Is this possible? (re. multiple external IP's)

Sumanji · 4 Nov 2009 at 15:50

Hey,

We've got a 3Com 3CRWDR300A-73 router running on ADSL24's service here. They've supplied us with 8 static IP's, of which only 5 are usable by devices.

What I want is to keep all 5 x Windows PC's under one external IP, and therefore fully firewalled. And then I want a few other devices (2 x PS3, IP Phone) to have their own external IP's and to be put in the DMZ.

Is this possible?

Cheers,

Su

wij · 4 Nov 2009 at 16:09

It looks like it might but from the quick read of the instruction booklet it's not totally clear.

I think you'd need to create a 2nd VLAN on the router and set it up with no-nat and give it a static route but again I'm not entirely sure that is correct. No real experience of 3Com kit at all - I know what you want to do is perfectly easy to set up on things like DrayTek's 2820 series though as they support a 2nd routed subnet for just this purpose.

If you're directly routing devices you shouldn't need to be messing around with putting them into a DMZ as they are effectively going to be publicly visable and reachable anyway - that would be the whole point of a non-nat set up.

Sumanji · 4 Nov 2009 at 16:42

Hey,

Ok cool that's a helpful nudge in the right direction I guess

I'm a bit out of my depth here to be honest... here are some router screens of the VLAN stuff... not sure what to put in those boxes tbh!

Cheers,

Su

tolien · 4 Nov 2009 at 18:22

It's possible (I do it with my 877) but whether your router will do it is another story - it seems to be a feature that damned few routers do (or indeed, do right; probably because virtually no one uses it).
I use multiple NAT rules: 1:1 NAT for the hosts you want to give a public IP to and the standard NAT overload for the rest of the machines. Internally, all the machines get an IP in whatever range you want (I use 192.168.1.0/24) then you either use NAT loopback or an internal DNS server to use the RFC1918 IPs rather than the public ones on the inside.

That VLAN stuff all looks internal and so pretty useless.

Sin_Chase · 4 Nov 2009 at 20:49

Those 3-coms usually have 1-to-1 NAT in the DMZ section.

Sumanji · 4 Nov 2009 at 22:59

Sin_Chase,

I did spot that, but didn't think it would be that simple... can I just put the external IP I want to use in the left column, and the internal IP on the right?! That would be too good/simple to be true

Cheers,

Su

Sumanji · 5 Nov 2009 at 19:08

Hey,

Well I tried just setting it up simply by typing public IP in the left column and local IP in the right... seems to have worked!!

Both PS3's show "NAT Type 2" when simultaneously connected, which never used to happen before.

So thanks all

Su