Restrictions for TCP Keepalive Timer
The TCP Keepalive timer parameters can be configured only on vty and TTY applications.
The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
The TCP Keepalive timer parameters can be configured only on vty and TTY applications.
The TCP Keepalive Timer feature provides a mechanism to identify dead connections.
When a TCP connection on a routing device is idle for too long, the device sends a TCP keepalive packet to the peer with only the Acknowledgment (ACK) flag turned on. If a response packet (a TCP ACK packet) is not received after the device sends a specific number of probes, the connection is considered dead and the device initiating the probes frees resources used by the TCP connection.
The following parameters are used to configure TCP keepalive:
TCP Keepalive idle time: The value of this parameter indicates the time for which a TCP connection can be idle before the connection initiates keepalive probes.
TCP Keepalive retries: The value of this parameter is the number of unacknowledged probes that a device can send before declaring the connection as dead and tearing it down.
TCP Keepalive interval: The time between subsequent probe retries.
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable Example:
|
Enables privileged EXEC mode.
|
Step 2 |
configure terminal Example:
|
Enables global configuration mode. |
Step 3 |
ip tcp keepalive interval seconds Example:
|
Configures the keepalive interval. |
Step 4 |
ip tcp keepalive retries number-of-retries Example:
|
Configures the number of unacknowledged probes that can be sent before declaring the connection as dead. |
Step 5 |
end Example:
|
Exits global configuration mode and returns to privileged EXEC mode. |
Step 6 |
show running-config Example:
|
(Optional) Displays the running configuration. |
The following example shows how to configure TCP keepalive parameters.
Device> enable
Device# configure terminal
Device(config)# ip tcp keepalive interval 2
Device(config)# ip tcp keepalive retries 5
Device(config)# end
The following is a sample output of the show running-config command:
Device# show running-config
ip tcp keepalive retries 5
ip tcp keepalive interval 2
Standard/RFC |
Title |
---|---|
RFC 793 |
|
RFC 1191 |
|
RFC 1323 |
|
RFC 2018 |
|
RFC 2581 |
|
RFC 3168 |
The Addition of Explicit Congestion Notification (ECN) to IP |
RFC 3782 |
|
RFC 4022 |
Management Information Base for the Transmission Control Protocol (TCP) |
Description |
Link |
---|---|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
This table provides release and related information for the features explained in this module.
These features are available in all the releases subsequent to the one they were introduced in, unless noted otherwise.
Release |
Feature |
Feature Information |
---|---|---|
Cisco IOS XE Fuji 16.8.1a |
TCP Keepalive Timer |
The TCP Keepalive Timer feature introduces the capability to identify dead connections between multiple routing devices. The following command was introduced or modified by this feature: ip tcp keepalive . |
Use the Cisco Feature Navigator to find information about platform and software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn.