How to capture network traffic

Hi,

Can someone give me the clue on how to capture network traffic at gateway.

Thanx

get ethereal: http://www.ethereal.com/download.html

then choose the approperiate tool of interest

yes ethereal is a good way to start, but plz be aware, depending on who's traffic u decide to sniff. some org have tools to detect this type of activity, and there exists network architecure issues such as PPP or switches/firewalls that may need additional tools for penetration. i discourage any activity other than for self learning purposes.