Yes you are correct, that is the correct IPv6 address; we can use the two ways of shortening to simplify the address; suppression and compression. In cisco it is called IPv6 address shortening; removal of the leading zeros in the suppression, and in compression is replacing the longest consecutive zero segments with a double colon and of cause this is done once in an address.
2001:db8::ff00:42:29 – Is the correct answer
Common mistakes are:
a. Omitting zeros twice in an address and replacing with double colon ::
b. Removal of trailing zeros
Example:
IPv6 address
2001:0db0:0000:0000:0ab0:0000:0000:0adc
Correctly simplified address:
2001:db0::0ab0:0:0:adc or 2001:db0:0:0:ab0::adc
Incorrect:
a. Omitting zeros twice within one address:
2001:db0::0ab0::0adc
b. Removal of trailing zeros:
2001:db::ab:0:0:adc