Re: DHCP relay, superscope and laptops
- From: "Pall Bjornsson" <palli@xxxxxxx>
- Date: Wed, 4 May 2005 17:43:20 -0000
> Superscopes are only needed when the DHCP server offers
> addresses to a MULTINET.
In my case I have a L3 Switch that splits my network in a few distinct VLANs
each of which has it's own subnet. The Switch then acts as a DHCP relay,
relaying DHCP requests to a central DHCP server, which then must offer IP
addresses for different subnets.
I was under the impression that if you had such a setup, you MUST have
superscope(s) set up, right ?
What we did as a workaround, was that we created one superscope for each
VLAN/Subnet and that seems to do the trick, but maybe that's not the way to
go ?
Regards,
Palli
"Herb Martin" <news@xxxxxxxxxxxxxx> wrote in message
news:%23TEc8b0SFHA.204@xxxxxxxxxxxxxxxxxxxxxxx
> "Pall Bjornsson" <palli@xxxxxxx> wrote in message
> news:ORLfJorSFHA.3184@xxxxxxxxxxxxxxxxxxxxxxx
>> Hi !
>>
>> I have a DHCP server serving a few seperate subnets. One subnet, which is
>> out of the superscope,
>
> What's the superscope for?
>
> Superscopes are only needed when the DHCP server offers
> addresses to a MULTINET.
>
> Multinet = more than one logical IP subnet on the same cable
> segment, or more accurately, the "same broadcast domain."
>
>> ...is the one that the DHCP server is in, all the other
>> subnets are within the superscope. The other subnets connect through a
>> Level 3 Switch/Router which acts as a DHCP relay agent.
>
> Subnets on differnt cables should be in different scopes and
> should NOT have a superscope.
>
> Superscopes are groups of scopes on the same segment,
> which is very unusual (not unheard of, but not very common.)
>
>> For most of the time everything works fine, until I have to take my
>> laptop
>> and connect it to different subnets. My laptop has a fixed IP address,
>> assigned through DHCP as an indefininite reservation of IP address, on
>> the
>> "primary" subnet, as there are some firewall filters to handle traffic to
> it
>> from both the internet, and the other subnets (for management purposes).
>>
>> When I connect my laptop to any of the other subnets, which are in the
>> superscope, I get an IP address.
>>
>> When I then connect it to the next subnet in the superscope, I don't get
> an
>> address via DHCP until I delete the assignment from the first subnet.
>>
>> What I most would like to do is to manually reserve indefinitely one IP
>> address for my laptop in each subnet, which would be allocated via DHCP
> when
>> I connect to that subnet. That way I could set up some filter exceptions
>> that would only work for that IP address.
>>
>> Thus, there are two questions:
>>
>> 1. How can I get this fixed IP address in each subnet to be allocated to
> my
>> laptop ?
>
> Start with deleting the superscope.
>
> Before leaving a location you may (optionally) type:
>
> ipconfic /release
>
> Then when you move to a new location you can just type:
>
> ipconfig /renew
>
> (The renew will work without the release, but release is
> a good idea if you pool of addresses on the first net is
> relatively small -- universities have hundreds of people
> leaving one subnet for another after every class, or when
> leaving the dorms in the morning, etc.)
>
>> 2. How can I get an IP address allocated each time I connect to a subnet
>> without having to manually delete the first reservation?
>
> Modern machines (Win2000+) will usually figure it out if
> you REBOOT, but the problem is more irritating with sleep
> (hibernate or suspend).
>
> You may have to perform the "ipconfig /renew".
>
>
.
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