Not all DHCP options are going through DHCP relay

On my Win 2000 DHCP server I have option 252 set (wpad option for
autodetecting proxy server). This works fine on my network whose ip range
is 192.168.100.x. We are expanding so we:

Installed a 3Com Layer 4 switch Model 4500
Added VLAN 2
Configured VLAN 1 ip on switch to 192.168.100.253
Configured VLAN 2 ip on switch to 192.168.101.253
Added static routes to switch to route between VLANs
Added scope to DHCP server for 192.168.101.x network.

All works perfectly for VLAN 2 network to get the right IP addresses from
the DHCP server and routing through VLANs is working as well. The only
problem is computers on the new 192.168.101.x network do not seem to be
getting the dhcp option 252 passed to them. None of the clients are
autodetecting the proxy server as they do when the same computers are on the
100.x network.

The computer can reach the proxy server fine if I manually configure IE so
it is not a routing or security issue. Is there something I need to
configure in the switches relay agent to pass option 252?

"JN" <(E-Mail Removed)> wrote in message news:OM$Vk50$(E-Mail Removed)...
> On my Win 2000 DHCP server I have option 252 set (wpad option for
> autodetecting proxy server). This works fine on my network whose ip range
> is 192.168.100.x. We are expanding so we:
>
> Installed a 3Com Layer 4 switch Model 4500
> Added VLAN 2
> Configured VLAN 1 ip on switch to 192.168.100.253
> Configured VLAN 2 ip on switch to 192.168.101.253
> Added static routes to switch to route between VLANs
> Added scope to DHCP server for 192.168.101.x network.
>
> All works perfectly for VLAN 2 network to get the right IP addresses from
> the DHCP server and routing through VLANs is working as well. The only
> problem is computers on the new 192.168.101.x network do not seem to be
> getting the dhcp option 252 passed to them. None of the clients are
> autodetecting the proxy server as they do when the same computers are on the
> 100.x network.
>
> The computer can reach the proxy server fine if I manually configure IE so
> it is not a routing or security issue. Is there something I need to
> configure in the switches relay agent to pass option 252?
>
>
>


That's a good question. My first thought is first, does the switch support the full range of available DHCP options based on the RFC, and if so, how would it be enabled, which is your question anyway. My first guess would be to contact the switch vendor if its documentation doesn't indicate it, or if there are no commands that reference the options when you configure the DCP Relay agent or IP helper (or whatever it is called on that specific name brand switch).

And of course this is all assuming that Microsoft's DHCP relay/agent topology supports all the options, which I believe it does since it supposedly follows RFC 3046 (http://tools.ietf.org/html/rfc3046). Now the question is, does the switch?

Out of curiosity, I checked Cisco concerning their switches, and the only reference I can find is for Option 082 (DDNS).
http://www.cisco.com/en/US/docs/ios/...html#wp1121812

Do you have the docs for the switch? Post the switch vendor and model for us. Maybe someone else is familiar with the model, or we can search for it. Worst case scenario is call the vendor.

--
Ace

This posting is provided "AS-IS" with no warranties or guarantees and confers no rights.

Please reply back to the newsgroup/forum to benefit from collaboration among responding engineers, as well as to help others benefit from your resolution.

Ace Fekay, MCT, MCSE 2003 & 2000, MCSA 2003 & 2000, MCSA Messaging
Microsoft Certified Trainer
(E-Mail Removed)
http://twitter.com/acefekay

For urgent issues, you may want to contact Microsoft PSS directly. Please check http://support.microsoft.com for regional support phone numbers.

The switch is the 3Com 4500. The PoE model with 50 ports which is model
3CR17572-91.


"Ace Fekay [Microsoft Certified Trainer]" <(E-Mail Removed)>
wrote in message news:%23sOw9w1$(E-Mail Removed)...
"JN" <(E-Mail Removed)> wrote in message
news:OM$Vk50$(E-Mail Removed)...
> On my Win 2000 DHCP server I have option 252 set (wpad option for
> autodetecting proxy server). This works fine on my network whose ip range
> is 192.168.100.x. We are expanding so we:
>
> Installed a 3Com Layer 4 switch Model 4500
> Added VLAN 2
> Configured VLAN 1 ip on switch to 192.168.100.253
> Configured VLAN 2 ip on switch to 192.168.101.253
> Added static routes to switch to route between VLANs
> Added scope to DHCP server for 192.168.101.x network.
>
> All works perfectly for VLAN 2 network to get the right IP addresses from
> the DHCP server and routing through VLANs is working as well. The only
> problem is computers on the new 192.168.101.x network do not seem to be
> getting the dhcp option 252 passed to them. None of the clients are
> autodetecting the proxy server as they do when the same computers are on
> the
> 100.x network.
>
> The computer can reach the proxy server fine if I manually configure IE so
> it is not a routing or security issue. Is there something I need to
> configure in the switches relay agent to pass option 252?
>
>
>


That's a good question. My first thought is first, does the switch support
the full range of available DHCP options based on the RFC, and if so, how
would it be enabled, which is your question anyway. My first guess would be
to contact the switch vendor if its documentation doesn't indicate it, or if
there are no commands that reference the options when you configure the DCP
Relay agent or IP helper (or whatever it is called on that specific name
brand switch).

