Creating Subnet, Some Questions.

[zeroburn]

Hello to all. I am running my network and am wanting to create a subnet, if thats what i am actually looking for.

I would like to have my server rack to have a firewall and seen by the rest of the network as one ip, i guess is my goal.

I want to do this so that my experimentation and projects would not disrupt the rest of the network, and so i can set up DHCP, a firewall, ext inside the network.

If anyone knows how to do this, let me know. Thanks.

[Rob Pomeroy]

You could use a NATing firewall/router, or you could configure one of your servers as a router - ideally it would need at least two network cards for that.  Then use separate physical network switches for each network, or use the VLAN capabilities of a managed switch.

[zeroburn]

I have some Entresys Matrix E7 chassis with managed switches, but i am in need of reading the manual through first (over 1000 pages). On the servers using the new sub-network, what configurations would need to be changed? (Ubuntu Server 12.04)

Thanks for helping out.

[DaveLembke]

I agree with Robs suggestion to have 2 NICs and physically isolate the networks as the best and easiest method.

I have never run 2 DHCP's on the same network, but I suppose one way to have 2 DHCP networks running on the same network and not compete would be to assign reservations for devices by MAC address to designate which DHCP's would handle each NIC. Lots of work, and if you have DHCP (A) and DHCP (B) and a reservation for 01:55:EF:04:77:3A on DHCP (B), I would think that you would have to black list it from DHCP (A) so that DHCP (A) does not give it a dynamic IP from its subnet. This is hypothetically speaking since I have never attempted to run 2 DHCP's on the same LAN. There is the chance that both DHCPs would battle it out competing to be heard. As well as what happens when you introduce a new Networked device to the network that has no reservation on either, would both DHCP servers try to give it an IP or would it be the DHCP server with the fastest response to the request for the stack. And the worst scenario a network storm crippling the network! 

[Rob Pomeroy]

what configurations would need to be changed? (Ubuntu Server 12.04)

Gateway?  Network?  Subnet mask?  Routing tables?  Hard to say without a bit more flesh on the bones.

[Rob Pomeroy]

I have never run 2 DHCP's on the same network

Don't do it.  Physically or logically isolate (separate switches/VLANs).  Managing two DHCP servers on the same LAN would be a full time job.