[c-nsp] Embeded Packet Capture for DHCP Troubleshooting

[Jeff Wojciechowski]

2801 is doing dhcp - and I wanted to get a packet capture to see why 2 thin clients won't get dhcp leases successfully from the 2801 upon boot up (so before the client has an ip from dhcp - isn't the dhcp transaction all arp?)


Sent from Midland Paper Company's Blackberry Server

From: Heath Jones [mailto:hj1980 at gmail.com]
Sent: Tuesday, September 21, 2010 10:12 AM
To: Jeff Wojciechowski
Cc: cisco-nsp at puck.nether.net <cisco-nsp at puck.nether.net>
Subject: Re: [c-nsp] Embeded Packet Capture for DHCP Troubleshooting

I just re-read and saw it was the 2601 as the dhcp server.

What problem are you trying to solve?

On 21 September 2010 16:10, Heath Jones <hj1980 at gmail.com<mailto:hj1980 at gmail.com>> wrote:
Hi Jeff - which device is performing the dhcp server function and what problem are you actually having?



On 21 September 2010 15:46, Jeff Wojciechowski <Jeff.Wojciechowski at midlandpaper.com<mailto:Jeff.Wojciechowski at midlandpaper.com>> wrote:
All:

I would like to use Embedded Packet Capture at a remote site to troubleshoot IOS DHCP at a remote site.

(referencing http://www.cisco.com/en/US/docs/ios/netmgmt/configuration/guide/nm_packet_capture_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1060070)

The concept looks pretty straightforward but since DHCP negotiation isn't IP - I am having trouble with building the access list to determine what traffic to capture.

The device I would like to perform the capture on is a 2801 and that is the device serving DHCP to clients at that site.

Utilization on that router is pretty low so if I *had* to capture all traffic on F0/0 and dump it via TFTP to the fileserver at the site - I think that might be a viable option? But the fileserver is connected to the switch that connected to F0/0 that I want to perform the capture on.

Regular DHCP debugs only show that 2 devices are continually offered IPs but then apparently keep re-requesting them. (So maybe I am barking up the wrong tree here.)

Diagram:

WAN----Serial-2801-F0/0----Switch------DHCP Clients and Fileserver

Any and all hints would be greatly appreciated.

Thanks much,

Jeff Wojciechowski
LAN, WAN and Telephony Administrator
Midland Paper Company
101 E Palatine Rd
Wheeling, IL 60090
* tel: 847.777.2829
* fax: 847.403.6829
e-mail: jeff.wojciechowski at midlandpaper.com<mailto:jeff.wojciechowski at midlandpaper.com><mailto:jeff.wojciechowski at midlandpaper.com<mailto:jeff.wojciechowski at midlandpaper.com>>
http://www.midlandpaper.com<http://www.midlandpaper.com/>




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