And of course this is all assuming that Microsoft's DHCP relay/agent
topology supports all the options, which I believe it does since it
supposedly follows RFC 3046 (http://tools.ietf.org/html/rfc3046). Now the
question is, does the switch?

Out of curiosity, I checked Cisco concerning their switches, and the only
reference I can find is for Option 082 (DDNS).
http://www.cisco.com/en/US/docs/ios/...html#wp1121812

Do you have the docs for the switch? Post the switch vendor and model for
us. Maybe someone else is familiar with the model, or we can search for it.
Worst case scenario is call the vendor.

--
Ace

This posting is provided "AS-IS" with no warranties or guarantees and
confers no rights.

Please reply back to the newsgroup/forum to benefit from collaboration among
responding engineers, as well as to help others benefit from your
resolution.

Ace Fekay, MCT, MCSE 2003 & 2000, MCSA 2003 & 2000, MCSA Messaging
Microsoft Certified Trainer
(E-Mail Removed)
http://twitter.com/acefekay

For urgent issues, you may want to contact Microsoft PSS directly. Please
check http://support.microsoft.com for regional support phone numbers.

"JN" <(E-Mail Removed)> wrote in message news:OpSPDL%23$(E-Mail Removed)...
> The switch is the 3Com 4500. The PoE model with 50 ports which is model
> 3CR17572-91.

And does the documentation or tech support indicates it supports it?

Ace

"JN" <(E-Mail Removed)> wrote in message news:OpSPDL%23$(E-Mail Removed)...
> The switch is the 3Com 4500. The PoE model with 50 ports which is model
> 3CR17572-91.

I searched around a bit. I found one post in the experts-exchange.com forum, which stated the following concerning Option 252:
"Problem is 4500 because not layer 3 switch.
You need 4800 or 5500 switch for these features.
Vlan 1 and vlan 2 have interfaces configured on the 4500, but it has no routing capabilities between vlans.
Thats why you need more advanced layer 3 switch (eg. 4800 or 5500) and then with udp-helper your option 252 problem can be solved as well."

I also found the release notes for this switch at the following link. It doesn't mention anything about this feature.
http://support.3com.com/documents/sw...464_readme.pdf

I also found the Advanced Configuration guide in the following link. It doesn't mention anything about it.
http://support.3com.com/documents/sw...n_Examples.pdf

My suggestion is to call 3Com support.

Ace

What a co-incidence. That is my post asking the question there as well.
Unfortunately, that is the second time I have seen JanSc respond to a
question "It can't be done with that stuff" and been wrong which is why I
came here. If you look at a previous post of mine that JanSc responded to
you can see they said that the switch was not a layer 3 (it is) and that I
could not accomplish this:

http://www.experts-exchange.com/Hard..._24523938.html

However I posted back that this can be done and I had use Amerdog's config
setup from post:

http://www.experts-exchange.com/Hard..._23866460.html

Then in the post you found they says there is no UDP Helper (there is) and
again that it can't be done. My switch does also have UDP helper
capabilities shown in the Readme.pdf you posted so I will check to see if
this helps. Thanks for that and checking around!

http://www.experts-exchange.com/Hard..._24550757.html

I know JanSc means well, but this is not the first time I have been involved
in a thread where they have posted information that is not correct. I don't
want to be rude to them, but mis-information can propagate very easily
especially on these expert boards.


"Ace Fekay [Microsoft Certified Trainer]" <(E-Mail Removed)>
wrote in message news:u8wOnV%23$(E-Mail Removed)...
"JN" <(E-Mail Removed)> wrote in message
news:OpSPDL%23$(E-Mail Removed)...
> The switch is the 3Com 4500. The PoE model with 50 ports which is model
> 3CR17572-91.

I searched around a bit. I found one post in the experts-exchange.com forum,
which stated the following concerning Option 252:
"Problem is 4500 because not layer 3 switch.
You need 4800 or 5500 switch for these features.
Vlan 1 and vlan 2 have interfaces configured on the 4500, but it has no
routing capabilities between vlans.
Thats why you need more advanced layer 3 switch (eg. 4800 or 5500) and then
with udp-helper your option 252 problem can be solved as well."

I also found the release notes for this switch at the following link. It
doesn't mention anything about this feature.
http://support.3com.com/documents/sw...464_readme.pdf

I also found the Advanced Configuration guide in the following link. It
doesn't mention anything about it.
http://support.3com.com/documents/sw...n_Examples.pdf

My suggestion is to call 3Com support.

