The doc page on the ports that Couchbase Server uses doesn't list the "dedicated / admin" ports. These ports are used by the cluster manager (ns_server) when communicating with memcached. The default values for these ports are:
- Dedicated Port: 11209
- Dedicated TLS Port: 11206
The dedicated port is used by ns_server so that it can always get to memcached to issue important control commands (like creating buckets, creating vbuckets, issuing compaction commands etc) and won't get starved for access by too many front end connections.