I am not sure if "bridging" is the answer here. If you think differently and has another suggestion, you are welcome!

The problem:
We have a firewall with two interfaces: wan/lan. The wan interface is connected to a router, the router to a modem and the modem to a coaxial cable provided by our ISP.
Near to our office a truck crashed badly against a pole on the street and destroyed that coaxial cable. As result we lost our internet connection and the ISP told us the repair could take almost a week.

An alternative:
We have good 3G/HDSPA cellular connection here. To connect to internet we use a USB modem and it connects using PPP as usual. It works in my laptop with fedora 10; NetworkManager auto config it, no problems.

The question:
How to share this connection on my Fedora 10 in a way our firewall could see the laptop as a router ?
(the firewall does not recognizes the USB modem and even so, it does not have PPP)

I have tried with the command "brctl addif br0 eth0" and "brctl addif br0 ppp0" but looks like any host on the same laptop's lan interface could not reach hosts on the wan interface (ppp0), like the default router for that connection for instance.

anyone has some experience with this kind of network ?

any hints or ideas are welcome,

Well this wouldn't ever be a bridge, I think you should just need to enable ip_forward and ip masquerading then when traffic is routed to that laptop it'll go out to the net as if it were from the laptop itself.

http://tldp.org/HOWTO/html_single/Ma...-Simple-HOWTO/

Wouldn't it be easier to just plug the laptop into the wan port of the existing router, and then just setup the laptop up just like sharing with just one other computer (the router in this case)?

I wish !
The WAN port of the router is a serial one with a big connector. I don't remember its name but it is typical on these kind of equipment.

It will depend massively on what your real router actually is, but generally you shouldn't have a problem routing back into your network for the laptop. Maybe you can add a separate vlan or at least just a separate subnet on the inside to stop asymmetric routing if that becomes a problem for you.

I checked the router´s manual. It is a V.35 connector.

T H A N K Y O U V E R Y M U C H !

From the document you suggested it worked on the first attempt, using the setup on section 2, for dial up connections. Very simple. very straight !

Currently, I am writing this from my desktop using the original setup for web proxy, default gateway, etc.

I never thought it could be so easy...

Next monday, the users will never find there was a problem at all !

cheers !

Super. From what you said about your setup there's probably something *theoretically* bad about what's going on, but that's not exactly the point... I was expecting much more of a mess to ensue from this!

I guess it is more simple than that. I replaced the router and the Cisco modem by the laptop and pluged the laptop where the router used to be, on the WAN interface of the firewall.
I put on the laptop's iface the same IP the router had, so the firewall didn't notice nothing.

The real test will be on Thursday when the people return from the carnival (for sure, not all Brazilians likes the carnival - I am here working and having fun ) and start to send e-mails with big attachments and surfing on the net.

let's see...

cheers,