[lug] Network bridge

[Jason Vallery]

On Sun, Nov 30, 2008 at 7:06 PM, Aaron Nichols <anichols at trumped.org> wrote:
> On Sun, Nov 30, 2008 at 4:58 AM, Jason Vallery <jason at vallery.net> wrote:
>> Hi All,
>>
>> I'm beating my head against the wall on this one so I thought I'd send
>> an email in case someone can see the obvious error in my ways.  I've
>> got a Fedora 10 box that I'd like to setup networking monitoring on.
>> I'd like to ensure that I capture all traffic the crosses my existing
>> router/gateway.
>>
>> My thought is that I could set it up like this:
>>
>> Internet->router/gateway->eth0 (fedora box) eth1 -> switch -> LAN.
>
> You would probably have a lot less trouble if you used the Linux box
> as the router and dumped the bridge approach. Does the router do
> something special which necessitates this setup? Instead of one point
> of failure (and troubleshooting) you've now got two.

Mainly because I figured it would be a lot more work.  I already have
the Fedora box doing other things so I didn't want to setup a
completely separate box.  I already have a hardware router/gateway.
Do you know of a good how-to that would make setting it up in this
fashion easy for me?  I could just use a pre-built distro like
clarkconnect or smoothwall but that we require more hardware.


>> On the Fedora box I have setup a bridge (br0) and enabled promiscuous
>> mode on eth0 and eth1 (I can't seem to set br0 to promisc).  I've
>> configured sysctl to ignore birdged traffic and not process ipchains
>> rules.  I still can't get anything from eth1 to talk to the
>> router/gateway.  The Fedora box can get to the internet just fine.
>
> Does anything connected to eth1 successfully get ARP responses for the
> router or the fedora box itself? If you look at hosts on the LAN, what
> do their arp tables show?
>

I've reverted my network config back at the moment so I'm unable to do
any further testing at this point.  Hopefully I'll have some time to
revisit this later in the week.

-J





-- 
Jason Vallery
jason at vallery.net

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