Re: Not all DHCP options are going through DHCP relay
- From: "JN" <me@xxxxxxxx>
- Date: Wed, 8 Jul 2009 11:43:00 -0400
The switch is the 3Com 4500. The PoE model with 50 ports which is model
3CR17572-91.
"Ace Fekay [Microsoft Certified Trainer]" <aceman@xxxxxxxxxxxxxxxxxxxxxxx>
wrote in message news:%23sOw9w1$JHA.5092@xxxxxxxxxxxxxxxxxxxxxxx
"JN" <me@xxxxxxxx> wrote in message
news:OM$Vk50$JHA.1380@xxxxxxxxxxxxxxxxxxxxxxx
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/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.
--
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
aceman@xxxxxxxxxxxxxxxxxxxxxxx
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.
.
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