[c-nsp] Embeded Packet Capture for DHCP Troubleshooting

[Heath Jones]

Well I think your on the right track with the packet capture then.
It looks as if the client either never sees the dhcp proposal, or the
proposal itself is unacceptable to the client. (there are more
potential issues, but only when there is more than 1 dhcp server)

so for the access list:
access-list 100 permit udp any any eq bootps
access-list 100 permit udp any any eq bootpc

as a good comparison, you can use working dhcp packet captures on the
net (search for wireshark sample captures).

cheers




On 21 September 2010 16:58, Jeff Wojciechowski
<Jeff.Wojciechowski at midlandpaper.com> wrote:
> Nope - got a cat3560 doing nothing at all really - just one vlan - no qos - nothing crazy at all.
>
> Clients aren't locked down either (even had the terminals set to factory defaults with DHCP)
>
>  And from the switch side - no errors or flaps. And the trouble is the clients in question don't ever fully complete the DHCP transaction upon power up to assign an ip - so they can't connect -but if I assign an IP manually on the client - then they can connect right up to Citrix servers.
>
> That's why I figured get a packet capture to look at.
>
> Thanks,
>
> -Jeff
>
>
> -----Original Message-----
> From: Heath Jones [mailto:hj1980 at gmail.com]
> Sent: Tuesday, September 21, 2010 10:52 AM
> To: Jeff Wojciechowski
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Embeded Packet Capture for DHCP Troubleshooting
>
> Is the switch in the middle doing anything 'funky', or just pretty bog standard?
> Are the clients configured to accept any dhcp response, or are they locked down in any way?
>
> If the ethernet port is flapping according to the client, it may make new requests when the link comes back up each time..
> If a client sees a gratuitous arp or packet from another host with the same IP address, it may drop the lease and request a new one..
>
> It sounds like it works though, they get the IP, but just keep asking when they don't need to (before dhcp lease expiry) ??
>
>
>
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