When attempting to counterspell a spell, it says you add your counterspell dice to the resistance roll. So when they say counterspell dice, is it only those given by the skill, or does that include its linked attribute too? The example in the SR4A book unhelpfully only mentions how many "hits" they got and not what was rolled.

Your Counterspelling pool is the base resist stat (usually Willpower) and Counterspelling. Counterspelling can be either your own skill, or the skill of the mage covering you; I'm not sure if there is stacking when you get two mages together. Anyway, that is all you get to roll; Stat+Counterspelling.

I'm not sure where you would use the linked attribute.

I thought so. Yeah, that's the part that gets me. You could have a magic rating of 20, but unless you put some points into counterspelling, you would be helpless to defend against incomming spells. Seems a bit odd.

If it helps, think of it as being a weapons developer who never stopped to think about how to defend against them. Come to think of it, wasn't that the plot of Iron Man? Damien Knight Tony Stark nearly gets killed by his own mortar shell, and realizes that he should put some points into Armor Design?

On the upside, you can always bind a Counterspelling Focus - that should let you get above the skill limits. I suppose you could also specialize in Counterspelling (Combat Spells) to get a few extra points.

You add the Counterspelling rating to the resisting stat for spells cast at a protected target. To dispel a sustained or quickened spell, you use Counterspelling + Magic.

Well, a mage could keep a bound spirit in the astral running counterspelling on them and do the teamwork test thing. That's a pretty good defense I suppose, though the teamwork test will likely not add more than a couple dice to the test. If you use an oversummoned spirit, it could take over as the primary dice pool source and provide you with substantial defenses.

There's another counterspelling thread somewhere that discussed counterspelling wrt the astral/physical plane divide. I think it was the general consensus that to use counterspelling on someone you must share the same plane (where dual-natured beings are considered present on both). Even if I'm mistaken about the consensus, I would still take this position on the grounds that spells themselves cannot cross the divide.