You shouldn't do it that way....

Either use thresholds (look at threshold.conf), where you can supress a signature either by source or destination IP, make sure you select the last option (in the examples of threshold.conf) to totally supress the signature. This is the easiest way.

The other way is to use a pass rule. Basically, you create a rule the same as you would a normal rule, but make sure it matches whatever you are trying to filter out, so for example:

pass <ip_to_ignore> any -> any 1434 (msg:"Ignore 1434 from X"; sid:15000000

You MUST be EXTREMELY careful with pass rules. A poorly written one can cause real stuff to be missed, make sure it matches exactly with the circumstance.

In your case, I'd recommend the threshold...