From: Nick Ciesinski (fletch26@charter.net)
Date: Thu Mar 22 2001 - 01:34:37 CST
Thanks for the info.. I will take a look at them RFC's to get a clear
understanding of how it works behind the scenes.
Another question I have is in regards to the ip forward-protocol command
with Cisco equipment. We currently are using Cabletron (Enterasys)
equipment but we will be switching to Cisco in the summer so I am new to
some of Cisco's features. Would it be advisable to use the ip
forward-protocol command to limit what traffic is forwarded to the netreg
server? I notice that by default the helper will send all udp and nd
traffic to the machine you give as the helper, I know that I wouldn't need
nd sent because we don't have any old SUN systems, but at the same time is
it worth the effort? Also from looking at the help on this it seems like I
can specify what udp ports to send and break it down to DHCP/BootP only, is
this correct as well?
Nick
-----Original Message-----
From: owner-netreg@southwestern.edu
[mailto:owner-netreg@southwestern.edu]On Behalf Of Peter Valian
Sent: Wednesday, March 21, 2001 11:16 PM
To: netreg@southwestern.edu
Subject: Re: DHCP in a routed environment
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 ******************************************************************************************************************************************** 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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