[lug] IP on computer, not modem

[Carl Wagner]

David L. Anselmi wrote:
> Alfred G. de Wijn wrote:
>   
>> I've recently moved a lot of services to a VPS, so I no longer need a static IP at home.
>>     
> [...]
>   
>> The only thing is that I would very much like to keep the globally routable IP on the
>> computer.
>>     
>
> Apologies to Nate but I had a hard time following.  You have two things going on: bridge mode and 
> static IP.
>
> If you turn off bridge mode (switch to routed mode) then your DSL modem will have two IPs: the 
> external one will be the globally routable one, the internal one will be unrouteable, and the modem 
> will do NAT between them (which doesn't stop you from forwarding traffic in to your computer if you 
> want it to offer services to the world).
>
> You could have done this in the first place and used port forwarding to your server, unless you were 
> using a block of public IPs.  Staying in bridged mode gains you little now, I think, but it's your 
> 'net.  I don't know whether QWest charges differently for bridged mode, I haven't heard that they do.
>   
I have Qwest with the cheap ActionTec modem. I had it in routing mode 
when I got it
but later changed to bridging mode so my WRT54G w/dd-wrt would be my 
firewall.
(finer control over the firewall)
> I think QWest has to agree to bridged mode for you to use it so changing that would require a 
> conversation with them.  But I'm not sure.
>   
It's all done in the modem/router - Qwest doesn't know or care.
> If you give up your static IP (mine is only $5/mo so it isn't the expensive part of the setup), 
> you'll still get a public (routable) one but it won't stay the same.  That can be worked around with 
> dyndns if necessary.  But in order to assign your IP, QWest will use DHCP.
>
> If you use routed mode, the modem will work out the IP assignment with QWest and you won't care.  In 
> bridged mode, your computer has to work out the IP assignment--I assume that's DHCP.
>
> How is your computer assigned an IP now?  Presumably you set it manually to what QWest gave you. 
> Theoretically, you can call Qwest and tell them to cancel your static IP.  Then run DHCP on your 
> computer and it will talk to the QWest DHCP server to get its IP dynamically.
>
> Will QWest insist that you drop bridging when you switch to DHCP?  I don't know.  Do they have to do 
> anything to change from bridged to routed?  I don't know.
>   
No. As above, they don't know or care. The way I view it, by switching 
to bridging
mode, you give the router a lobotomy and it then just converts the 
packets from DSL
to Ethernet, without actually looking at the contents. In bridging mode 
it doesn't do
DHCP, Routing, Firewall, etc., just media conversion.

Carl

> HTH,
> Dave
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