"the split horizon rule prohibits a router from advertising a route through an interface that the router itself uses to reach the destination."
So in my scenario router 0 is learning a route via fa0/1 an router 2 when the same subnet is learnt from router 1 on fa0/0. This would exlain it, but I do see a routing update reach router 2 for this subnet in a debug ip eigrp. This must be the problem, but I don't think I can fix it. Don't want to turn off split horizon in the eigrp domain.. Time for a rethink Sent from my iPhone On 9 Mar 2010, at 10:27, Mark Beynon <[email protected]> wrote: > Okay, I have disabled split horizon on the interfaces between r0 and > r2. > > It now works > > I need to understand what is going on here. > > I thought split horizon would stop a router sending an update out the > interface it received it on. > > In this case these are routes originating from different sources, but > for the same subnet,.. ? > > Sent from my iPhone > > On 9 Mar 2010, at 10:11, Mark Beynon <[email protected]> wrote: > >> The whole scenario is based around providing resillience. Hence why >> the route is redistributed at both r1 and r2. In production r0 >> represents a eigrp domain who need to learn the routes. >> >> The intention is that as soon r1 redistributes the static, r2 should >> hear it, and place it in it's route table due to better ad. Removing >> the static. >> >> However, you are correct, if I don't redistribute the static at r2 >> the >> failover an fail back works fine. >> >> Doesn't solve my problem however. >> >> Why is the redistribution stopping this? >> >> >> >> Sent from my iPhone >> >> On 9 Mar 2010, at 09:50, Markku Leiniö <[email protected]> wro >> te: >> >>> Hi, on R2 you are redistributing the static route (45.45.45.45/32) >>> to >>> EIGRP. Could that be the reason for this issue? >>> >>> Markku >>> >>> >>> On Tue, Mar 9, 2010 at 11:28 AM, Mark Beynon <[email protected]> >>> wrote: >>>> >>>> I have now reproduced this from scratch, using different router >>>> models in >>>> GNS3. As mentioned before this works fine in OSPF, but does not >>>> work in >>>> EIGRP. >>>> >>>> i have removed all complications, and i am now simply >>>> redistributing a >>>> static route to null0 on one side of the network. At the other, a >>>> floating >>>> static route to the same address via null0 with an AD of 210. >>>> >>>> when the remote route is removed, the floating static enters the >>>> routing >>>> table. when it is re-added remotely, the floating static is not >>>> removed. >>>> >>>> Heres the weird thing. >>>> >>>> If i do this on a chain of two routers, it works perfectly. >>>> if i extend the chain to three routers, it doesn't. >>>> >>>> configs pasted. R1 left hand router where routes are added and >>>> removed. >>>> R0 middle router. >>>> R2 left hand router with floating static. >>>> >>>> >>>> just in case any one can reproduce for me.. :) >>>> >>>> thanks >>>> >>>> config >>>> >>>> ! >>>> version 12.4 >>>> service timestamps debug datetime msec >>>> service timestamps log datetime msec >>>> no service password-encryption >>>> ! >>>> hostname R1 >>>> ! >>>> boot-start-marker >>>> boot-end-marker >>>> ! >>>> ! >>>> no aaa new-model >>>> memory-size iomem 15 >>>> ip cef >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> interface FastEthernet0/0 >>>> ip address 10.10.10.10 255.255.255.0 >>>> duplex auto >>>> speed auto >>>> ! >>>> interface FastEthernet0/1 >>>> no ip address >>>> shutdown >>>> duplex auto >>>> speed auto >>>> ! >>>> router eigrp 1 >>>> redistribute static >>>> network 10.10.10.0 0.0.0.255 >>>> no auto-summary >>>> ! >>>> ip forward-protocol nd >>>> ip route 45.45.45.45 255.255.255.255 Null0 >>>> ! >>>> ip http server >>>> no ip http secure-server >>>> ! >>>> ! >>>> control-plane >>>> ! >>>> ! >>>> line con 0 >>>> line aux 0 >>>> line vty 0 4 >>>> login >>>> ! >>>> ! >>>> end >>>> >>>> >>>> >>>> >>>> ! >>>> version 12.4 >>>> service timestamps debug datetime msec >>>> service timestamps log datetime msec >>>> no service password-encryption >>>> ! >>>> hostname R0 >>>> ! >>>> boot-start-marker >>>> boot-end-marker >>>> ! >>>> ! >>>> no aaa new-model >>>> memory-size iomem 15 >>>> ip cef >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> interface FastEthernet0/0 >>>> ip address 10.10.10.1 255.255.255.0 >>>> duplex auto >>>> speed auto >>>> ! >>>> interface FastEthernet0/1 >>>> ip address 20.20.20.2 255.255.255.0 >>>> duplex auto >>>> speed auto >>>> ! >>>> router eigrp 1 >>>> redistribute static >>>> network 10.10.10.0 0.0.0.255 >>>> network 20.20.20.0 0.0.0.255 >>>> no auto-summary >>>> ! >>>> ip forward-protocol nd >>>> ip route 55.55.55.55 255.255.255.255 Null0 >>>> ! >>>> ip http server >>>> no ip http secure-server >>>> ! >>>> ! >>>> control-plane >>>> ! >>>> ! >>>> line con 0 >>>> line aux 0 >>>> line vty 0 4 >>>> login >>>> ! >>>> ! >>>> end >>>> >>>> >>>> ! >>>> version 12.4 >>>> service timestamps debug datetime msec >>>> service timestamps log datetime msec >>>> no service password-encryption >>>> ! >>>> hostname R2 >>>> ! >>>> boot-start-marker >>>> boot-end-marker >>>> ! >>>> ! >>>> no aaa new-model >>>> memory-size iomem 15 >>>> ip cef >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> ! >>>> interface FastEthernet0/0 >>>> ip address 20.20.20.20 255.255.255.0 >>>> duplex auto >>>> speed auto >>>> ! >>>> interface FastEthernet0/1 >>>> no ip address >>>> shutdown >>>> duplex auto >>>> speed auto >>>> ! >>>> router eigrp 1 >>>> redistribute static >>>> network 20.20.20.0 0.0.0.255 >>>> no auto-summary >>>> ! >>>> ip forward-protocol nd >>>> ip route 45.45.45.45 255.255.255.255 Null0 210 >>>> ip route 55.55.55.55 255.255.255.255 Null0 210 >>>> ! >>>> ip http server >>>> no ip http secure-server >>>> ! >>>> ! >>>> control-plane >>>> ! >>>> ! >>>> line con 0 >>>> line aux 0 >>>> line vty 0 4 >>>> login >>>> ! >>>> ! >>>> end >>>> >>>> _______________________________________________ >>>> For more information regarding industry leading CCIE Lab training, >>>> please >>>> visit www.ipexpert.com >>>> >>>> >>> >>> >>> >>> -- >>> Markku >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, >> please visit www.ipexpert.com > _______________________________________________ > For more information regarding industry leading CCIE Lab training, > please visit www.ipexpert.com _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
