yup .. this was it .. Thanks :) There's a problem in gentoo's ippool.conf
# ## If you prefer to allocate a random IP address every time, i
# ## use this query instead
allocate-find = "SELECT framedipaddress FROM ${ippool_table} \
WHERE pool_name = '%{control:Pool-Name}' \
AND expiry_time IS NULL \ ( failed to alocate before because expiry_time = NULL isn't valid .. had to replace with IS NULL ) ..
ORDER BY RAND() \
LIMIT 1 \
FOR UPDATE"