I wonder if you found the case where split horizon doesn't work. Radia Perlman talks about this. She shows the routers in a triangle. Check page 305 of her 2nd edition of Interconnections.
In her example the failure happens after an interface goes down though and it's not related to IGRP and EIGRP interacting..... :-) Anyway, in some situations you need poison reverse and holddowns too, which EIGRP does have. Split horizon isn't perfect. Priscilla The Long and Winding Road wrote: > > clarification: > > R2 > loop = 222.222.222.2/32 > IGRP 100 > loopback is in the igrp domain > > R3 > loop = 222.222.222.3/32 > IGRP 100 > EIGRP 200 > loopback is in the eigrp domain > > R2 SHOULD be advertising 222.222.222.0/24 to R3. And it is. > > However, R3 is also advertising 222.222.222.0/24 to R2 > > Split horizon IS enable. I checked that. > > I watched debug traces for an hour, and was writing my post > when it occurred > to me that eigrp was interacting with igrp. > > 222.222.222.0/24 is variably subnetted, 3 subnets, 2 masks > C 222.222.222.4/32 is directly connected, Loopback1001 > O IA 222.222.222.5/32 [110/65] via 199.45.1.5, 10:53:34, > Serial1 > I 222.222.222.0/24 is possibly down, > routing via 199.34.1.3, Serial0 > 199.34.1.0/29 is subnetted, 1 subnets > C 199.34.1.0 is directly connected, Serial0 > 199.45.1.0/27 is subnetted, 1 subnets > C 199.45.1.0 is directly connected, Serial1 > C 199.1.1.0/24 is directly connected, TokenRing0 > Router_2# > > 222.222.222.0/24 is variably subnetted, 2 subnets, 2 masks > C 222.222.222.3/32 is directly connected, Loopback1001 > I 222.222.222.0/24 [100/8976] via 199.34.1.4, 00:02:19, > Serial0 > 199.34.1.0/29 is subnetted, 1 subnets > C 199.34.1.0 is directly connected, Serial0 > 199.35.1.0/28 is subnetted, 1 subnets > C 199.35.1.0 is directly connected, Serial1 > C 199.1.1.0/24 is directly connected, TokenRing0 > C 193.1.1.0/24 is directly connected, Loopback1 > Router_3# > > the "possibly down" moves from router to router slowly, as the > dead time > expires. > > the "problem" as I see it, it that EIGRP and IGRP are > interacting. If I > remove 222.222.222.0 from the eigrp process, the problem > disappears. > > as a matter of intellect, it could well be a split horizon type > issue, in > that both routers believe they are the source of 222.222.222.0 > ( igrp on r2 > and eigrp on r3 ) on the other hand, automatic summarization > was turned off. > > in my mind, there is some thing happening within the code that > is the cause > of this problem. as I said, I thought igrp and eigrp interacted > only if both > were in the same AS on the same router. > > > > ""Larry Letterman"" wrote in message > news:[EMAIL PROTECTED] > > r3 sends to r2, then r2 sends back to r3.. > > you sure about that...split horizon should be enabled for > > eigrp and igrp..and igrp and eigrp will work together in the > > same as number..not sure about different as #'s.... > > > > Larry Letterman > > Network Engineer > > Cisco Systems > > > > > > ----- Original Message ----- > > From: The Long and Winding Road > > To: [EMAIL PROTECTED] > > Sent: Tuesday, March 04, 2003 11:04 PM > > Subject: Off Topic - just screwing around and what do I > see? [7:64449] > > > > > > three routers in a circle. but that's irrelevant. > > > > inbound from r3-------r1--r2-----r3----->back to r1 > > > > > > I have IGRP between two of the routers. I have loopback on > each of the > two > > routers -- 222.222.222.x/32 > > > > watching the 222.222.222.0/24 subnet advertisement. R2 > sends it to R3 > and > > R3 > > sends it to R2 > > > > ??????????????????????????? > > > > wait a minute - since when does EIGRP automatically > redistribute into > IGRP, > > even when the AS numbers are DIFFERENT???????? > > > > router eigrp 200 > > passive-interface default > > no passive-interface Serial1 > > network 199.35.1.0 > > network 222.222.222.0 > > no auto-summary > > no eigrp log-neighbor-changes > > ! > > router igrp 100 > > passive-interface default > > no passive-interface Serial0 > > network 199.34.1.0 > > ! > > Router_3#sh ip route 222.222.222.0 > > Routing entry for 222.222.222.0/24, 2 known subnets > > Attached (1 connections) > > Variably subnetted with 2 masks > > Redistributing via eigrp 200 > > Advertised by igrp 100 > > > > ???????????????? > > > > well, at least IGRP isn't in the Lab any longer...... > > > > -- > > TANSTAAFL > > "there ain't no such thing as a free lunch" > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64541&t=64478 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
