tcpdump/bpf and seeing .1q tags

Charlie Schluting charlie at schluting.com
Wed Mar 9 12:32:44 PST 2005


Charlie Schluting wrote:
> Charles Swiger wrote:
> 
>> On Mar 9, 2005, at 2:22 PM, Charlie Schluting wrote:
>>
>>> More importantly, I'm trying to figure out if a bpf read will see 
>>> them as well. Any insight on this?
>>
>>
>>
>> Yes, or it will if you use promisc mode and an appropriate BPF filter:
>>
> 
> So promisc is enabled in my case.
> 
> This seems to imply that the bpf will always see the vlan tags. (I don't 
> want to.. that was the point of my question)
> 
> I believe this is starting to make sense. Thanks for your reply.

Oh! Er.. I hit send too fast.

So a BPF is supposed to ignore vlan tags unless 'vlan' is specified??

-Charlie


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