Unexpected File Transfer Protocol Server Behavior During Unified ISSU

You can perform the unified ISSU operation even when the FTP server is enabled on the router. However, no file transfer process, such as uploading or downloading of files, creating of directories, or removing of files, can be in progress to enable the unified ISSU operation to complete successfully.

When you issue the issu initialize command, unified ISSU checks for open FTP connections or active file transfer sessions. At this stage, existing connections are not terminated and new connections can also be established. When you issue the issu start command, all FTP connections, including data and control connections, are disconnected. Although the listening port is still available at this stage, any attempt to create a new connection and incomplete file operations on existing connections fail with an appropriate error message from the FTP server.

The issu start command is not executed if file transfer operations are in progress. You must issue the ftp-server flush command to forcibly terminate the file transfer process. When you are prompted to confirm, type y to confirm to close all active file transfer jobs.

Caution: Because using the ftp-server flush command causes a forced and ungraceful termination of all file transfer jobs that are in progress to start the unified ISSU process, use it only when it is absolutely necessary. We recommend that you wait for file transfer operations that are in progress to complete gracefully before you perform unified ISSU, if your situation enables you to do so.

The following example shows the output of the show ftp-server command in a scenario where FTP server is enabled, but no open file transfer connections exist.

host1#show ftp-server
FTP Server state: enabled, 0 open connections
Statistics since server was last started:
        attempts: 3
        failed hosts: 0
        failed users: 0
Statistics since last system reload:
        attempts: 3
        failed hosts: 0
        failed users: 0

To display detailed information about unified ISSU status and warnings in addition to criteria required for unified ISSU and whether the router hardware and software meet the required criteria, issue the show issu detail command.

host1#show issu detail
ISSU state:       idle
ISSU description: ISSU is currently idle
criteria met:     No, upgrade error(s) found
running release:  dtnguyen.rel
armed release:    dtnguyen.rel
#                       ISSU Criteria Summary                           Met
--   ------------------------------------------------------------   -----------
1    In-Service Software Upgrade ready?                             Yes
2    High-Availability ready?                                       No
3    Line modules ready?                                            Conditional
4    Configuration conversion support ready?                        Yes
5    CLI sessions ready?                                            Yes
6    Routing applications ready?                                    Yes
7    Protocol timers ready?                                         Yes

The following example shows a case when a few clients are connected to the FTP server, and the FTP ISSU state becomes conditional. However, unified ISSU begins without any error. All existing connections are dropped when you issue the issu start command and the upgrade runs.

host1#show ftp-server
FTP Server state: enabled, 1 open connections Statistics since server was last started: attempts: 3 failed hosts: 0 failed users: 0 Statistics since last system reload: attempts: 3 failed hosts: 0 failed users: 0
host1#show issu detail
ISSU state:       idle
ISSU description: ISSU is currently idle
criteria met:     No, upgrade error(s) found
running release:  dtnguyen.rel
armed release:    dtnguyen.rel
#                       ISSU Criteria Summary                           Met
--   ------------------------------------------------------------   -----------
1    In-Service Software Upgrade ready?                             Yes
2    High-Availability ready?                                       No
3    Line modules ready?                                            Conditional
4    Configuration conversion support ready?                        Yes
5    CLI sessions ready?                                            Yes
6    Routing applications ready?                                    Conditional
->   Criteria: There are open FTP connections                       Conditional
     Impact: Open connections will be disconnected during ISSU
     process
     Remedy: Close all FTP sessions
     Reporting slot: 7
7    Protocol timers ready?                                         Yes

The following example shows when an ongoing file transfer operation is detected during the initialization phase or validation phase. In this case, the prerequisite verification that unified ISSU performs fails. Unified ISSU does not proceed until the active file transfer operations are terminated. Issue the ftp-server flush command to forcibly terminate all FTP sessions.

host1#show ftp-server
FTP Server state: enabled, 1 open connections
Statistics since server was last started:
        attempts: 3
        failed hosts: 0
        failed users: 0
Statistics since last system reload:
        attempts: 3
        failed hosts: 0
        failed users: 0

host1#show issu detail
ISSU state:       idle
ISSU description: ISSU is currently idle
criteria met:     No, upgrade error(s) found
running release:  dtnguyen.rel
armed release:    dtnguyen.rel
#                       ISSU Criteria Summary                           Met
--   ------------------------------------------------------------   -----------
1    In-Service Software Upgrade ready?                             Yes
2    High-Availability ready?                                       No
3    Line modules ready?                                            Conditional
4    Configuration conversion support ready?                        Yes
5    CLI sessions ready?                                            Yes
6    Routing applications ready?                                    No
->   Criteria: FTP file transfer is in progress                     No         
     Impact: ISSU cannot be performed when file transfer is in pr              
     ogress                                                                    
     Remedy: Abort transfer with "ftp-server flush" or wait until 
     transfer is done                           
     Reporting slot: 7                                                         
7    Protocol timers ready?                                         Yes

host1#ftp-server flush
This command will terminate all FTP sessions, continue? [confirm]
host1#

New FTP connections are not allowed and all existing FTP connections are dropped after the unified ISSU process begins. Also, no remote file operations are allowed while unified ISSU is in progress. If unified ISSU is aborted, FTP server is returned to the state in which it was before unified ISSU was started.

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