Another strange routing behaviour
Hi, all. I might have posted something similar to this not too long ago but I might not have beed specific enough. Here's the story: HostA ---Router1---Router9HostB If i traceroute from within Router1 to HostB, it goes through. But if i do the same from HostA, it stops at Router9. The same thing happens when tracerouting from HostB's end, it stops at Router1. So i checked with another network that also has a route to Router9, ans the same story happens. From the Router-Y the trace gets to HostB. But from Host-Y it stops at Router9. Has anyone else seen this and figured out the cause? Thanks. Elmer Deloso _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Another strange routing behaviour
This sounds like an access list problem somewhere. It could be on Router9, or it could be on the other routers. Outgoing access lists do not filter packets originated from the routers themselves. So, you could have an access list blocking outgoing ICMP that would still allow the router itself to originate a trace but would block any other hosts from doing the same thing. Or, perhaps you have an access list on Router9 that is blocking ICMP from other networks, but not directly attached networks/routers. I would initially take the following steps: Telnet to router9, turn off logging to the console and turn on icmp debugging. Try a trace from Router1 and then one from HostA. Turn off debugging and examine the logs. (assuming that you were logging in the first place.) Then go to Router1 and repeat the process. That might help pinpoint where the problem actually lies. HTH, John >>> "Deloso, Elmer G (WPNSTA Yorktown)" <[EMAIL PROTECTED]> 2/16/01 9:03:32 AM >>> Hi, all. I might have posted something similar to this not too long ago but I might not have beed specific enough. Here's the story: HostA ---Router1---Router9HostB If i traceroute from within Router1 to HostB, it goes through. But if i do the same from HostA, it stops at Router9. The same thing happens when tracerouting from HostB's end, it stops at Router1. So i checked with another network that also has a route to Router9, ans the same story happens. From the Router-Y the trace gets to HostB. But from Host-Y it stops at Router9. Has anyone else seen this and figured out the cause? Thanks. Elmer Deloso _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Another strange routing behaviour
Hello, From personal experience I would point the finger at access lists. Take this scenario into account Host A -> RouterA -> (wan) -> RouterB -> HostB 192.168.1.0 192.168.2.0 192.168.3.0 Ok, if you had an access list that say permitted traffic to exit on Router A from Router B it would get to HostA, BUT that same access list would not permit HostB on a different subnet to Talk to Host A. That would require RouterA to know about Host B's subnet and allow routing from it. The same holds true crossing the link in the opposite direction. Brandon Ripper CCNA PS This would happen on the entire net because off same config problem every place, or possibly lack of config. At 11:03 AM 2/16/01 -0500, you wrote: >Hi, all. >I might have posted something similar to this not too long ago but I might >not have beed specific enough. Here's the story: > >HostA ---Router1---Router9HostB > >If i traceroute from within Router1 to HostB, it goes through. >But if i do the same from HostA, it stops at Router9. >The same thing happens when tracerouting from HostB's end, it stops >at Router1. >So i checked with another network that also has a route to Router9, >ans the same story happens. From the Router-Y the trace gets to >HostB. But from Host-Y it stops at Router9. >Has anyone else seen this and figured out the cause? >Thanks. > >Elmer Deloso > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Another strange routing behaviour
--- "Deloso, Elmer G (WPNSTA Yorktown)" <[EMAIL PROTECTED]> wrote: > Hi, all. > I might have posted something similar to this not too long ago but I > might > not have beed specific enough. Here's the story: > > HostA ---Router1---Router9HostB > > If i traceroute from within Router1 to HostB, it goes through. Which leads me to believe Router 9 is not filtering high UDP packets, ICMP Time Exceeded, or ICMP Destination Port Unreachable. > But if i do the same from HostA, it stops at Router9. Router 9 may be filtering ICMP echo reply packets. (Echo request packets go through because Host B's traceroute stops at Router 1 not at 9.) A Windows host uses ICMP Echo (instead of high port UDP) packets when using "tracert". Everyone else traceroutes normally. > The same thing happens when tracerouting from HostB's end, it stops > at Router1. I wonder if it's the access-lists? > So i checked with another network that also has a route to Router9, > ans the same story happens. From the Router-Y the trace gets to > HostB. But from Host-Y it stops at Router9. > Has anyone else seen this and figured out the cause? Check if "ping" from the routers to each of the hosts works. __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail - only $35 a year! http://personal.mail.yahoo.com/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
