It's been more than once when I've encountered autonegotiation/autosense issues between a Cisco router and Cisco switch. I've even seen problems when both interfaces were 10/100 and both hard-coded to 100/full and the link wouldn't come up. This may a chink in the Cisco armor as I rarely encounter issues with autonegotiation/autosense with other equipment but when I install a new Cisco network, one thing I ALWAYS have to do is go through the 10/100 ports of every switch and look for duplex (and sometimes speed) mismatches. Crazy...
Rik -----Original Message----- From: Kane, Christopher A. [mailto:[EMAIL PROTECTED]] Sent: Saturday, December 29, 2001 11:02 PM To: [EMAIL PROTECTED] Subject: RE: Autosense this ... (add to your knowledgebase) [7:30446] It's unfortunate that sometimes when things break, they don't perform in expected ways. Rather it truly was an Autosense problem or not, who knows. But it brings up a chance to talk about Autosense. I've had it bite me more than once. I've had problems with Autosense that didn't show up until months after installation. It doesn't matter if its Cisco to Cisco or Cisco to another vendor, I've had to lock down ports at certain speeds and modes to solve problems on several occasions. Just to pass along some experience, you may always be better off hard setting your options. Nice persistence Mr. Jensen, it's cool to stick with something until you can make it work. Chris -----Original Message----- From: Chuck Larrieu [mailto:[EMAIL PROTECTED]] Sent: Saturday, December 29, 2001 6:14 PM To: [EMAIL PROTECTED] Subject: Re: Autosense this ... (add to your knowledgebase) [7:30446] 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 > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30537&t=30446 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
