Enabling PMTU Discovery

Use the tcp path-mtu-discovery command to enable PMTU discovery on the active virtual router.

tcp path-mtu-discovery

• Use to enable and configure path MTU discovery on the virtual router.
• Issue the command without any keywords to enable path MTU discovery.
• Issue the age-timer keyword to set the time (minutes) that TCP waits before attempting to increase the path MTU after receiving an ICMP Too Big message or after previously increasing the PMTU successfully (minutes2). The range of these two timers is 1–30 minutes. The timer defaults to 10 minutes.
• Issue the age-timer infinite keyword to disable PMTU aging functions.
• Example 1—Enables path MTU discovery

  host1:VR1(config)#tcp path-mtu-discovery

• Example 2—Sets path MTU discovery age timers differently

  host1:VR1(config)#tcp path-mtu-discovery age-timer 20 15

• Example 3—Sets path MTU discovery age timers to the same value
  (5 minutes)

  host1:VR1(config)#tcp path-mtu-discovery age-timer 5

• Example 4—Disables path MTU discovery age timers

  host1:VR1(config)#tcp path-mtu-discovery age-timer infinite

• Use the no version with a keyword to return the value to its default. Issue the no version without any keywords to disable path MTU discovery on the virtual router.
• See tcp path-mtu-discovery

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