connection 0
Static Route 1
EIGRP Summary Route 5
External BGP 20
Internal EIGRP 90
IGRP 100
OSPF 110
IS-IS 115
RIP 120
EGP 140
On-Demand Routing 160
External EIGRP 170
Internal BGP 200
Unknown 255

Then it appears that the administrative distance of the route known through RIP is 120.

Routing tables updates and hop count

RIP protocol relies primarily on the hop count to determine the path and distance to the destination network. The route to which a packet is sent depends on how many routers it crosses. According to Rip, low hop means it’s a short distance away. If there are two routes to reach a network; one is Hope Count 5 and the other is Hope Count 6, so RIP will choose the first route – through its actual distance is higher than the second.

Routing tables updates and hop count
Figure: RIP Hop Count

Route selection through this hop count actually disables RIP because the speed of the route is not emphasized here. There may be routes whose hop count is high but bandwidth is high due to that, the packet can go a long way. RIP does not take into account such routes.

Routing tables updates

With a packet that does not have to go from one router to the other for eternity, the rip gives a maximum hop count or its lifetime (TTL). The default maximum hop count of RIP is 15, that is, it can exceed a maximum of 15 routers whenever the data packet crosses the router at the corner, its TTL decreases by 1. Thus, it went to zero on the 5th router, and still, the packet was canceled if it did not reach the destination. If not, that packet would cause a routing loop from the network.

When a new routing update is received, the router looks at the routing table stored on its own. If the update provides information about the route in the new corner, the router then parses that information into its routing table. This increases the metric of that route by 1, and the sender’s IP address is queried as to the next-hop address on that route.

The router then updates that for convergence immediately sends it to the neighboring routers. If the route sent by the update is present in the routing table and the metric for the updated route is less than the saved route, then the existing route information is replaced with new information.

Eliminate routing errors

RIP protocol relies on neighboring routing devices to find the most efficient way to reach the destination. Every 30 seconds, every router sends its updates. Problems arise when all of these neighboring routers have a sudden upset. In this case, the downed routers cannot tell that it is ‘down’. Then the following things happen.

  • If after 90 seconds the router does not contact the router, then the router is considered invalid.
  • After 180 seconds the hold down reaches the timer, and RIP assumes that the route is no longer there. The neighboring routers were then informed that it was not a router.
  • After 270 seconds, no more information about that route is available if the flush timer deletes the route from the routing table.

The hop count value can be a maximum of 15 so that the routing loop does not occur. Without this maximum hop count, a routing loop would occur and the packet would rotate from the router to the router. RIP split horizon with poison reverse method is also used to avoid the routing loop.

Convergence and timers

RIP Protocol convergence is used to keep the routing table accurate and updated. Convergence synchronizes the routing tables of all routing devices. When the network is large, the convergence process sends continuous update updates every 30 seconds to the RIP and all routers can update their respective routing tables accordingly. When a router is suddenly changed, information is immediately called a triggered update.

Routing tables are likely to be different on each router if routers are not converted. If a router is not updated, it may affect other routers with false information. The hold-down timer is used so that the failed router is not propagated to other routers as before. During this time all routers will know that there is a link disrupted. Then it is seen again whether it is moving, and when it is activated a new update is given.

In the case of RIP, the following are important to keep in mind:

  • The hop count is a maximum of 15.
  • RIP sends routing updates every 30 seconds.
  • Routing updates are sent to UDP port 520.
  • It is unintelligent that the path is chosen based on the hop count.
  • In large networks, its convergence is very difficult.
  • It uses very little processing power and memory.
  • Useful for single autonomous systems or small networks.
  • Almost all hardware manufacturers and software developers support RIP.

RIPv1 and RIPv2

Xerox Corporation created Routing Information Protocol version 1. The main difference between RIPv1 and RIPv2 is that RIPv1 does not contain subnet information, but RIPv2 has subnet information. The following table shows the comparison of RIPy1 and RIPv2.

RIPv1 RIPv2
Distance Vector Protocol Distance Vector Protocol
The hop count is a maximum of 15 The hop count is a maximum of 15.
Classful Classless
Broadcast based Using multicast 224.0.0.9
Does not support VLSM Supports VLSM
No authentication Supports MD5 authentication
Do not support networks that are not in the same category Network support that is not in the same category
The subnet mask with the packet does not send information Sends subnet mask information to packets

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