BROCADE IP PRIMER

Console49F Link 50F1Power1F 2F 3F 4F325476981110131215141716191821202322252427262928313033323534373639384140434245444746 4849F Link 50FPower11F 2F 3F 4F32Console5476981110131215141716191821202322252427262928313033323534373639384140434245444746 4849F Link 50FPower11F 2F 3F 4F32Console5476981110131215141716191821202322252427262928313033323534373639384140434245444746 48Dynamic Routing ProtocolsNow, in a real dynamic routing protocol, the conversations would not normallybe this slow or this serial (one right after the other). I broke it up for you toshow you how the conversations affect the routers in the environment. In reallife, these conversations would be happening almost simultaneously, dependingon the dynamic routing protocol you've chosen.So now, Switch A knows all of Switch B's and Switch C's routes. Switch B knowsall of Switch A's and Switch C's routes. And, of course, Switch C knows all ofSwitch A's and Switch B's routes. If I tried to ping Host C from Host A, would itwork? Sure! All of the routers know how to get my packet there and back again.And I didn't have to configure one static route! All I had to do was enable adynamic routing protocol, and let the routers do the talking.But it gets better. What happens when there's a change in the network? Let'sthrow in this little curve ball.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 C172.18.0.10/24We've added a new subnet (192.168.3.0/30 between Switch A and Switch C),and we've added another link. What happens to our switches' routing table?Not to worry, friends. Did we not say that it was a dynamic routing protocol?Switch A and Switch C detect the change, and inform Switch B (as well as eachother) of the new route.But wait a minute! Don't we have a loop now? For example, if Switch A wants toget to Switch C, it's got two choices. It could go directly to Switch C via the192.168.3.0/30 network, or it could get there the way it used to get there(through Switch B). Which will it choose?That's actually a deep question. It actually depends on the dynamic routingprotocol you've chosen. We'll go more into that later on. But the importantthing for you to know now is that the router will make a decision, and, mostoften, will stick to that decision unless there's a change in the network.“So, you're saying that if one of those links goes down, my routers will detectthe failure and route traffic through another link automatically?!” Yep, that'sexactly what I'm saying. It's a beautiful thing, isn't it? The routers know theiroptions and they will adjust their routing tables to accommodate the change.Some examples of dynamic routing protocols that we'll be discussing includeRIP, OSPF, and BGP. Love the dynamic routing protocol!Brocade IP Primer 229