in line ( like the skates )
""Nigel Taylor"" wrote in message news:200210202246.WAA27657@;groupstudy.com... > Chuck, > I can't believe anyone understood a word I wrote. After reading > my post I could only laugh. Nonetheless, I think you got what I was trying > to say and I do believe your thoughts and observations are correct. In > reading your post I was trying to recall what could have possibly provided > the material for the discussion you mentioned. > > The author that comes to mind is no other than "Terry Slattery". CL: Slattery remains an interesting read. A lot different, and maybe not a landmark work, a la Doyle, but still worth looking at. >I too did > notice the constant flapping of R4's common network using the "debug ip > routing" command. > I must say this is definitely interesting. Lately, I've had the opportunity > to look at a few situations where the use of RIP lead to some very unique > results as it pertains to redistribution. (check this one out... > http://www.cisco.com/warp/public/104/10.html). > Look at the route table on r2504 take note of the 3.22.x.x and 3.44.x.x > networks. Why is it on r2507 that the routes show as ospf exteranl type2 > routes. This is just another example of how rip simply works outside of the > rules. CL: I was going to say that it's because the routes are RIP routes that have been redistributed into OSPF. However, looking at the configuration, I see the interfaces are in the OSPF domain as well. Maybe the configuration is being misreported? Maybe if an interface is in both a RIP and an OSPF domain, RIP takes preference? That can't be right. CL: hhhmmmmmmm...... fooling around with the configs a bit. Mystery upon mystery. I can't duplicate the result on the CCO link below. I'm wondering if there are some IOS bugs. CL: the other thing I got to wondering is if there is some provision in the standard in the case of multiple ABSR's advertising the same route. I can't find anything off hand. It might require a more careful read than I have time for right now. > > Although, at first look everything does seem to be very straight-forward, > not until you get under the hood do you really see or observe the real > issues involved. Thanks for keeping us all sane :-) > > Nigel > > > > > ----- Original Message ----- > From: "The Long and Winding Road" > To: > Sent: Sunday, October 20, 2002 5:33 PM > Subject: Re: Update: OSPF Route mystery - what am I missing [7:55975] > > > > funny you should mention it. I've spent the last forty minutes looking at > > debugs on all of the routers involved. > > > > given the topology, > > > > R1--------tr----------R2 > > | | > > | serial | serial > > | | > > R4--------tr----------R3 > > > > R1, R2, and R3 are OSPF routers > > R1, R4, and R3 are RIP ver 2 routers > > > > 2 way redistribution occurs on R1 and R3. The configurations for > > redistribution are identical on both routers-- > > > > > > here is what I believe I am seeing: > > > > R4 is advertising RIP routes to both R1 and R3 > > > > R1 and R3, in turn, redistribute those routes into OSPF as E2's > > > > R2 receives those routes and installs them into the routing table. > > > > However, shortly thereafter R2 flushes those routes. Why? Well, looking at > > the debugs on R3 and R1, what is happening is that the E2 routes are > > replacing the RIP routes on R1 and R3. Then, depending on the timing, the > R4 > > routes show up in the R2 table sources from one router or the other. > > > > When I turn off mutual redistribution on R1 and R3, I start seeing results > > like this: > > > > O E2 160.160.30.0/24 is possibly down, > > routing via 160.160.255.2, TokenRing0 > > O E2 160.160.31.0/24 is possibly down, > > routing via 160.160.255.2, TokenRing0 > > O E2 160.160.32.0/24 is possibly down, > > routing via 160.160.255.2, TokenRing0 > > O E2 160.160.33.0/24 is possibly down, > > routing via 160.160.255.2, TokenRing0 > > O IA 160.160.39.0/26 is possibly down, > > routing via 160.160.255.2, TokenRing0 > > > > Note that 160.160.3X.0 routes originate on R3. I have similar things > > happening on R3 > > > > With mutual redistribution turned on, the situation is a bit different. > The > > routes just go round and round from router to router, being distributed > and > > redistributed forever, so that even though