In case the host parameter is provided as a FQDN (SLAVEOF host port), slave full resync is performed twice.

slave log:

[13868] 16 Oct 11:28:30.119 # Server started, Redis version 2.8.17
[13868] 16 Oct 11:28:43.881 * DB loaded from disk: 13.762 seconds
[13868] 16 Oct 11:28:43.882 * The server is now ready to accept connections on port 6400
[13868] 16 Oct 11:28:43.888 * Connecting to MASTER detta1-redis-db-901.data.det:6400
[13868] 16 Oct 11:28:43.889 * MASTER <-> SLAVE sync started
[13868] 16 Oct 11:28:43.889 * Non blocking connect for SYNC fired the event.
[13868] 16 Oct 11:28:43.889 * Master replied to PING, replication can continue...
[13868] 16 Oct 11:28:43.890 * Partial resynchronization not possible (no cached master)
[13868] 16 Oct 11:28:43.890 * Full resync from master: de143d0176fbae863acfb19241628ff395a150e7:1
[13868] 16 Oct 11:29:01.898 * MASTER <-> SLAVE sync: receiving 1551510931 bytes from master
[13868] 16 Oct 11:29:15.473 * MASTER <-> SLAVE sync: Flushing old data
[13868] 16 Oct 11:29:18.733 * MASTER <-> SLAVE sync: Loading DB in memory
[13868] 16 Oct 11:29:35.499 * MASTER <-> SLAVE sync: Finished with success
[13868] 16 Oct 11:29:40.326 # Connection with master lost.
[13868] 16 Oct 11:29:40.326 * Caching the disconnected master state.
[13868] 16 Oct 11:29:40.326 * Discarding previously cached master state.
[13868] 16 Oct 11:29:40.326 * SLAVE OF 10.86.3.175:6400 enabled (user request)
[13868] 16 Oct 11:29:40.345 # CONFIG REWRITE executed with success.
[13868] 16 Oct 11:29:41.120 * Connecting to MASTER 10.86.3.175:6400
[13868] 16 Oct 11:29:41.120 * MASTER <-> SLAVE sync started
[13868] 16 Oct 11:29:41.120 * Non blocking connect for SYNC fired the event.
[13868] 16 Oct 11:29:41.121 * Master replied to PING, replication can continue...
[13868] 16 Oct 11:29:41.121 * Partial resynchronization not possible (no cached master)
[13868] 16 Oct 11:29:41.121 * Full resync from master: de143d0176fbae863acfb19241628ff395a150e7:17244
[13868] 16 Oct 11:29:59.130 * MASTER <-> SLAVE sync: receiving 1551510931 bytes from master
[13868] 16 Oct 11:30:09.797 * MASTER <-> SLAVE sync: Flushing old data
[13868] 16 Oct 11:30:12.871 * MASTER <-> SLAVE sync: Loading DB in memory
[13868] 16 Oct 11:30:27.986 * MASTER <-> SLAVE sync: Finished with success

master log:

[13319] 16 Oct 11:27:05.917 # Server started, Redis version 2.8.17
[13319] 16 Oct 11:27:18.744 * DB loaded from disk: 12.827 seconds
[13319] 16 Oct 11:27:18.745 * The server is now ready to accept connections on port 6400
[13319] 16 Oct 11:28:43.890 * Slave asks for synchronization
[13319] 16 Oct 11:28:43.890 * Full resync requested by slave.
[13319] 16 Oct 11:28:43.890 * Starting BGSAVE for SYNC
[13319] 16 Oct 11:28:43.892 * Background saving started by pid 13344
[13344] 16 Oct 11:29:01.838 * DB saved on disk
[13344] 16 Oct 11:29:01.849 * RDB: 24 MB of memory used by copy-on-write
[13319] 16 Oct 11:29:01.897 * Background saving terminated with success
[13319] 16 Oct 11:29:15.265 * Synchronization with slave succeeded
[13319] 16 Oct 11:29:40.326 # Connection with slave 10.86.3.176:6400 lost.
[13319] 16 Oct 11:29:41.121 * Slave asks for synchronization
[13319] 16 Oct 11:29:41.121 * Full resync requested by slave.
[13319] 16 Oct 11:29:41.121 * Starting BGSAVE for SYNC
[13319] 16 Oct 11:29:41.124 * Background saving started by pid 13346
[13346] 16 Oct 11:29:59.027 * DB saved on disk
[13346] 16 Oct 11:29:59.028 * RDB: 22 MB of memory used by copy-on-write
[13319] 16 Oct 11:29:59.129 * Background saving terminated with success
[13319] 16 Oct 11:30:09.577 * Synchronization with slave succeeded