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?

Show quote Hide quote 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/ipaddr/configuration/guide/iad_dhcp_rly_agt.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.

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


Show quoteHide quoteThat'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/ipaddr/configuration/guide/iad_dhcp_rly_agt.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.

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

Ace

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/switches/7750/10015464_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/switches/3Com_Stackable_Switches_Advanced_Configuration_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/Hardware/Networking_Hardware/Switches/Q_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/Hardware/Networking_Hardware/Switches/Q_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/Hardware/Networking_Hardware/Q_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 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/switches/7750/10015464_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/switches/3Com_Stackable_Switches_Advanced_Configuration_Examples.pdf

My suggestion is to call 3Com support.

Ace

Show quote Hide quote 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

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 $$$.


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?
Show quoteHide quote

Well, whenever I go there without a Google referral, it points me to create an account.

Start your "free" trial here!
https://secure.experts-exchange.com/register.jsp?cid=1325
Then it goes on saying...
$12.95/month
$59.95/6 months
etc...

So how do you go about creating an account to respond to posts without paying?

Ace

Maybe it is because I had the account for a few years and they might have
just started charging.  I just tried to join on another computer and I was
also prompted to pay as well.  WOW.


Well, whenever I go there without a Google referral, it points me to create
an account.

Start your "free" trial here!
https://secure.experts-exchange.com/register.jsp?cid=1325
Then it goes on saying...
$12.95/month
$59.95/6 months
etc...

So how do you go about creating an account to respond to posts without
paying?

Ace

I guess they've got bitten by the economic bug, too!

Oh well...

My account has been there since 2000 (or so...I think,...can't remember).  I
forgot it was even there.  I just started posting replys in their forums
there maybe two months ago.  I'm up to 4th in the rank on their "points
reward system" in the ISA/TMG forum.  That is the only "pay" I know of.

I post answers (at least some call them that anyway  :-) ) on
www.experts-exchange.com,... www.isaserver.org,... and here in the groups to
keep myself busy during the day and to help try to keep my mind "on the
subject" and fresh.  I'm not sure if that part is working, but it does keep
me busy when it's quiet and there are no things to "fix" here at work.   I
know I don't get a dime for any of it,...I just get some "free" grief from
posters from time to time  when I don't tell them what they want to hear.

Show quote Hide quote Sounds like my older daughter! :-)

Ace

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.

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

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