two nics, same network, different topics

[Bill Paul]

[...]

> We're using Netramet and Nemac to get data from the flows. If the mirror 
> iface has an ip address, Nemac cannot "poll" (or whatever it's called it 
> does) data from Netramet and the bge0 card and saying something like no 
> response from x.x.x.3 (it's the fxp0 card). (It's kinda strange, and 
> kinda offtopic, but networking related.) If I say, ifconfig bge0 delete, 
> it works again.
> 
> The metering card has an IP address because tcpdump would complain (no 
> IPv4 address) and maybe it affects it's capabilities. (I'm not so sure.)

Uh... no. Whether or not the interface has an IP address does not
"affect its capabilities." If all you want to do is snoop traffic
via tcpdump (or something like it), you don't need an IP address
on the interface. Period. Snooping traffic is done via BPF, which
grabs all frames they even get anywhere near the IP layer. If you're
not actually using the bge0 interface to exchange any traffic, just
do ifconifg bge0 up and don't bother putting an IP address on it.
You'll still be able to put the interface into promiscuous mode and
monitor packets to your heart's content. Don't let the big bad
tcpdump warning message scare you.

-Bill

--
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-Bill Paul            (510) 749-2329 | Senior Engineer, Master of Unix-Fu
                 wpaul at windriver.com | Wind River Systems
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              <adamw> you're just BEGGING to face the moose
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