need to make a correction
wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Morgan > > Routers enter into their routing table routes to 'directly connected' > networks. In this case I will assume that, 192.168.3.0 is a directly > Connected Network for both RTA and RTB. This would be designated by C in the > routing Table. > > Even though you may be running IGRP on both routers, you are running them > with different processes or AS numbers. IGRP processes with different AS's > do not share information unless specifically configured to do so with the > redistribute command. > > If however RTA was running EIGRP with Process 100 and RTB was running IGRP > with Process 100, then the routers would share information. This is the only > time you don't have to do 'work' to make two different routing protocols > talk to each other. This of course only occurs when the Process numbers are > the same for EIGRP and IGRP. CL: the automatic redistribution will take place only if IGRP and EIGRP occur on the SAME router. There will be no eighbor relationship formed if on different routers. > If the AS numbers were different, then you once > again have to revert to Redistribute commands to make the routers learn each > others' routes. > > Looking at your example, the only 'common' network between RTA and RTB is > 192.168.3.0, the rest are unique hence RTA not showing .8 and .5 networks > and RTB not showing .2 and .5 networks > > Hope this clears this up. > > Manish > > -----Original Message----- > From: Morgan Hansen [mailto:[EMAIL PROTECTED]] > Sent: 04 July 2002 15:04 > To: [EMAIL PROTECTED] > Subject: AS numbers makes the difference right? [7:48099] > > > Guys, im going completely mental over here! Im afraid my brain is going to > go BOOM in a second! > > Heres the thing; > > Say you have 2 routers, with their respective routing tables right. > Router-A have these networks in its routing tabel: > > 192.168.2.0 > 192.168.3.0 > 192.168.4.0 > > And Rouer-B has these: > > 192.168.3.0 > 192.168.8.0 > 192.168.5.0 > > Now, what makes me crazy here is that I know that by looking at this, I can > tell that Router-A and Router-B have directly connected networks, and > therefore in Router-Bs routing tabel all of Router-As networks + Router-Bs > networks will show. > > But! Now this is a BIG BUT! > > If, say Router-A has the as number 100 (That is router igrp 100), and > Router-B has the as number 101 (router igrp 101). Then they are NOT directly > connected and therefor will not share routing table's right??? Or?? > > I mean, the as numbers decide this if im not entirelly wrong (which I most > def could be) Please, like ive said im going totally bananas over this and > need some help. > > If in fact Router-Bs routing table will show both Router-As and its own > networks, then. Is this because of the use of IGRP? Cause im reading the > Wendel Odom book here, and it says, I quote; > > "The following list summarizes the behavior of a router that uses the RIP-1 > or IGRP distance vector routing protocols: > > -Routers add DIRECTLY CONNECTED subnets to their routing tables. Routers do > not need to run a routing protocol to learn connected routes, but conneced > subnets routes are advertised to neighboring routers by the routing > protocol". > > Ok, this I know. But, im confused about the as numbers here (100 vs 101) > Because of this I would figure that Yes, Router-Bs routing table would > normally show us both Routers networks (being directly connected and > all) BUT, not when the as numbers are different. CL: you may want to adjust your thought process here, and move to a "top down" approach ( to borrow a phrase ) CL: routing protocols all have somewhat different methods of operation, based on different assumptions. RIP assumes one big flat network. OSPF assumes a structure based upon "areas", with a backbone at the center connecting various non backbone areas. BGP, IGRP, EIGRP assume "autonomous systems", but have provisions for connecting to other AS's. CL: so, in terms of how things are configured: RIP is configured in a straighforward manner, with no indication of process or area or AS. Router rip network x.x.x.x that's all there is. OSPF is configured in terms of area. However, over time it has been recognized that for whatever reason you may want to have different OSPF "processes" on the same router. Probably as one means of structuring very large networks. Howard could offer more insight as to the history of this. My understanding is that no routing protocol scales much above a couple thousand routers, and so an organization like a large bank with 15,000 routers might break its netowrk into a number of "regions" with a couple of core routers joining those regions together via redistribution of multiple OSPF processes. So with OSPF, you can insitute more than one OSPF process on the same router, and those two processes operate independently. router ospf 100 network a.b.c.d x.x.x.x area 0 router ospf 200 network e.f.g.h x.x.x.x area 0 two different processes. routers connected via network a.b.c.d will form adjacencies. routers connected via network e.f.g.h will form adjacencies. but the two "domains" will never learn eachother's routes, unless you redistribute between the two processes. Now we come to IGRP, EIGRP, and BGP. These protocols are all structured in such a way that the "router process number" is also the AS. With IGRP and EIGRP you can have multiple instances, each with a different AS / process number, and each operating independent domains, just like you can do with OSPF. BGP permits only a single instance, a single AS, a single BPG process on any one router, and neighbor relationships form due to different configurations. CL: yes there is a lot here, and it can be confusing, even to folks who have done this for a while. The key here is to distinguish between router processes, and autonomous systems, and then what the configuration of each routing protocol is telling you. But if you organize your thought process in some structured manner you will find it a LOT easier to navigate. CL: best wishes. keep at it. > > Guys, am I totally missing the point here? Please help me figure this one > out! Im loosing it :-( > > Morgan > mailto:[EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=48121&t=48099 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
