Geek help: static IP addresses

[ciphergoth]

Quick geek help sought with making sure I understand IP routing properly.

Zen have allocated me the static IP address block 82.68.129.72/29. Of these eight addresses, one is the network address, one is the broadcast address.

I've fitted an ADSL card to my main PC, saltationism. So it has two interfaces: an ADSL interface and a LAN one. That's two more addresses taken. So there are four left: I can give up to four more machines on the LAN static IP addresses.

The thing that worries me is that if the subnet for the LAN is 82.68.129.72/29, then can I assign an address from that subnet to the ADSL card? If I do, will my LAN be able to route to that address? If not, what should I do instead?

Comments

[kimble.livejournal.com]

Is the ADSL (ppp) interface automatically negotiating its IP with the remote end, and if so, is it being allocated an address in that subnet?

I'm with Nildram, not Zen, but I have a single (static) IP as part of the basic service in addition to my routed subnet. On the router (a linux box with USB stingray thing, so I'd guess functionally equivalent to your PCI setup) I have a ppp0, which has the single static IP (which isn't part of my subnet) and an eth0 that I've allocated the first IP from my subnet to.

I've heard that it's possible to get a ppp device to use the same IP as eth0, but haven't tried that myself. I have (accidentally, cos I didn't read the instructions properly) previously set the router up to give ppp0 an address from my subnet, and that didn't seem to break anything - but was a waste of a perfectly good IP address.

YMMV

[kimble.livejournal.com]

To clarify: when I said "didn't seem to break anything", I had the router doing 1:1 NAT at the time, with a private address range on the LAN, thereby avoiding the routing headache described above...