Which edition are you playing?
The truth is, it varies by which sub-edition you're using.
In all of them, the TN is changed. Either the defense adds to the range, or replaces the range, and you compare the original attack roll against the adjusted TN.
Non-defense melee is usually TN5, but it can vary by weapon. Lightsabers have a higher TN of 15, for example, and axes are 10. This is used as if "range" for all the discussion purposes.
In all cases, dodge is only vs ranged weapons, parry only versus melee weapons.
1E: Core only
Dodge/parry adds to all opponent's TN's to be hit that segment against that kind of weapon.
Shield reaction TN by range. Success adds shield's rating to hull code for damage for one attacker.
No Haste action; Everyone's first action comes in segment 1; second actions in segment 2, etc.
1.1E: 1E Core plus Rules Upgrade flyer
Full dodge/full-parry/full-evasion introduced. Adds roll to TNs to be hit for whole round.
Reaction dodges/parries/evasions replace TN to be hit from range, but only for one attacker.
Shield reaction TN by attacker's roll. Success adds shield's rating to hull code for damage for one attacker.
Haste Actions merely move you to front of the queue.
1.5E: 1E Core plus Rules Companion
Full dodge/full-parry/full-evasion included. Adds roll to TNs to be hit for whole round. Only allowed to be combined with a single move action.
Reaction dodges/parries/evasions replace TN to be hit from range, but only for one attacker.
Shield reaction TN by attacker's roll. Success adds shield's rating to hull code for damage for one attacker.
Haste Actions move to front of queue, but full-round and reaction defenses have to be hasted to be able to affect hasted attacks.
2.0E: Core Rules (Blue cover)
Full dodge/full-parry/full-evasion included. Adds roll to TNs to be hit for whole round. Only allowed to be combined with a single move action.
Reaction dodges/parries/evasions replace TN to be hit from range for rest of round. Use better of roll or range based TN.
Shields are full round action, TN by number of facings applied to. Success adds shield's rating to hull code for damage for one attacker.
No haste action.
2.5E: 2E Revised and Expanded (Color Cover)
No full round defenses. No haste.
Reaction defenses replace TN to be hit, even if lower!
Shields are full round action, TN by number of facings applied to. Success adds shield's rating to hull code for damage for one attacker.
d6 Space
Melee to hit: 10
ranged to Hit 5 to 20 (10+ modifier on page 73)
Full Defense: TN 10+Defense Roll, no other actions.
Partial Defense: replaces range based TN on all attacks.
No reaction defenses.
Shield difficulty by number of faces covered. (p.70)
Note: D6 space also has different damage systems