Matt, The 'ip classless' and 'no ip classless' have to do with the way the router forwards packets. The commands don't have an effect on the routing protocols themselves. The best routes from the routing protocols will be put int the Routing Information Base (RIB).
With 'ip classless' the router looks up the route with the longest-match and uses that. With 'no ip classless' it's different. Lets say you have 2 directly connected interfaces of 172.16.1.x/24 and 172.16.2.x/24 and a default route pointing to 172.16.1.2 which is an adjancent router off the first interface. Now, a packet comes in the router with a destination of 172.16.9.x. In a classful world, the router see's it as 172.16.0.0 and saids I have interfaces in that classful range but no 172.16.9.x so it drops it. In a classless world, longest-match rule is in effect so it uses the route that matches it best which would be the default route to 172.16.1.2. HTH. Also, this effects all router vendors (not just cisco) but most have classless enabled by default these days (BayRS doesn't though). Erick B. > > ""Matt Saunders"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Hi Group, > > > > > > Im really struggling to understand the > requirement in using the ip > > classless > > > command when you are configuring a default > route. > > > > > > I noticed that RIP 2 is a classless protocol & > RIP ver 1 is a classfull. > > > > > > Can anyone help me understand what the > difference is (in simple terms!!) > > as > > > i want to move on with my studies though im sure > this is something thats > > > going to come up again!!!! > > > > > > Cheers > > > > > > Matt __________________________________________________ Do You Yahoo!? Yahoo! Sports - live college hoops coverage http://sports.yahoo.com/ Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=38875&t=38875 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
