[lug] router in bridge mode

D. Stimits stimits at attbi.com
Tue Aug 20 10:12:23 MDT 2002

Kenneth D. Weinert wrote:
> Hash: SHA1
> Forwarding a question that's a bit beyond my ken - any thoughts are 
> appreciated:
>  techie question - if an ISP says they're going to set your SDSL router up in 
> "bridge" mode with 1 or 2 IP addresses, what does that mean? Is it still a 
> router that can share the connection with as many computers as you hub in?
> Personally I still don't have a home network set up because I'm trying to get 
> it sorted - too much hands-on hardware :)
> Thanks in advance for any assistance.

I don't know about the dedicated devices, but I've been running on a 
Linux bridge for the last couple of weeks now (still tweaking). YMMV.

The bridge is like a piece of wire, nothing knows it is there. If you 
used it for communicating between two local machines, they would use the 
IP address assigned by the ISP. So MachineA going to MachineB would 
traverse the internal network, through the bridge, to the ISP, back to 
the bridge, through the internal net again, and to the other machine. 
However, if you have linux machines involved, you can assign multiple IP 
addresses to each NIC (I've asked a lot of questions lately related to 
this). If you have a switch/hub connecting local machines to the bridge, 
and each machine has both its DHCP and internal non-Internet address, 
then they can talk directly (I think network neighborhood does not 
require an IP, so perhaps this works with windows as well). If you do 
have windows machines involved, you can tell the linux bridge to deny 
all traffic in/out on port 137 through 139, so only machines inside of 
the bridge can use network neighborhood (so far I have not set up 
network neighborhood for the local windows machines, there has not been 
a need yet).

D. Stimits, stimits AT attbi.com

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