Routing and DHCP

I've installed a new Aruba 2400 wireless mobility switch (which is
fantastic), however I'm having a little problem with DHCP. The Aruba switch,
and my Cisco switches are having problems routing DHCP requests. I did a
google search and found out about IP Helper, and enabled it on the Cisco
switch (it doesn't appear in the Aruba software), but that didn't help. I
read a little more, and IP Helper is designed for multiple VLANs, but we have
a flat network.

So... I read the event viewer (semaphore timeout period expired), so I ran
etheral, and I found that 4 DHCP Discover packets were sent
(.97,4.97,11.97,26.97 seconds), then 2 DHCP Inform packets (35.88,38.88
seconds), then a further DHCP Discover (64.10) followed by Offer, Request,
Ack (all at 64.10+a tiny bit)

However all non DHCP traffic seems fine. I even ran a terminal services
session to the DHCP server.

Any ideas or solutions greatly appreciated!

William Mann
IT Techinican, Trinity Catholic High School

> Any ideas or solutions great
ly appreciated!
>
> William Mann
> IT Techinican, Trinity Catholic High School
You tell nothing about DHCP relay agents... Are you sure that you
properly configured them on your routers?



--
With best regards
Nickolay Domukhovsky, MCSA

"Nick Domukhovsky" wrote:

>
> > Any ideas or solutions great
> ly appreciated!
> >
> > William Mann
> > IT Techinican, Trinity Catholic High School
> You tell nothing about DHCP relay agents... Are you sure that you
> properly configured them on your routers?
>
>
>
> --
> With best regards
> Nickolay Domukhovsky, MCSA
>

I'm pretty sure they're correctly configured - the routers, or switches are
Cisco Catalyst 2950SX running IOS 12.1. I used the IP Helper-Address command,
but like I said, we have a flat network with a single subnet -
10.201.252.0/22. I'm going to try other broadcast traffic

William Mann

Forget the relay agents,...get rid of them. You said you had a flat
network,...therefore the is no* LAN routing,...therefore there is no* reason for
the relays to exist.

DHCP on a flat network is extremely simple,...it either works,..or it doesn't.
If it doesn't,...then it is the DHCP Server's fault or there is a problem in the
Physical Layer (topology). DHCP does not depend on anything else when used on a
flat network.

Host-based Firewalls (like the Windows Firewall) "might" get in the way.
Windows Firewall should be disabled when troubleshooting.

There is really nothing more to say without knowing (in great detail) how your
LAN is designed at Layers 1, 2, and 3.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed (as annoying as they are, and as stupid as they sound), are
my own and not those of my employer, or Microsoft, or anyone else associated
with me, including my cats.
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"Trinity Catholic High School"
<(E-Mail Removed) om> wrote in message
news:412CD4E0-D3F6-4E3D-ABC5-(E-Mail Removed)...
>
>
> "Nick Domukhovsky" wrote:
>
>>
>> > Any ideas or solutions great
>> ly appreciated!
>> >
>> > William Mann
>> > IT Techinican, Trinity Catholic High School
>> You tell nothing about DHCP relay agents... Are you sure that you
>> properly configured them on your routers?
>>
>>
>>
>> --
>> With best regards
>> Nickolay Domukhovsky, MCSA
>>
>
> I'm pretty sure they're correctly configured - the routers, or switches are
> Cisco Catalyst 2950SX running IOS 12.1. I used the IP Helper-Address command,
> but like I said, we have a flat network with a single subnet -
> 10.201.252.0/22. I'm going to try other broadcast traffic
>
> William Mann

Well, I kind of figured out the problem. It appears that the STP on the cisco
and aruba switches was interfering with DHCP, when I switched off STP, DHCP
started working fine. Which is all very good, execpt now, I have no STP.
Thanks for the input Phillip - I thought it was the case that I didn't need
them, but I put them on just to be sure

Will.

"Phillip Windell" wrote:

> Forget the relay agents,...get rid of them. You said you had a flat
> network,...therefore the is no* LAN routing,...therefore there is no* reason for
> the relays to exist.
>
> DHCP on a flat network is extremely simple,...it either works,..or it doesn't.
> If it doesn't,...then it is the DHCP Server's fault or there is a problem in the
> Physical Layer (topology). DHCP does not depend on anything else when used on a
> flat network.
>
> Host-based Firewalls (like the Windows Firewall) "might" get in the way.
> Windows Firewall should be disabled when troubleshooting.
>
> There is really nothing more to say without knowing (in great detail) how your
> LAN is designed at Layers 1, 2, and 3.
>
> --
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
> The views expressed (as annoying as they are, and as stupid as they sound), are
> my own and not those of my employer, or Microsoft, or anyone else associated
> with me, including my cats.
> -----------------------------------------------------
> -----------------------------------------------------
>
>
>
> "Trinity Catholic High School"
> <(E-Mail Removed) om> wrote in message
> news:412CD4E0-D3F6-4E3D-ABC5-(E-Mail Removed)...
> >
> >
> > "Nick Domukhovsky" wrote:
> >
> >>
> >> > Any ideas or solutions great
> >> ly appreciated!
> >> >
> >> > William Mann
> >> > IT Techinican, Trinity Catholic High School
> >> You tell nothing about DHCP relay agents... Are you sure that you
> >> properly configured them on your routers?
> >>
> >>
> >>
> >> --
> >> With best regards
> >> Nickolay Domukhovsky, MCSA
> >>
> >
> > I'm pretty sure they're correctly configured - the routers, or switches are
> > Cisco Catalyst 2950SX running IOS 12.1. I used the IP Helper-Address command,
> > but like I said, we have a flat network with a single subnet -
> > 10.201.252.0/22. I'm going to try other broadcast traffic
> >
> > William Mann
>
>
>

"Trinity Catholic High School"
<(E-Mail Removed) om> wrote in message
news:7AE57A95-B07E-425F-A1ED-(E-Mail Removed)...
> Well, I kind of figured out the problem. It appears that the STP on the cisco
> and aruba switches was interfering with DHCP, when I switched off STP, DHCP
> started working fine. Which is all very good, execpt now, I have no STP.
> Thanks for the input Phillip - I thought it was the case that I didn't need
> them, but I put them on just to be sure

I have never ever had to disable STP. There is no reason is should have any
relationship to DHCP. But, unfortuneately I have no suggestions.

Hmm...you sure you don't have any physical "loops" with the switches in the
physical way the cables are plugged in? The purpose of (one of) STP is to
handle redundant pathes at Layer2. It finds two or more pathes to the same
place and disables all but one and holds the others as "backups". If you have
your cabling screwed up it could be that STP is shutting down a link that just
happens to be the only physical path the DHCP Server can use. I cannot picture
in my mind how I could cause that on purpose,...but you need to examine that
possibility.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed (as annoying as they are, and as stupid as they sound), are
my own and not those of my employer, or Microsoft, or anyone else associated
with me, including my cats.
-----------------------------------------------------