Error for Firesheep: "Couldn't get netmask for device en1: en1: no IPv4 address assigned"

I wanted to try out the Firesheep addon for Firefox but I get the following error:

Couldn't get netmask for device en1: en1: no IP开发者_高级运维v4 address assigned

I'm using MacBook Pro (Snow Leopard). Any ideas?

Are you sure it should be en1 and not some other interface? Run ifconfig (type ifconfig in the console) and check, it may be different (e.g., en0), and then change the value in Firefox (type about:config and change the value for capture interface, I'm not sure about the exact name of the field).

Hope it helps.