Not all DHCP options are going through DHCP relay

Discussion in 'Server Networking' started by JN, Jul 7, 2009.

  1. JN

    JN Guest

    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, Jul 7, 2009
    #1
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  2. 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

    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.
     
    Ace Fekay [Microsoft Certified Trainer], Jul 8, 2009
    #2
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  3. JN

    JN Guest

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


    "Ace Fekay [Microsoft Certified Trainer]" <>
    wrote in message

    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

    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, Jul 8, 2009
    #3
  4. And does the documentation or tech support indicates it supports it?

    Ace
     
    Ace Fekay [Microsoft Certified Trainer], Jul 8, 2009
    #4
  5. 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/s..._Switches_Advanced_Configuration_Examples.pdf

    My suggestion is to call 3Com support.

    Ace
     
    Ace Fekay [Microsoft Certified Trainer], Jul 8, 2009
    #5
  6. JN

    JN Guest

    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.


    "Ace Fekay [Microsoft Certified Trainer]" <>
    wrote in message
    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/s..._Switches_Advanced_Configuration_Examples.pdf

    My suggestion is to call 3Com support.

    Ace
     
    JN, Jul 8, 2009
    #6
  7. 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
     
    Ace Fekay [Microsoft Certified Trainer], Jul 8, 2009
    #7
  8. 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?


    --
    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.
    -----------------------------------------------------
     
    Phillip Windell, Jul 8, 2009
    #8
  9. 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]" <>
    wrote in message 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.
     
    Phillip Windell, Jul 8, 2009
    #9
  10. JN

    JN Guest

    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?
     
    JN, Jul 8, 2009
    #10
  11. 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
     
    Ace Fekay [Microsoft Certified Trainer], Jul 8, 2009
    #11
  12. JN

    JN Guest

    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.


    "Ace Fekay [Microsoft Certified Trainer]" <>
    wrote in message
    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
     
    JN, Jul 9, 2009
    #12
  13. I guess they've got bitten by the economic bug, too!

    Oh well...
     
    Ace Fekay [Microsoft Certified Trainer], Jul 9, 2009
    #13
  14. 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.

    --
    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.
    -----------------------------------------------------
     
    Phillip Windell, Jul 9, 2009
    #14
  15. Sounds like my older daughter! :)

    Ace
     
    Ace Fekay [Microsoft Certified Trainer], Jul 9, 2009
    #15
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