All IPv4 addresses:

cat access.log |awk '/^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/ {print $1}'

All IPv6 addresses:

cat access.log |awk '!/^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/ {print $1}'

Unique first block prefixes:

cat access.log |awk '!/^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/ {print $1}'| awk -F: '{print $1}'|sort -n| uniq -c|sort -nr

Unique full prefixes (but might be full address):

cat access.log |awk '!/^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/ {print $1}'| awk -F:: '{print $1}'|sort|uniq -c|sort -nr