Ace

"JN" <(E-Mail Removed)> wrote in message news:(E-Mail Removed)...
> What a co-incidence. That is my post asking the question there as well.
> Unfortunately, that is the second time I have seen JanSc respond to a
> question "It can't be done with that stuff" and been wrong which is why I
> came here. If you look at a previous post of mine that JanSc responded to
> you can see they said that the switch was not a layer 3 (it is) and that I
> could not accomplish this:
>
> http://www.experts-exchange.com/Hard..._24523938.html
>
> However I posted back that this can be done and I had use Amerdog's config
> setup from post:
>
> http://www.experts-exchange.com/Hard..._23866460.html
>
> Then in the post you found they says there is no UDP Helper (there is) and
> again that it can't be done. My switch does also have UDP helper
> capabilities shown in the Readme.pdf you posted so I will check to see if
> this helps. Thanks for that and checking around!
>
> http://www.experts-exchange.com/Hard..._24550757.html
>
> I know JanSc means well, but this is not the first time I have been involved
> in a thread where they have posted information that is not correct. I don't
> want to be rude to them, but mis-information can propagate very easily
> especially on these expert boards.

I only take those boards with a grain of salt. I wasn't sure if that guy was right or not, but I knew it's a layer 3 switch, which supports IP (layer 3!!). When I search for things, and get that site, experts-exchange.com, I carefully weigh all the responses. I do find that many are erroneous, however I've found some good info there, too. So I try to weigh what's being posted based on my own knowledge, just using it as a guide to look elsewhere. I also find that charging for help, such as they do, and getting a 50-50 shot at whether the responses are right or wrong, even if they stamp the post 'Accepted Solution,' which it may not necessarily be the correct solution, is wrong, and frankly, not worth the subscription. Not that I am trying to knock them, but let's face it, we are all here to help and provide a much diverse and collaborative atmosphere here in the Microsoft free public newsgroups, with numerous talent and years of experience than there is in the finite list of posters at that site or any other pay-for-service site. And funny, many times they post Microsoft KB articles for solutions, anyway! So I can understand what you are saying. I guess it comes down to the individual that responds whether they are helpful or not.

Ok, back to business. As for the DCHP options on that switch, I have no idea! :-) I didn't find anything in the PDFs regarding this setting, or even if there is one, other than a mention for Option 082 (DDNS), so I am not sure. Maybe you'll find something I missed.

Ace

"JN" <(E-Mail Removed)> wrote in message
news:OM$Vk50$(E-Mail Removed)...
> Installed a 3Com Layer 4 switch Model 4500
> Added VLAN 2
> Configured VLAN 1 ip on switch to 192.168.100.253
> Configured VLAN 2 ip on switch to 192.168.101.253
> Added static routes to switch to route between VLANs
> Added scope to DHCP server for 192.168.101.x network.

Although it is not the source of this problem,....there is not supposed to
be a Static Route. You have a single Router sitting between two
subnets,....therefore the router is already fully aware of the location of
both networks. Static Routes are only used for destinations that are more
than one "router hop" from the source.

> The computer can reach the proxy server fine if I manually configure IE so
> it is not a routing or security issue. Is there something I need to
> configure in the switches relay agent to pass option 252?

What is the actual URL you are using on the DHCP Option?


--
Phillip Windell

The views expressed, are my own and not those of my employer, or Microsoft,
or anyone else associated with me, including my cats.
-----------------------------------------------------

They charge people $$$?

They don't pay the guys answering the questions anything (!'m one of them).
I guess the Site owners get all the $$$.


--
Phillip Windell

The views expressed, are my own and not those of my employer, or Microsoft,
or anyone else associated with me, including my cats.
-----------------------------------------------------


"Ace Fekay [Microsoft Certified Trainer]" <(E-Mail Removed)>
wrote in message news:(E-Mail Removed)...
"JN" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
elsewhere. I also find that charging for help, such as they do, and getting
a 50-50 shot at whether the responses are right or wrong, even if they stamp
the post 'Accepted Solution,' which it may not necessarily be the correct
solution, is wrong, and frankly, not worth the subscription.

I have an account which allows me to post and I don't pay either. Maybe
because I answer more questions that I ask? Don't know?
"Phillip Windell" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> They charge people $$$?
>
> They don't pay the guys answering the questions anything (!'m one of
> them). I guess the Site owners get all the $$$.
>
>
> --
> Phillip Windell
>
> The views expressed, are my own and not those of my employer, or
> Microsoft,
> or anyone else associated with me, including my cats.
> -----------------------------------------------------
>
>
> "Ace Fekay [Microsoft Certified Trainer]" <(E-Mail Removed)>
> wrote in message news:(E-Mail Removed)...
> "JN" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
> elsewhere. I also find that charging for help, such as they do, and
> getting a 50-50 shot at whether the responses are right or wrong, even if
> they stamp the post 'Accepted Solution,' which it may not necessarily be
> the correct solution, is wrong, and frankly, not worth the subscription.
>
>