DHCP problems

[tiwang]

Hi folks

We have discovered an evolving problem. Our customers - normally small sites with 5 - 25 PC's get their IP config from an DHCP server in an Cisco SOHO router - typically an 831 with IOS 12.2(8) or similary. We also often have an Cisco Catalyst switch (CAT 2950) in there. The clients - Windows 9x, Windows 2kPro & XP Pro from time to time boots without an DHCP assigned IP - hereby booting with an 169.x.y.z address and those problems which this can initiate for a normal PC User!.

Is this an know issue when using the DHCP service in these SOHO routers - or - help - what can be done - any suggestions?? I expect the cause for these problems are either dropped packets so that the Cisco router newer receives an DHCP request - or it is to slow to process them (hmm - for 5 - 25 clients - doesnt make sense) Any suggestions for tracing - debugging or alternate configs??

Kind Regards

Thomas Iwang

[thisisshanky]

Use a sniffer such as Ethereal to decode dhcp requests, discover, reply packets back and forth between the PC and see if you can find any issues.

(www.ethereal.com)

[xepherys]

Is this happening only at one site or does this happen with many clietns at different locations?

If this is only one site, it's possible that there are physical issues. Perhaps bad cabling? Are there any hubs installed or are all devices connected directly to the 2950? Are there more than one switch? If so, are all the failed requests coming from one switch?

If this is multiple sites, you may want to open a TAC case. Perhaps there is an IOS issue involved.

[tiwang]

This is happening at several sites. I am trying to get an overview of which components are involved in all cases - because if it is only occuring onsites where we have an switch involved then it could of course be the "portfast" setup on the switch which is causing this.

[glen.grant]

Do you have portfast turned on for the 2950 user ports , this would prevent the users from getting an address if it's not .