BROCADE IP PRIMER

Console49F Link 50F1Power1F 2F 3F 4F325476981110131215141716191821202322252427262928313033323534373639384140434245444746 4849F Link 50FPower11F 2F 3F 4F32Console5476981110131215141716191821202322252427262928313033323534373639384140434245444746 4849F Link 50FPower11F 2F 3F 4F32Console5476981110131215141716191821202322252427262928313033323534373639384140434245444746 48Routing Information Protocol (RIP)whatever reason, the router now has an alternative. Duplicates in your routingtable are actually a good thing. They provide redundancy, and redundancymeans more up time, and less complaints from your users.Routing Information Protocol (RIP)Let's talk about a specific dynamic routing protocol: Routing Information Protocol(RIP). RIP is the fundamental routing protocol. It is one of the oldestdynamic routing protocols. It is very simple in its design. When a router is configuredwith RIP, it will send its entire routing table out all of its participatinginterfaces, by default, every 30 seconds. The routing table is contained inpackets, but encapsulated using UDP port 520 for delivery. All other routersthat are configured with RIP and are within this router's broadcast domain willreceive the broadcast, and add the newly discovered routing information intotheir own table. They, in turn, will broadcast their entire routing table to anyonewho will listen.RIP is referred to as a distance vector routing protocol. This term describeshow the routing protocol makes its decisions. In other words, what happenswhen a router learns two (or more) different routes for the same network? Howdoes it choose? In RIP, this depends on distance. It measures distance byhops. A hop count is how many routers the packet would have to pass throughto get to its destination. Let's look at our example again.Switch Be2192.168.1.2/30ve20172.17.0.1/24e2192.168.2./30e1192.168.1.1/30Switch AHost B172.17.0.10/24e1192.168.2.1/30Switch Cve10172.16.0.1/24e2192.168.3.1/30e2192.168.3.2/30ve30172.18.0.1/24Host A172.16.0.10/24Host C172.18.0.10/24If Switch A wanted to talk to Switch C, it's got two choices. One, it could speakto Switch C directly on its 192.168.3.0/30 network link. Or two, it could handoff to Switch B, using its 192.168.1.0/30 link, and let Switch B forward it toSwitch C using its 192.168.2.0/30 link. If RIP were employed, which would itchoose? The path going from Switch A to Switch C is one hop. The path goingfrom Switch A to Switch B and then to Switch C is two hops. RIP would choosethe direct path from Switch A to Switch C. It has the shorter hop count. This isthe only characteristic RIP uses to make its routing decision. It is a distancevector protocol.When RIP was developed, the concept of having an infrastructure so big thatyour packet would have to travel through more than 15 routers was laughable.We know this today to be quite short-sighted. But this characteristic still existswith RIP today. It can only comprehend routes whose hop counts are from 1 toBrocade IP Primer 231