Why does ONTAP initiate a connection on a port other than 4045 for for NLM callbacks?
Applies to
- ONTAP 9
- UNIX or UNIX-like operating system
- NFSv3
Answer
- Clients request NLM locks with requests sent to ONTAP on port 4045.
- If a blocking lock cannot be granted immediately, ONTAP will later send a callback to the client when the lock is granted.
- The callback will be done from ONTAP to the client using a port discovered using the port mapper.
- Packet trace snippet indicating NLM is being blocked:
1478 2022-08-04 07:07:34.920384 xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx NLM V4 LOCK Call (Reply In 1479) FH:0x91a3284f 1479 2022-08-04 07:07:34.920835 xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx NLM V4 LOCK Reply (Call In 1478) NLM_BLOCKED
- Packet trace snippet confirming which port is used by the client:
9 2022-08-04 07:07:10.362505 1xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx Portmap V2 GETPORT Call (Reply In 11) NLM(100021) V:4 TCP 11 2022-08-04 07:07:10.363195 xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx Portmap V2 GETPORT Reply (Call In 9) Port:34726
Additional Information
The NLM port used by ONTAP can be configured using
nfs option modify -nlm-port
.