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The Big RIP-Off

Today’s tech tip is primarily for people dealing with larger networks, large enough to use multiple subnets. Any of the rest of you who are insatiably curious about obscure technical information are welcome to read along. The topic is RIP, the Routing Information Protocol.

Servers using RIP function as routers that know which other routers are adjacent to them, and they share that information with each other so that all routers in the network can create a table of the other routers and their relationship to each other. The RIP servers actually announce their routing tables to each other every 30 seconds. The result is that each router has a complete table with which to compute the most efficient routing for any packet.

A RIP server is typically used in an environment with several networks or subnets that need to communicate to each other. Separate subnets may be used because there is a limit of 255 nodes per subnet, or because the subnets are separated by location or function, or simply to cut down on network traffic. For example, a company might have three subnets connected with RIP servers, designated as A, B and C. Subnet A sees only its own traffic, plus the packets from subnet B and C that are actually addressed to subnet A systems, rather than all of the traffic combined.

Bottlenecks are avoided (or at least postponed) by eliminating the unnecessary traffic. Because the RIP servers share their tables with each other, the administrator does not need to manually update routing information whenever there are changes or additions to any of the subnets. Each of the subnets could also be called an ‘IP network’. An IP network is a cabling system bounded by one or more routers.

RIP Versions

There are two versions of RIP available, imaginatively called RIP version 1 and RIP version 2. RIP version 1 has less capability, but it is also easier to configure. RIP 2 is more complex to use, but it gives you advanced capabilities such as peer security, route filtering, and fund transfers into my bank account (just kidding about that last one).

To make troubleshooting and problem isolation easier, it is recommended that you deploy RIP by first setting up and testing the basic configuration. Then, add advanced capabilities one at a time, testing after each feature is added.

Deploying RIP for IP

Here is the step-by-step process for deploying RIP:

1. Draw a map of the topology of your IP internetwork that shows the separate networks and the placement of routers and hosts.
   
   
2. For each IP network, assign a unique IP network ID, also known as an IP network address. This is the first portion of an IP address, and it is the same for all host systems in that network. It may include 1, 2 or 3 octets, depending on the class of IP address being used. The remaining octet(s) of the IP address is for the host address, and this will be different for each system. Together the network ID and host addresses make up the full range of IP addresses available to that IP network.
   
   
3. Assign IP addresses to each router interface. The common industry practice is to assign to the router the first IP address in the range. For instance, if the network ID is 192.168.100.0 (with a subnet mask of 255.255.255.0), the router interface for that IP network would be assigned an address of 192.168.100.1
   
   
4. For each router interface, designate whether that interface will be RIP v1 or RIP v2. If the interface is RIP v2, designate either broadcasting or multicasting for announcements. Broadcast announcements go to all nodes, while multicast announcements only go to a select group.
   
   
5. For Windows 2000 servers (and later), RIP is combined with Remote Access Service (RAS) to create RRAS (Routing and Remote Access Service). For each server running RRAS, add the RIP protocol and configure the interface as RIP v1 or v2 as appropriate. As soon as each RIP server is initialized, it will begin announcing its routing table, and collecting routing data from the other servers.
   
   
6. When the configuration is complete, allow a few minutes for the routers to update each other’s tables before testing the internetwork. At this point, all of the servers and workstations on the different subnets should be able to communicate and exchange data with each other.
   

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