nice catch daniel, I've never used that before, will be mulling this one over in my lab for the next week.
learn something new everyday, scott ""Daniel Cotts"" wrote in message news:[EMAIL PROTECTED] > standby track (interface) might do the trick. > http://www.cisco.com/warp/public/619/6.html > I've never seen HSRP on both sides of a router. Maybe each side could track > the ethernet interface on the other side. If the far side goes down then the > monitoring side decrements its priority and allows the other router to take > over. > > > -----Original Message----- > > From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED] > > Sent: Thursday, March 06, 2003 6:52 PM > > To: [EMAIL PROTECTED] > > Subject: Re: it started out as a really good idea ... [7:64638] > > > > > > Larry Letterman wrote: > > > > > > that was my answer as well...the broken connection will black > > > hole the path on > > > one side or the other... > > > > > > Larry Letterman > > > Network Engineer > > > Cisco Systems > > > > Whew! I wasn't losing it. :-) > > > > For this to work, you would need a way to tell Router 1 (as > > well as Router > > 2), "if my E0 interface goes down, make sure I'm not the > > default gateway on > > my E1 interface." (And vice versa.) > > > > Maybe you can do that with HSRP? I don't know how though. > > > > HSRP does have an advanced feature to avoid LAN users using a default > > gateway that has lost its access to the "rest of the network" > > on its other > > interface. I can't remember how to do that, but it's > > supported somehow, from > > what I understand. But I don't think that helps. It's not the > > same as no > > longer being the default gateway for the LAN that reaches the > > "rest of the > > network" because you're no longer the default gateway on the > > local LAN. > > > > Sorry if that's convoluted. I can't think of a better way of > > saying it! ;-) > > > > I think a routing protocol solves the problem too, but there are some > > gotchas. > > > > Assuming I understand his topology correctly, with a > > distance-vector routing > > protocol, Router 2 would not send via its E0 interface a > > route that tells > > Router 1 that Router 2 can get to network 10.3.0.0, due to > > split horizon. > > That's fine. > > > > However, Router 2 would tell Router 1 this information via > > its E1 interface. > > > > When there's no problem, Router 1 would ingore this > > information because > > Router 1 can get to network 10.3.0.0 directly already. > > > > Now Router 1's E0 goes down. After the route comes out of > > holdown (could be > > a long time for some routing protocols) Router 1 will accept > > Router 2's > > offer to send to network 10.3.0.0. > > > > Now, it gets a little hairy..... > > > > Packet comes in on Router 1's E1 interface destinated to > > 10.3.x.x. (That's > > the ping reply from PC 2 to PC1.) Router 1 should send the > > packet back out > > E1 and let Router 2 pick it up. Router 1 may send an ICMP > > redirect too, > > which would avoid the extra hop in the future, except that > > ICMP redirects > > are often disabled with HSRP. > > > > I think that would work? It's not too pretty, but that's OK, > > he said it was > > a lab network. :-) > > > > I think the general-purpose answer is that the original > > poster did sort of > > misunderstand HSRP's purpose. In a hierarchical network > > design, you probably > > wouldn't have a router that was a default gateway on both sides of it. > > > > Instead, you might have two routers on a LAN acting together > > (with HSRP) as > > the default gateway. Both these routers can also get out to > > the rest of the > > network, for example the rest of the enterprise network or > > the Internet, so > > it doesn't matter which one gets used. > > > > Priscilla > > > > > > > > > > > ----- Original Message ----- > > > From: Priscilla Oppenheimer > > > To: [EMAIL PROTECTED] > > > Sent: Thursday, March 06, 2003 3:23 PM > > > Subject: Re: it started out as a really good idea ... > > > [7:64638] > > > > > > > > > Um, he already has both the E0s in the same subnet and both > > > the E1s in the > > > same subnet, according to his config. > > > > > > His drawing is confusing but I think he's got PC1 and both > > > E0s in subnet > > > 10.3.0.0/16, say on a hub or a switch. > > > > > > He's got PC2 and both E1s in subnet 10.4.0.0, on another hub > > > or switch. > > > > > > If the problem isn't related to misconfiguration of the > > > default gateway on > > > the PCs, I do have another theory. :-) > > > > > > Say he pulls the E0 cable on Router 1. No problem, PC1 will > > > start using > > > Router2. > > > > > > Then he pings from PC1 to PC2. The ping will probably get > > > there but what > > > about the reply coming back? > > > > > > What happens if PC2 is using Router 1 and Router 1 has no way > > > to send PC2's > > > packet from itself to Router 2 due to the missing cable, not > > > to mention > > > lack > > > of any routing protocol configured. > > > > > > Think about it! :-) > > > > > > Priscilla > > > > > > The Long and Winding Road wrote: > > > > > > > > ""garrett allen"" wrote in message > > > > news:[EMAIL PROTECTED] > > > > > i have a need for a high availability solution for a > > > default > > > > gateway > > > > > configuration. just finished the ccdp and thought it > > > might be > > > > > interesting to try hsrp on a pair of 2514's. put some of > > > > that theory > > > > > to work. instead of highly resiliant i've managed