I know what you mean Chuck, it's hard to explain a misconfigured network. Not implying the Ole misconfigured the router per se but when auto stuff doesn't work that is the end result. I have been involved numerous times in problems that were auto related but most often things "work" but performance is degraded and inconsistant which can lead you down other paths!!
Bottom line, if you can avoid it don't trust auto, hardcode the speeds and duplex whenevr possible!!!!! Dave Chuck Larrieu wrote: > > An interesting read, particularly since I am reviewing Kennedy clark's cisco > Lan Switching book prior to reviewing Cat5K and Cat 3920 configuration. > > I am somewhat surprised at both the phenomenon and the concludion. Spanning > tree blocks for particular reasons. > > when you concluded that your configurations were identical at all offices, > does that mean that your port negotiations were set to auto everywhere else? > both on the routers and on the local switches? if so, I would expect to see > similar problems elsewhere. > > is it possible that there was a duplicate mac someplace in another part of > the bridged network, one that was being picked up by STP and interpreted as > a loop? You mention changing macs of interfaces as part of your > experimentation. Are you certain that this process was not part of the > solution? > > To be frank, I'm hard pressed to come up with a reason why the FE port on > the router would go into blocking. I can see that hapening on the serial > port for reasons that have been discussed on this group in the past. I can't > come up with a rationale as to why hard setting of speed and duplex would > make a difference. I suppose one MIGHT conclude that if the port is in full > duplex, the STP process MIGHT see a loop occuring over the two different > wire pairs. that's about the only wild rationale I can come up with. And > that one is really stretching the point / bug / whatever. > > In any case, thanks for the good read. > > Chuck > > ""Ole Drews Jensen"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > After a fun evening last night, I have decided not to trust the > autosensing > > on ethernet interfaces anymore. > > > > I was at a branch office where the users could not access the corporate > > network. The router, a 1720 setup as a bridge with the same IP address for > > the FastEthernet as the Serial subinterface, both configured for > > bridge-group 1. It was connected to a 2620 at the corporate office via a > > Fractional Frame Relay connection. > > > > I changed the switch out with an old spare hub I had lying around, and > > connected only one workstation from the local network. After starting the > > router up, I could ping the local workstation, and I could ping devices on > > the corporate network, so both my FastEthernet and Serial interfaces were > > working fine. However, I could not ping anything on the corporate network > > from my workstation, nor could I from a telnet connection to my corporate > > router ping the workstation, so traffic was not being passed through > between > > the interfaces. > > > > That looked like a typical routing problem, but the only problem was that > I > > was not routing, I was bridging, so ????? > > > > I did a "show bridge 1 group" and saw that the FastEthernet was in a > > blocking state by the spanning tree, so something was wrong here. I > cleared > > the arp table on the router and on all other routers and switches. I tried > > to assign a different mac address to the FE interface. I tried a different > > workstation. No matter what I did, it kept being in a blocking state. > > > > I went in and did a "bridge-group 1 spanning-disabled" on the interface, > and > > it changed to forwarding state, but I could still not pass traffic > through. > > > > This is when I called TAC, but after I guided them through to a telnet > > connection to my routers, they decided after three hours that something > > weird was going on with the router, and they did an RMA for a replacement > > unit. > > > > However, I decided to continue my troubleshooting, because I hate to give > > up. I reconfigured everything, I tried to create a bridge-group 2 instead, > I > > forced it into IP routing, and back off it again, but no matter what, it > > kept going into blocking mode (I had removed the spanning-disabled command > > again at that time). > > > > That's when it hit me to try and force the speed on the interface. It was > in > > AUTO, and my switch had been auto 10/100, but my hub was only 10. I > changed > > it from auto to 10 and power cycled the router. PLING!!! Now it started up > > and after the listening and learning, it went in forwarding state, and I > > could now ping through my router, and I could connect my workstation to > the > > corporate network. > > > > What makes this strange is that I can apparently use my FastEthernet > > interface from the router even though the speed is wrong, but the STP > see's > > this and blocks the interface for switched traffic. WEIRD!!!!! > > > > Read the entire case study here: > > > > http://www.RouterChief.com/CaseStudies/1.htm > > > > Ole > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Ole Drews Jensen > > Systems Network Manager > > CCNP, MCSE, MCP+I > > RWR Enterprises, Inc. > > [EMAIL PROTECTED] > > http://www.RouterChief.com > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > NEED A JOB ??? > > http://www.oledrews.com/job > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 "Emotion should reflect reason not guide it" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30533&t=30446 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
