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Monitoring TCP PMTU Information
Purpose
Display PMTU information.
Action
To display PMTU information:
host1#show tcp path-mtu-discovery
TCP PMTU Discovery is ENABLED
Administrative Minimum MTU: 512
Administrative Maximum MTU: 65535
Timer 1: 10 minutes
Timer 2: 2 minutes
Black Hole Detect Threshold: 0 retransmissions
# ICMP TooBigs: 0
# ICMP TooBigs for unk. connections: 0Meaning
Table 26 lists the show tcp path-mtu-discovery command output fields.
Table 26: show tcp path-mtu-discovery Output Fields
Field Name | Field Description |
|---|---|
TCP PMTU Discovery | State of the PMTUD functions (ENABLED or DISABLED) |
Administrative Minimum MTU | Administrative minimum PMTU that is supported or none if there is no minimum |
Administrative Maximum MTU | Administrative maximum PMTU that is supported or none if there is no maximum |
Timer 1 | Value of timer 1 in minutes |
Timer 2 | Value of timer 2 in minutes |
Black Hole Detect Threshold | Number of retransmissions allowed before TCP/PMTUD assumes that there is a black hole and attempts to reduce impact in the MSS |
# ICMP TooBigs | Number of ICMP Too Big messages that have been received |
# ICMP TooBigs for unk. connections | Number of ICMP Too Big messages that have been received which were not for a valid connection |
