One DHCP Server, Multiple routed subnets, roaming clients

James Jalbert jjalbert at rsu39.org
Tue Oct 27 17:47:05 UTC 2009


I am sure that this has been asked, and answered, but I can not find the solution anywhere. I have a DHCP server in my main building. This building also connects to 6 other building through a WAN. I have one DHCP Server (Ubuntu server9.04, DHCP 3.1) with multiple subnet decelerations, and one large host file, added with an include. Everything works great. I have machines that roam between buildings, and as long as I use comma separated fixed address, everything works great.
Now I would like to be able to set up the server so that, if a machine has a deceleration with a fixed address, but is requesting an ip form another building, it would be assigned a dynamic address, however if there is no Host deceleration(an unknown client) it will not be assigned any address. 

Here is a sample of my config so far:

ddns-domainname "foo";
ddns-rev-domainname "in-addr.arpa";
ddns-update-style interim;
ddns-updates on;
max-lease-time 86400;
default-lease-time 86400;
option domain-name-servers 10.11.0.4, 130.111.xx.xx, 130.111.xx.xx;
option domain-name "foo";
deny unknown-clients;
deny client-updates;
allow duplicates;
authoritative;
update-static-leases on;

## All hosts go here
include "/etc/dhcp3/ip.hosts";


# Main-Building
subnet 10.11.0.0 netmask 255.255.248.0 {
	option routers 10.11.0.1;
	range 10.11.5.1 10.11.7.254;
	}
# Building1
subnet 10.11.8.0 netmask 255.255.252.0 {
	option routers 10.11.8.1;
	range 10.11.11.2 10.11.11.254;
	}
#Building2
subnet 10.11.12.0 netmask 255.255.254.0 {
	option routers 10.11.12.1;
	}
# Building3
subnet 10.11.14.0 netmask 255.255.254.0 {
	option routers 10.11.14.1;
	}
# Building4
subnet 10.11.16.0 netmask 255.255.255.0 {
	allow unknown-clients;
	option routers 10.11.16.1;
	range 10.11.16.100 10.11.16.243;
	}
# Building5
subnet 10.11.17.0 netmask 255.255.255.0 {
	option routers 10.11.17.1;
	}
# Building6
subnet 10.11.18.0 netmask 255.255.254.0 {
	option routers 10.11.18.1;
	}
In the main building, I can add allow unknown-clients, and any one who walks in can get an address, such as seen in building4, without unknown-clients only address are handed out to host in the host file. The big hurdle is I only want our company's machines to be registered, I do not want anyone walking in off the street to be assigned an address, but if an employee goes from the main building to building 3, they would get an address in that subnet.

Here are a few host decelerations:

# RoamingSystem1
host RoamingSystem1 {
	hardware ethernet 00:25:4B:9B:28:F1;
	fixed-address 10.11.0.170,10.11.8.104,10.11.14.175,10.11.19.7,10.11.12.181;
	ddns-hostname "RoamingSystem1";
	option host-name "RoamingSystem1";
}

# RoamingSystem1-Wireless
host RoamingSystem1-Wireless {
	hardware ethernet 00:25:4B:D1:70:94;
	fixed-address 10.11.0.170,10.11.8.104,10.11.14.175,10.11.19.7,10.11.12.181;
	ddns-hostname "RoamingSystem1-Wireless";
	option host-name "RoamingSystem1-Wireless";
}

# System1-might-roam
host System1 {
	hardware ethernet 00:1F:F3:D8:BA:EF;
	fixed-address 10.11.3.110;
	ddns-hostname "system1";
	option host-name "system1";
}


James Jalbert
Network Administrator
Caribou School Department
Phone: 207-493-4246
E-Mail: jjalbert at caribouschools.org






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