From: Peter Valian (valianp@southwestern.edu)
Date: Wed Mar 21 2001 - 23:15:40 CST
Nick,
We have the exact topology you describe. Each of our residence halls
has its own subnet.
When a client wants a DHCP leases it broadcasts it to the subnet. Your
router will have a virtual interface for each subnet and that interface
will have an ip address on that subnet (we use xxx.xxx.xxx.1 as our
virtual interface IP addresses for each subnet). The router will hear
the broadcast on that IP and pass the DHCP request along to your helper
address (which is your NetReg box).
The helper address and the BOOTP protocol (DHCP is an extension of
BOOTP) takes care of your DHCP routing concerns. The DHCP server knows
which subnet to reply to. If you need a better explanation, it's
probably in the BOOTP RFC (951) and the Directed ARP RFC (1433).
I can probably provide you with examples from our network if you need.
hope this helps.
-peter
Nick Ciesinski wrote:
>
> Currently our university is on a flat network (no routing enabled). This
> summer we are upgrading our backbone and will be moving to a routed
> environment (255.255.255.0). I noticed the mention of the ip helper-address
> for Cisco equipment in the readme for netreg, but had a few questions to
> make sure I understand what needs to be done because I don't want to be
> running around like a chicken with its head cut off during the summer when
> this all takes place.
>
> We currently have 14 residence halls and to make it easy every one of our
> halls has one subnet. From what I am understanding I will need to enable
> the ip helper-address to point to the DHCP/Registration server for each of
> the subnets, correct? Now here is where my question comes into play.. How
> is the DHCP server going to know what subnet the IP address needs to be in
> that it will give the machine requesting the IP? Also, how is the DHCP
> server going to reply to the computer issuing the request because the reply
> is a broadcast?
>
> I want to believe that the helper takes care of everything but I don't want
> to make that assumption and when summer comes along it doesn't work. I am
> sure someone out there runs in a routed environment so if someone could
> answer my questions that would be great.
>
> Thanks
>
> Nick Ciesinski
> UW-Whitewater, Residence Life
>
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-- Peter Valian Network & Systems Administrator Southwestern University Georgetown, Texas 512.863.1586 office 512.863.1605 fax -- ********************************************************************** To unsubscribe from this list, send an e-mail message to majordomo@southwestern.edu containing a single line with the words: unsubscribe netreg Send requests for assistance to: owner-netreg@southwestern.edu **********************************************************************
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