In short, I'm looking for a way to obtain multiple IP addresses via DHCP on a single NIC. For a more elaborate explanation, see below.
I'm working on a router / firewall in a somewhat arcane network setup. The situation is as follows: I live in a student dorm with a farily large local 100 Mbit network, where everyone has a single network outlet. For every system you want to use on the network, you have to register it's MAC adress before you can use it. When a computer is used, it gets its IP address via DHCP, but only if it's MAC is registered. Otherwise, you'll get a very short term address that you can only use to register your MAC via a special web page. If a system isn't used for a long time, it is automatically unregistered. On the local network, you can have multiple systems active at the same time. However, internet access is provided via a single PPPoE connection per person. What I am trying to do, is using an OpenBSD computer as firewall and gateway for my computers. It sits between the large local network, and my personal switch. Internet access is shared via NAT, but on the local dorm network I want each of my PC's to have it's own IP address using Binat. The problem is that I need to obtain multiple IP addresses via DHCP on the single external NIC of the router (which is connected to the dorm LAN). Also, the DHCP leases should be renewed using the registered MAC addresses as identifiers. Using static aliasses is prohibited and as such not an option. Is there a way to do this? Just sending additional MAC addresses via dhclient.conf doesn't work. It would be ideal to have some sort of virtual NIC's that have the external NIC as parent physical device, but none of the OpenBSD pseudo devices appear to be really suitable for this purpose. Using a virtual device would have the extra advantage of being able to use the ($if) notation in PF, so that it can react to changes in IP addresses. Otherwise, I will have to find a way for PF to discover the addresses on boot time. Any thoughts? Regards, Richard Noorlandt