to > > > > configure it for > > > > > mass failure. arg.., not exactly what i had in mind. > > > now, > > > > any time i > > > > > take down 1 of the 4 links, the connect between 2 remote > > > > hosts dies. > > > > > this is in a lab (production is not a lab, production is > > > not > > > > a lab...) > > > > > so it is a mystery i would like to solve, but it is not > > > > critical. > > > > > > > > > > here is the basic config (hope it makes it): > > > > > > > > > > pc host 1 -----+----- e0 router 1, e1 ----+--------- pc > > > > host 2 > > > > > | | > > > > > |----- e0 router 2, e1 ----| > > > > > > > > > > the routers act as a default gateway between the internal > > > > network > > > > > (represented by pc host 1) and the external world > > > > (represented by pc > > > > > host 2). i have used 10.3 and 10.4 /16 as the addresses > > > for > > > > each side > > > > > of the divide. i want to run hsrp on both sets of router > > > > interfaces so > > > > > that in the event a router or an interface fails, the > > > traffic > > > > impact is > > > > > minimized. in the real world pc host 2 will be a firewall > > > > and there > > > > > will be other hosts off that segment as well > > > > > > > > > > looks easy. sounds plausible. read the cisco docs. > > > looks > > > > like it > > > > > should work. minimal incantations before tickling the > > > > keyboard. key > > > > > in the configs and it fires up nicely. do the show standby > > > > thingee and > > > > > all looks cool. can ping the 2 stations end to end. most > > > > excellent. > > > > > put a router in debug mode. when i pull one of the 4 > > > router > > > > cables the > > > > > router goes through a state change but no bits make it to > > > the > > > > far end. > > > > > not even the shiney ones. bitstream courtesy of ping. > > > > > > > > > > maybe i misunderstood what hsrp was suppose to do. the > > > > configs are > > > > > below, along with the show standby results. both are > > > 2514's > > > > (2 aui's) > > > > > and both are running 12.2(1d). probably forgot to put the > > > > interface in > > > > > mumble mode or something equally easy. no laughter, > > > please. > > > > > > > > > > > > HSRP assumes the ehternet interfaces to be on the same > > > subnet. > > > > your ehternet > > > > side is on two different subnets. hence - no failover. > > > > > > > > to get this to work using 2514's: > > > > > > > > > > > > E0----------2514_1-----------E1 > > > > > > > > E0----------2514_2-----------E1 > > > > > > > > > > > > the e0's on the same subnet, the e1's on the same subnet > > > > > > > > > > > > > > > > > > > > > > > > > > thanks in advance. > > > > > > > > > > router 1 > > > > > interface Ethernet0 > > > > > ip address 10.3.255.2 255.255.0.0 > > > > > no ip route-cache > > > > > no ip mroute-cache > > > > > standby 1 priority 200 preempt > > > > > standby 1 ip 10.3.0.2 > > > > > ! > > > > > interface Ethernet1 > > > > > ip address 10.4.254.2 255.255.0.0 > > > > > no ip route-cache > > > > > no ip mroute-cache > > > > > standby 2 priority 200 preempt > > > > > standby 2 ip 10.4.254.10 > > > > > > > > > > > > > > > router 2 > > > > > interface Ethernet0 > > > > > ip address 10.3.255.1 255.255.0.0 > > > > > no ip route-cache > > > > > no ip mroute-cache > > > > > standby 1 priority 225 preempt > > > > > standby 1 ip 10.3.0.2 > > > > > ! > > > > > interface Ethernet1 > > > > > ip address 10.4.254.1 255.255.0.0 > > > > > no ip route-cache > > > > > no ip mroute-cache > > > > > standby 2 priority 150 preempt > > > > > standby 2 ip 10.4.254.10 > > > > > > > > > > results of show standby > > > > > Router1#show standby > > > > > Ethernet0 - Group 1 > > > > > Local state is Standby, priority 200, may preempt > > > > > Hellotime 3 holdtime 10 > > > > > Next hello sent in 00:00:00.940 > > > > > Hot standby IP address is 10.3.0.2 configured > > > > > Active router is 10.3.255.1 expires in 00:00:09, > > > priority > > > > 225 > > > > > Standby router is local > > > > > 20 state changes, last state change 00:22:34 > > > > > Ethernet1 - Group 2 > > > > > Local state is Active, priority 200, may preempt > > > > > Hellotime 3 holdtime 10 > > > > > Next hello sent in 00:00:01.676 > > > > > Hot standby IP address is 10.4.254.10 configured > > > > > Active router is local > > > > > Standby router is 10.4.254.1 expires in 00:00:08 > > > > > Standby virtual mac address is 0000.0c07.ac02 > > > > > 17 state changes, last state change 00:23:26 > > > > > Router1# > > > > > > > > > > Router2#show standby > > > > > Ethernet0 - Group 1 > > > > > Local state is Active, priority 225, may preempt > > > > > Hellotime 3 holdtime 10 > > > > > Next hello sent in 00:00:01.010 > > > > > Hot standby IP address is 10.3.0.2 configured > > > > > Active router is local > > > > > Standby router is 10.3.255.2 expires in 00:00:09 > > > > > Standby virtual mac address is 0000.0c07.ac01 > > > > > 24 state changes, last state change 00:22:04 > > > > > Ethernet1 - Group 2 > > > > > Local state is Standby, priority 150, may preempt > > > > > Hellotime 3 holdtime 10 > > > > > Next hello sent in 00:00:01.272 > > > > > Hot standby IP address is 10.4.254.10 configured > > > > > Active router is 10.4.254.2 expires in 00:00:09, > > > priority > > > > 200 > > > > > Standby router is local > > > > > 32 state changes, last state change 00:22:25 > > > > > Router2# Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64750&t=64638 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
