>I have been trying to follow this, and I still do not see why we should >get away from the old Cisco switch courses that if you set both sides to >100 full duplex if they are capable you will be fine. I have not seen >any situation where hard setting both sides caused problems (am I >missing something?). Question I ask is why even fool with the >unpredictable auto negotiate. > >Someone help me out here what am I missing.
The problem that you will eventually run into is that there is no standard behavior specified except for autonegotiation. Since we installed over thirty Catalyst 2950s, several 2948Gs, a few 2980Gs, and a 6513 I've started seeing this issue. If you manually set the speed and duplex that results in one of two possible behaviors, neither of which is specified in any standard. Read my explanation below again where I describe the two options. If you start mixing one set of products that picks option #1 with another set that chooses option #2 I guarantee you will see problems and it will drive you crazy. :-) It appears that older Cisco switches utilized option #1, as do the majority of the NICs that we use. When we switched to the newer Cisco switches an avalanche of troubleshooting began, along with our support team being flooded with calls. They usually went something like this: "Someone from your department was replacing something in the back room this morning and now everything runs terribly slow." Ugh.... we must have heard that at least forty times, and just here at our headquarters it seems like we're resolving user and server issues daily by setting the NICs and switches to auto. If hard setting everything is currently working for you, don't change a thing. Just be aware of the issue because it's bound to sneak up on you sooner or later. John > >-----Original Message----- >From: John Neiberger [mailto:[EMAIL PROTECTED] >Sent: Monday, March 10, 2003 2:59 PM >To: [EMAIL PROTECTED] >Subject: Re: 10 half or 100 full [7:64931] > >The problem is that neither behavior is proper! :-) The only method >mentioned in the standard is autonegotiation. Any other setting, >including >manually setting the speed and duplex, is non-standard and undefined. > >I'm not aware of the frame-level details of Nway negotiation so I'm not >sure >what you'd need specifically to see the traffic but it would probably >have >to be some sort of transparent device that sits between the NIC and the >switch. > >>>> Scott Roberts 3/10/03 12:31:46 PM >>> >I see what you're saying now. what would be nice to see is what traffic >there is on a protocol analyzer. I would think that #2 should be the >situation and your #1 is not the proper negotiation. > >I've never tried to cpature auttonegotiation with an analyzer before, I >wonder if you can even capture that stuff? > >scott > >""John Neiberger"" wrote in message >news:[EMAIL PROTECTED] >> No, that's not at all what I was referring to. I'm speaking of the >behavior >> of switch interfaces when they're set to AUTO. Nortel switches (at >least >> the ones that we used) and some older Cisco switches like the 2924XL >seemed >> to behave like Option #1 below, while the 2950 behaves like Option #2. >> >> If both the switch and the device are using Option #1 you'll be fine. >If >you >> then upgrade to a Catalyst 2950 that uses Option #2, you'll have all >sorts >> of issues that need to be resolved. >> >> We've had a mixture of 2924XL and Bay 303/310 switches at our branchse >for >> quite a while with no issues. When we started replacing the Bays with >> Catalyst 2950s we started having all sorts of problems, and it took >quite >a >> bit of research into FastEthernet NWAY/Autonegotiation to determine >the >> problem. >> >> Just a forewarning. :-) >> >> >>> Scott Roberts 3/10/03 12:12:48 PM >>> >> if I understand what you're saying, I think its always been like that, >cisco >> hasn't changed it. >> >> you're refering to the fact that the IOS switch don't let you change >the >> speed? I think thats strange also, the set based switch can allow you >to >> change speed, but after the IOS "upgrading" of switches they don't >allow >you >> to change a 10/100 at the switch, but rather require you to configure >the >> desktop to 10 or 100 speed manually. >> >> I suppose the idea is that everyone should be using autonegotiation >> according to cisco. >> >> scott >> >> ""John Neiberger"" wrote in message >> news:[EMAIL PROTECTED] >> > I wanted to mention that we've been in the process of upgrading our >> > switches, as well, and I discovered that since we've started using >the >new >> > Cisco switches we've been having all sorts of problems getting the >speed >> and >> > duplex settings set correctly. >> > >> > We've discovered that if you have relatively new NICs with updated >> drivers, >> > set both sides to AUTO. Never, ever, set only one side to AUTO. I'd >also >> > avoid manually configuring the speed and duplex unless you have to >do so >> to >> > fix a specific problem. Here's why: >> > >> > There is no standardized behavior for 100BaseTX when you manually >> configure >> > settings! The only setting mentioned in the specification is AUTO; >the >> > behavior of the NIC with any other setting is up to the vendor and >not >> > everyone handles it the same way. Cisco appears to have changed the >way >> > they handle it, which is the cause of a lot of our problems. >> > >> > If you hard-set the speed and duplex there are two ways to handle >this: >> > >> > 1. Use the configured settings and still participate in >autonegotiation >> > only offering the configured settings. >> > >> > 2. Use the configured settings and do not participate in >autonegotiation >> > >> > Cisco's new switches seem to use option #2, while a great number of >our >> end >> > devices use option #1. Why is this a problem? Here's what happens >when >> you >> > connection an option #1 device to an option #2 device: >> > >> > #1 participates in autonegotiation, only offer the configured >settings. >> > #2 does not participate in autonegotiation at all and will >forcefully >use >> > the configured settings. >> > #1, seeing that there's nothing on the other side using auto assumes >it >is >> > connected to a HUB, and just might set itself to 10/Half regardless >of >the >> > manually configured settings! >> > >> > As you can guess, this is bad mojo. The moral of the story is that >you >> > should try to start using AUTO on BOTH sides if you're using newer >Cisco >> > switches, in particular the 2950 series. In some cases this won't >work >> and >> > you'll have to resort to manual settings. >> > >> > HTH, >> > John Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64987&t=64931 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
