Serving addresses to multiple subnets

[Paine, Thomas Asa]

     The man pages :)  

     It's crazy what one can find in those things, hehe.  That said, you are running some old (2.x) release, so I don't what those man pages might look like.  I'm glad to hear it's working for you though.

     man dhcpd.conf

"...
Some installations have physical networks on which more than one IP subnet operates.   For example, if there is a site-wide requirement that 8-bit subnet masks be used,  but a department with a single physical Ethernet network expands to the point where it has more than 254 nodes, it may be necessary to run two 8-bit subnets on the same Ethernet until such time as a new physical network can be added.   In this case, the subnet declarations for these two networks must be enclosed in a shared-network declaration.
..."

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
   Thomas Paine (paineta at uwec.edu)
   University of Wisconsin - Eau Claire
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 


-----Original Message-----
From: dhcp-users-bounces at lists.isc.org [mailto:dhcp-users-bounces at lists.isc.org] On Behalf Of John Tabasz (jtabasz)
Sent: Thursday, October 08, 2009 1:48 PM
To: Users of ISC DHCP
Subject: RE: Serving addresses to multiple subnets

It bloody worked!

Can I ask where you were able to dig up this information? Teach a man to fish and all. ;-)

Thanks a bunch,

John

-----Original Message-----
From: dhcp-users-bounces at lists.isc.org [mailto:dhcp-users-bounces at lists.isc.org] On Behalf Of Paine, Thomas Asa
Sent: Wednesday, October 07, 2009 2:46 PM
To: Users of ISC DHCP
Subject: RE: Serving addresses to multiple subnets

John,
	The Cisco router will not generate two relay requests, only one, and only for the primary address.  That said, however, you CAN use a shared network statement to wrap those two subnet statements together.  I think it will serve out the highest addresses first, but nonetheless I think it will do what you need.

Like this...

shared-network Foobar{
   subnet 10.1.100.0 netmask 255.255.252.0 {
   option routers 10.1.100.1;
     option subnet-mask 255.255.252.0;
     option domain-name-servers x.x.x.x;
     option domain-name "mydomain.com";
   deny unknown-clients;
   } 


   subnet 10.1.200.0 netmask 255.255.254.0 {
   option routers 10.1.200.1;
     option subnet-mask 255.255.254.0;
     option domain-name-servers x.x.x.x;
     option domain-name "mydomain.com";
   deny unknown-clients;
   }
}

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
   Thomas Paine (paineta at uwec.edu)
   University of Wisconsin - Eau Claire
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

From: dhcp-users-bounces at lists.isc.org [mailto:dhcp-users-bounces at lists.isc.org] On Behalf Of John Tabasz (jtabasz)
Sent: Wednesday, October 07, 2009 3:49 PM
To: Users of ISC DHCP
Subject: Serving addresses to multiple subnets

Hi,

I have a Cisco router with a secondary interface on one of the physical interfaces, e.g. 

Int fa0
   Ip address 10.1.100.0 netmask 255.255.255.0
   Ip address 10.1.200.0 netmask 255.255.255.0 secondary

My dhcp server is sending addresses to the primary subnet, but not to the secondary subnet.
There are subnet declarations for both subnets:

subnet 10.1.100.0 netmask 255.255.252.0 {
option routers 10.1.100.1;
  option subnet-mask 255.255.252.0;
  option domain-name-servers x.x.x.x;
  option domain-name "mydomain.com";
deny unknown-clients;
} 


subnet 10.1.200.0 netmask 255.255.254.0 {
option routers 10.1.200.1;
  option subnet-mask 255.255.254.0;
  option domain-name-servers x.x.x.x;
  option domain-name "mydomain.com";
deny unknown-clients;
}

And fixed address declarations for each of the hosts I want to serve addresses to. 
I can see the requests hitting the interface on my dhcp server via snoop, but no response is forthcoming. 

Any ideas?

Thanks,

John

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