I haven't been around here since about the time SR4 came out. I was dusting off my copy, and having committed myself to learning the new system, I have a quick and probably silly question.
Full Defense. What if you do not have the Dodge skill? Can you default to Dodge in that situation? I need an example please.
Thanks!

Full Defense

Reaction + Dodge + Dodge
or
Reaction + melee combat skill + Dodge

I am assuming you are asking about a situation where the PC does not have Dodge Skill so the question is;

Reaction + Dodge(Reaction -1) + Dodge(Reaction -1) allowed?

Since Dodge is a defaultable skill, actually, I think you can.

That was what I came up with, but...
If you have a decent Agility, Dodge becomes unessecary. (Agilty 5 in a gunfight gets you Reaction + (Agility-1)? Why buy Dodge unless you are going to exceed 4? I think I am missing something important.

Full dodge against firearms is reaction + dodge. If you don't have dodge, it's just reaction.

(Gymnastics works as well).

It's a bit more complex than that:

Ranged:
Reaction + dodge
Reaction + gymnastics

Close combat:
Reaction + dodge + close combat skill
Reaction + close combat skill x2

I'd assume that if you have no dodge, gymnastics, or close combat skills you actively defend with only your reaction (note that aborting to a reactive defense refreshes your dodging pool (iirc) so there might still be a reason to go on active defense even if you don't have a defensive skill.

So for some reason, you cannot Default to a pretty basic skill (Dodge-Moving out of the Way) when you would actually need to? That seems counter-intuitive to the defaulting rules.

For some strange reason (that I don't know) you use your reaction if you don't have dodge instead of reaction-1 like normal defaulting.

Seems to be the way for ranged combat .

Whoops, had it backwards for full defense in close combat; it's reaction + dodge x2 or reaction + close combat skill + dodge