Reading raw ethernet

[Paul Khavkine]

On Fri, 19 Aug 2005, Julian Elischer wrote:

>Paul Khavkine wrote:
>> Hi guys.
>>
>>
>> I'm writing a small program to read raw ethernet frames out of netgraph
>> to capture Spannign Tree packets from the switch.
>>
>> Is it possible to pick up STP frames without putting the interface in
>> promiscuous mode ?
>
>If you don't put it in promiscuous mode, then you will only see broadcast
>packets and packets aimed at you specifically.
>
>If that's enough then there is nothing in netgraph that insists that
>you turn on promiscuous mode.

Well STP packets are sent to a well known MAC address (multicast?)
so i can't see it if the card is not in promisc mode.
I'm not exactly sure if it's good or not to leave it in promisc mode
all the time, is there any security/performance issues with that on a
busy server?
I want to read STP packets to monitor the link with the switch, if i can't
hear the switch for X amount oof time, failover to another NIC.
Is it possible to have more then one MAC on a NIC ? I have bge and em
cards.

>
>You should probably look at the ng_etf node too BTW.

How does ng_etf deal with that ?


Thanx
Paul

>
>
>>
>> Thanx
>> Paul
>>
>> ************************************************
>> Paul Khavkine
>> Networks/Systems Planning and Engineering
>> DISTRIBUTEL Communications.
>> 740 Notre Dame West, Suite 1135
>> Montreal, Quebec, Canada, H3C 3X6
>> +1-514-877-5505 x 263
>> http://www.distributel.net
>> ************************************************
>>
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>
>

************************************************
Paul Khavkine
Networks/Systems Planning and Engineering
DISTRIBUTEL Communications.
740 Notre Dame West, Suite 1135
Montreal, Quebec, Canada, H3C 3X6
+1-514-877-5505 x 263
http://www.distributel.net
************************************************