Ignoring certain hosts

[storm <storm-shadow () comcast net>]

Keep getting hit with broadcasts from my ISP.  So I would like to not see these in the alerts anymore.
And, sometimes when a user accesses our file server (legit user), snort reports: [1:2102:1] NETBIOS SMB 
SMB_COM_TRANSACTION Max Data Count of 0 DOS Attempt [**].   Would like to ignore all internal traffic and broadcasts 
from ISP. 

In the faqs, it said to write pass rules and add the hosts to the portscan-ignorehosts list . Then to call snort with 
the -o option to activate the pass rules. Can anyone elaborate on this? 

TIA
storm