Which Google Bot UA is correct?

I'm seeing two variations on the 2.1 bot

[GaryK]

Googlebot/2.1 (+http://www.google.com/bot.html)
Googlebot/2.1 (+http://www.googlebot.com/bot.html)

Both resolve to google.com. Are they both valid? I sure miss being able to search WW via Google as I'm sure there's already an answer to this question. I'm also going to contact Google about this but thought I might get a faster answer here. Thanks in advance.

~gary.

[volatilegx]

I believe they are both used by Google.

[incrediBILL]

It doesn't matter which is correct, authorize them by IP only to stop fakers.

Google has the following IP ranges:

64.233.160.0 - 64.233.191.255
66.249.64.0 - 66.249.95.255
72.14.192.0 - 72.14.239.255
216.239.32.0 - 216.239.63.255

[GaryK]

Thanks Dan. Bill, I do that plus other stuff for my own servers, but I also maintain and distribute a browscap.ini file and want it to be accurate. I appreciate your help as it gave me the answer I was looking for. Thanks. :)