Re: Log DHCP request with Sniffer/Ethreal...

From: Roger Hunen (rhunen_at_xs4all.nl)
Date: 09/01/04 

Date: Wed, 1 Sep 2004 06:57:33 +0200

"Malic" <spam@houston.rr.spam> wrote...
> We are experiencing the following issue with new PCs we have purchased from
> IBM. We did not experience the issue with machines before the IBM
> thinkcentres we purchased.

You may be looking in the wrong place. This may not be IBM thinkcentre related
at all. You may be experiencing this problem simply because you have faster
machines now. Read on...

[snip]

> Issue:
> On a warm or cold boot, immediately login and it will not run our kixtart
> login script form Domain. After being logged in for 30 seconds to 1 minute
> we then get our network connection. Browse internet connec tto email etc...
> We have to log off and log back in to reprocess our login script.

This sounds _very_ familiar to me...

Assuming that you have a switched network, make sure that workstation ports
go into the forwarding state as soon as link integrity is established. On Cisco
switches the feature you are looking for is called 'portfast'.

Normal spanning tree behavior is to set a port blocking until the spanning tree
protocol has decided that it must be forwarding. This takes 30-40 seconds.
During this time the port blocks all traffic. So DHCP will fail and you cannot
talk to your domain controllers.

For old slow systems, this may not be a problem because the system boot
takes longer than it takes spanning tree to set the switch port forwarding.
New fast machines will complete the boot cycle before the port goes into the
forwarding state and have no network connection for some time.

When configuring portfast, the port goes into the forwarding state immediately
and the spanning tree protocol may switch is back to blocking if there is a good
reason to (no workstation attached but another network switch that is closer to
the spanning tree root).

Alternatively you can swith off spanning tree at workstation ports, but portfast
is much more fool proof.

Good luck,
-Roger 

--
E-mail: rhunen@xs4all.nl
Home: http://www.xs4all.nl/~rhunen

Relevant Pages

  • Re: Log DHCP request with Sniffer/Ethreal...
    ... go into the forwarding state as soon as link integrity is established. ... Normal spanning tree behavior is to set a port blocking until the spanning tree ... During this time the port blocks all traffic. ... takes longer than it takes spanning tree to set the switch port forwarding. ...
    (microsoft.public.win2000.networking)
  • Re: Log DHCP request with Sniffer/Ethreal...
    ... WSe have spanning tree turned off. ... > go into the forwarding state as soon as link integrity is established. ... > During this time the port blocks all traffic. ... > and the spanning tree protocol may switch is back to blocking if there is ...
    (microsoft.public.windows.server.active_directory)
  • Re: Log DHCP request with Sniffer/Ethreal...
    ... WSe have spanning tree turned off. ... > go into the forwarding state as soon as link integrity is established. ... > During this time the port blocks all traffic. ... > and the spanning tree protocol may switch is back to blocking if there is ...
    (microsoft.public.win2000.networking)
  • Re: Log DHCP request with Sniffer/Ethreal...
    ... > is bad and doesns't detect network speed until late in the login. ... I have seen a problem in the past where workstation and switch had problems ... >> Normal spanning tree behavior is to set a port blocking until the spanning ... >> During this time the port blocks all traffic. ...
    (microsoft.public.windows.server.active_directory)
  • Re: Log DHCP request with Sniffer/Ethreal...
    ... Were you able to get Ethereal working to sniff the port traffic? ... >> go into the forwarding state as soon as link integrity is established. ... >> Normal spanning tree behavior is to set a port blocking until the ... >> and the spanning tree protocol may switch is back to blocking if there ...
    (microsoft.public.win2000.networking)