the domain is unstable, to the > > casual eye, everything is fine. All routes are reachable, although not > > necessarily via the interface over the protocol one would hope > > > > Nigel, I believe we have had this conversation before - about where the > > redistribution process goes to get the information it uses in the > > redistribution process. It is reasonable to think that when one > redistribute > > OSPF into something else, that the redistribution process goes to the OSPF > > database. For rip, where can it go but the routing table, and if all the > RIP > > routes have been replaced by OSPF routes, then it has nothing to > > redistribute? > > > > Not saying this is true, Just saying this is what appears to be true. > > > > Chuck > > > > > > ""Nigel Taylor"" wrote in message > > news:200210202001.UAA01188@;groupstudy.com... > > > Alright Chuck, John, > > > I looked at this little OSPF route > mystery > > > and let me say that whenever rip and ospf are involved in "mutual > > > redistribution" nothing is everything's a mystery. It took some thought > > but > > > I believe the answers to what you're observing resides within the > > > configuration of R1 and R3. Let's get the most important question > > > answered.. > > > > > > Did you configure filtering when performing redistribution? Not that > this > > > will help :-) > > > > > > Basically, the problem is that on R1 and R3 the ospf learned route for > the > > > common network on R4 is being proffered. The redistributing > routers(R1/R3) > > > see the best path to the r4 networks depending on which router(R1/R3) > > > cleared their routes or shut down a specific interface most recently. > This > > > is simply because the ospf form of the route(on R1/R3) has a better AD > > which > > > overrides the propagated rip routes from R4. Therefore, all R1 and R3 > both > > > will at times show R2 as the path to the R4 common networks.. > > > > > > Can someone say "distance" :-) > > > > > > Nigel > > > > > > > > > ----- Original Message ----- > > > From: "John Neiberger" > > > To: > > > Sent: Sunday, October 20, 2002 12:45 PM > > > Subject: Re: OSPF Route mystery - what am I missing. [7:55953] > > > > > > > > > > Chuck, > > > > > > > > I'm stumped so far, too. Did you try using some debugging? Perhaps > the > > > R2 > > > > might be able to give you a clue about why it's making that decision. > > > Debug > > > > ip routing might do the trick. If not, there must be some OSPF > debugging > > > > that would give us a hint. > > > > > > > > John > > > > ""The Long and Winding Road"" wrote in > > > > message news:200210200115.BAB17079@;groupstudy.com... > > > > > Or - what I believe versus what I see. > > > > > > > > > > > > > > > The topology: > > > > > > > > > > R1--------tr----------R2 > > > > > | | > > > > > | serial | serial > > > > > | | > > > > > R4--------tr----------R3 > > > > > > > > > > > > > > > R1, R2, and R3 are OSPF routers > > > > > R1, R4, and R3 are RIP ver 2 routers > > > > > > > > > > 2 way redistribution occurs on R1 and R3. The configurations for > > > > > redistribution are identical on both routers. > > > > > > > > > > There are uniquely identified routes assigned to loopback interfaces > > of > > > > all > > > > > routers. > > > > > > > > > > I believe I should see two paths to all of R2's interfaces on R4 ( > one > > > > > through R1 and the other through R3 ) > > > > > > > > > > I believe I should see two paths to all of R4's interfaces on R3 ( > one > > > > > through R1 and the other through R3 ) > > > > > > > > > > On R4 I do indeed see the two equal cost routes installed: > > > > > > > > > > R 160.160.254.254/32 [120/2] via 160.160.127.1, 00:00:18, > > Serial0 > > > > > [120/2] via 160.160.125.3, 00:00:17, > > > TokenRing0 > > > > > R 160.160.202.128/25 [120/2] via 160.160.127.1, 00:00:26, > > Serial0 > > > > > [120/2] via 160.160.125.3, 00:00:25, > > > TokenRing0 > > > > > R 160.160.200.0/24 [120/2] via 160.160.127.1, 00:00:27, > Serial0 > > > > > [120/2] via 160.160.125.3, 00:00:26, > > TokenRing0 > > > > > R 160.160.201.0/25 [120/2] via 160.160.127.1, 00:00:27, > Serial0 > > > > > [120/2] via 160.160.125.3, 00:00:26, > > TokenRing0 > > > > > R 160.160.204.0/27 [120/2] via 160.160.127.1, 00:00:27, > Serial0 > > > > > [120/2] via 160.160.125.3, 00:00:26, > > TokenRing0 > > > > > R 160.160.222.0/24 [120/2] via 160.160.127.1, 00:00:04, > Serial0 > > > > > [120/2] via 160.160.125.3, 00:00:05, > > TokenRing0 > > > > > Router_4# > > > > > > > > > > However, on R2, I do not see equal cost paths > > > > > > > > > > O E2 160.160.40.0/24 [110/20] via 160.160.254.3, 00:13:33, > Serial0 > > > > > O E2 160.160.41.0/24 [110/20] via 160.160.254.3, 00:13:33, > Serial0 > > > > > O E2 160.160.42.0/24 [110/20] via 160.160.254.3, 00:13:33, > Serial0 > > > > > O E2 160.160.43.0/24 [110/20] via 160.160.254.3, 00:13:33, > Serial0 > > > > > O E2 160.160.44.0/24 [110/20] via 160.160.254.3, 00:13:33, > Serial0 > > > > > O E2 160.160.45.0/24 [110/20] via 160.160.254.3, 00:13:35, > Serial0 > > > > > > > > > > Router_2# > > > > > > > > > > now here is the kicker. On R2, I shut down the serial interface > > between > > > R2 > > > > > and R3. Note that all the routes I am looking for show up over the > TR > > > > > interface. routes in the 160.160.10X.0 series are physically located > > on > > > > R1, > > > > > but are in the RIP domain. > > > > > > > > > > O E2 160.160.40.0/24 [110/20] via 160.160.255.1, 00:00:02, > > TokenRing0 > > > > > O E2 160.160.41.0/24 [110/20] via 160.160.255.1, 00:00:02, > > TokenRing0 > > > > > O E2 160.160.42.0/24 [110/20] via 160.160.255.1, 00:00:02, > > TokenRing0 > > > > > O E2 160.160.43.0/24 [110/20] via 160.160.255.1, 00:00:02, > > TokenRing0 > > > > > O E2 160.160.44.0/24 [110/20] via 160.160.255.1, 00:00:02, > > TokenRing0 > > > > > O E2 160.160.45.0/24 [110/20] via 160.160.255.1, 00:00:02, > > TokenRing0 > > > > > O E2 160.160.100.0/24 [110/20] via 160.160.255.1, 00:00:03, > > > TokenRing0 > > > > > O E2 160.160.101.0/24 [110/20] via 160.160.255.1, 00:00:03, > > > TokenRing0 > > > > > O E2 160.160.102.0/24 [110/20] via 160.160.255.1, 00:00:03, > > > TokenRing0 > > > > > O E2 160.160.103.0/24 [110/20] via 160.160.255.1, 00:00:03, > > > TokenRing0 > > > > > O E2 160.160.104.0/24 [110/20] via 160.160.255.1, 00:00:03, > > > TokenRing0 > > > > > O E2 > > > > > > > > > > Now I re-open the R2-R3 connection and observe that the routes homed > > on > > > R1 > > > > > still appear via the token ring interface, but the routes homes on > R4 > > > show > > > > > up via the serial interface. > > > > > > > > > > O E2 160.160.40.0/24 [110/20] via 160.160.254.3, 00:00:36, > Serial0 > > > > > O E2 160.160.41.0/24 [110/20] via 160.160.254.3, 00:00:36, > Serial0 > > > > > O E2 160.160.42.0/24 [110/20] via 160.160.254.3, 00:00:36, > Serial0 > > > > > O E2 160.160.43.0/24 [110/20] via 160.160.254.3, 00:00:36, > Serial0 > > > > > O E2 160.160.44.0/24 [110/20] via 160.160.254.3, 00:00:36, > Serial0 > > > > > O E2 160.160.45.0/24 [110/20] via 160.160.254.3, 00:00:36, > Serial0 > > > > > O E2 160.160.100.0/24 [110/20] via 160.160.255.1, 00:00:34, > > > TokenRing0 > > > > > O E2 160.160.101.0/24 [110/20] via 160.160.255.1, 00:00:34, > > > TokenRing0 > > > > > O E2 160.160.102.0/24 [110/20] via 160.160.255.1, 00:00:34, > > > TokenRing0 > > > > > O E2 160.160.103.0/24 [110/20] via 160.160.255.1, 00:00:34, > > > TokenRing0 > > > > > O E2 160.160.104.0/24 [110/20] via 160.160.255.1, 00:00:34, > > > TokenRing0 > > > > > O E2 > > > > > > > > > > > > > > > Now I'm thinking that with two redistribution points, and the routes > > > > > redistributed as E2's, where the cost does not change. > > > > > > > > > > As a sanity check, I created a loopback on both R1 and R3 with an > > > > identical > > > > > address 99.99.99.1/32. It took a bit of manipulating, but I managed > to > > > > > present both routes to R2 as equal cost. here is the routing table > > > > excerpt. > > > > > > > > > > O IA 99.99.99.1 [110/26] via 160.160.254.3, 00:00:01, Serial0 > > > > > [110/26] via 160.160.255.1, 00:00:01, TokenRing0 > > > > > > > > > > > > > > > So now, why is it that E2 routes, sourced from two different > > interfaces, > > > > > both with equal costs of 20, do not both appear in the R2 routing > > table > > > > > simultaneously. I "believe" this should not happen. > > > > > > > > > > Anyone gotta clue? I sure don't. > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > > www.chuckslongroad.info Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=55990&t=55975 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
