Bridging and giving the bridge an IP address

Bridging and giving the bridge an IP address

Post by Scott He » Tue, 28 Oct 1997 04:00:00



I'm attempting to use the kernel bridging code to set up a network
on the following skeleton:

 +-----+  100mbit  +-----------+ 10mbit +----+
 | *.2 |====x======| LINUX *.4 |========|    |
 +-----+ crossover +-----------+        | 10 |
                                        |mbit|
                         +-----+        |hub |
                         | *.1 |========|    |
                         +-----+        +----+

LINUX is kernel 2.0.30 running with two NICs, with the *.4 IP address
at eth0 on the hub side of things.  The goal is 100mbit between *.2
and LINUX, while allowing 10mbit communications between everyone else.

On LINUX, I can "ifconfig eth1 up", and run "brcfg -enable", and
things mostly work.  Unfortunately, "ping *.255" from the *.2 box
gives responses from all boxes on the hub excepting *.4.

Using tcpdump, I find that eth1 is seeing packets like "arp who-has
*.4 (Broadcast) tell *.2", and the same packets are seen on eth0.
This indicates to me that LINUX is bridging the broadcast packets,
before the networking code gets a chance to reponse to them.

Any ideas on this?  I suspect that there's someplace in the bridging
code where it's not accounting for local interfaces, only those on
the connected networks.  [I realize that bridges aren't "supposed"
to have IP addresses at all, but I'll just live with 10mbit rather
than have one box dedicated to bridging.]  "ifconfig eth1 *.6"
allowed *.2 to ping *.6, but not *.4.

Unfortunately, there are some internal reasons why *.2 has to see
LINUX as *.4, and not *.6.  I need broadcast across the bridge, so
I can't solve this by making LINUX a router.

One solution that's come to mind would be to change *.2 and *.6 to
put them in a different subnet, and have LINUX route the subnets
for "normal" packets and bridge the subnets for broadcast packets.
This seems a bit extreme, though.

Thanks,
--

<Favorite unused computer book title: The Compleat Demystified Idiots
  Guide to the Zen of Dummies in a Nutshell in Seven Days, Unleashed>

 
 
 

Bridging and giving the bridge an IP address

Post by jaya » Wed, 29 Oct 1997 04:00:00




Quote:> I'm attempting to use the kernel bridging code to set up a network
> on the following skeleton:

> On LINUX, I can "ifconfig eth1 up", and run "brcfg -enable", and
> things mostly work.  Unfortunately, "ping *.255" from the *.2 box
> gives responses from all boxes on the hub excepting *.4.

Scott, I don't think I can help with your query, but hopefully you can help
me! I am also attempting to use bridging, but for me it doesn't work at
all. I have recompiled my kernel with bridging enabled (CONFIG_BRIDGE=y in
.config, according to the HOW-TO) but when I do "brcfg -enable" I get the
error msg that the doco says means you don't have bridging compiled into
the kernel. I know I'm properly compiling as I can turn other things on and
off. I've also tried several different kernels from 2.0.25 to 2.0.31 (but
not the 2.0.30 you're using). I have 3 NICs, all of which are working just
fine (I see traffic on all when I run TRAFSHOW).

It sounds like we're trying to achieve similar results, so if I can get
bridging at least enabled then I may be able to shed some light on your
problem.

Regards,
James Gallagher

--
"They say hard work never hurt anybody, but I figure why take the chance."
                                                            -- Ronald
Reagan

 
 
 

Bridging and giving the bridge an IP address

Post by Scott He » Tue, 11 Nov 1997 04:00:00




   I'm attempting to use the kernel bridging code to set up a network
   on the following skeleton:

    +-----+  100mbit  +-----------+ 10mbit +----+
    | *.2 |====x======| LINUX *.4 |========|    |
    +-----+ crossover +-----------+        | 10 |
                                           |mbit|
                            +-----+        |hub |
                            | *.1 |========|    |
                            +-----+        +----+

   LINUX is kernel 2.0.30 running with two NICs, with the *.4 IP
   address at eth0 on the hub side of things.  The goal is 100mbit
   between *.2 and LINUX, while allowing 10mbit communications between
   everyone else.

   On LINUX, I can "ifconfig eth1 up", and run "brcfg -enable", and
   things mostly work.  Unfortunately, "ping *.255" from the *.2 box
   gives responses from all boxes on the hub excepting *.4.

The solution, such as it was, was to give the *.4 box another IP
address for the 100mbit network, set an explicit route on *.4 to find
*.2 on that interface, and use /sbin/arp to explicitely ask the second
interface on *.4 to respond to the *.4 address - even though it isn't
actually that address.

There are still some bugs lurking in this solution, and I'm not
terribly happy with it.  It works, but it gives me the willies
regarding whether it will always work, especially WRT which machines
come up first in case of a set of reboots...

--

<Favorite unused computer book title: The Compleat Demystified Idiots
  Guide to the Zen of Dummies in a Nutshell in Seven Days, Unleashed>

 
 
 

1. bridging problem -- bridge needs IP address

Hi everyone,

i tried to set up a bridge with my fedora core 3, kernel
2.6.10-1.741_FC3. I entered following commands:

# ifconfig eth0 promisc up
# ifconfig eth1 promisc up
# brctl addbr br0
# brctl addif br0 eth0
# brctl addif br0 eth1
# ifconfig br0 up

It was possible to create the bridge, but there is a problem: The
bridge doesn't forward traffic until i assign an IP address to the
interface br0. But that's not what i want.
Any ideas?

Greetings

Peter

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