fixed address in dhcp server

digsecurity · 07-08-2010, 03:43 AM

Hi all,
I want to set up a dhcp server such that the clients get same ip every time. Giving fixed address to every client would be a long process.

"I don't want to assign a specific ip to the client but what i want is the server provides same ip every time"

Is there a way. Thanks in advance

deadeyes · 07-08-2010, 04:36 AM

You can make the lease very long.

But I would not rely on it if you want to firewall specific IPs.

On all platforms you will have to add entries "manually".
Actually, if you create a list of mac addresses and of IPs, you can very easily script adding all the IPs.

barghota · 07-08-2010, 05:48 AM

You would want to assign IP per MAC address,

This is a sample...

Quote:

subnet 192.168.0.0 netmask 255.255.255.0 {
option routers 192.168.0.3;
option subnet-mask 255.255.255.0;

range 192.168.0.20 192.168.0.90;
default-lease-time 216000;
max-lease-time 432000;

host HostA {
hardware ethernet 00:16:6f:62:49:b4;
fixed-address 192.168.0.20;
}
host HostB {
hardware ethernet 00:1f:3c:8c:4a:e0;
fixed-address 192.168.0.21;
}
}

digsecurity · 07-08-2010, 06:21 AM

I was wondering if there's a way server provides same ip without assigning ip per MAC address. I have clients more than 70 and binding all MAC would be a headache....Is there a way server does this automatically?

Thanks

barghota · 07-08-2010, 08:00 AM

You could set that a lease never expires in the leases file:

lease 192.168.0.88 {
starts 3 2010/03/24 19:26:19;
ends never;
tstp 3 2010/03/24 21:22:09;
binding state active;
hardware ethernet 00:0c:29:45:15:3c;
}

Note that the leases file is build with the MAC address, you won't have to declare it per IP.

If you have a populated leases database, you could set all the leases to "ends never;" using sed...

# mv dhcpd.leases old.dhcpd.leases && sed 's/ends .*;/ends never;/g' old.dhcpd.leases > dhcpd.leases

digsecurity · 07-08-2010, 11:26 PM

Thanks, I'll give it a try

deadeyes · 07-09-2010, 01:33 AM

As I said, you can script it.
You will have the same issue having to put the stanza with the mac there 70 times.