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

[olethros.livejournal.com]

Hmm, this could go a couple of ways depending on what Zen have in mind - and I don't have enough info about that to be able to say for sure.

I'll point you in both directions and see what falls out. There are two ways of routing your /29.

One is that your ADSL line and your LAN are two separate networks, with two different address allocations. The ADSL line will have (say) a /30 - two reserved, one their end, one the ADSL card on your PC router. Separately, Zen's router will have a configuration set that any traffic for 82.68.129.72/29 will be fired at your router, and it's up to it to do the right thing from there.

The other way is as I think you suspect - every device on your network lies inside that /29, including your main PC. This is how my DSL back at home works, but in your instance it's slightly wackier because your ADSL card and your LAN need to be on the same logical network and have addresses on the same subnet. If that is how you're supposed to set this up then you'll need to enable bridging in some manner between your ADSL card and your LAN interface.

wechsler had the idea that you could split your /29 into two /30s, and assign one to the ADSL link and the other to your LAN - but while that's possible it (like either of the above) will only work if that's how Zen expect you to do it.

Sorry if that's clear as mud -- bother me at Whitby for more info. :)

[ruis.livejournal.com]

If you split it into /30s you waste 2 IPs, leaving you with only 2 for hosts.

[wechsler.livejournal.com]

The neglected detail was that I said that was pointless...