display ipv6 pathmtu vpn-instance

Function

The display ipv6 pathmtu vpn-instance command displays all IPv6 path MTU entries.

Format

display ipv6 pathmtu [ vpn-instance vpn-instance-name ] ipv6-address

display ipv6 pathmtu [ vpn-instance vpn-instance-name ] { all | dynamic | static }

Parameters

Parameter	Description	Value
vpn-instance vpn-instance-name	Specifies the name of a VPN instance. The name is used to view the path MTU entries of the specified VPN instance.	The name is a string of 1 to 31 case-sensitive characters.
ipv6-address	Specifies the path MTU entries matching with the specified IPv6 address.	-
all	Displays all path MTU entries.	-
dynamic	Displays all the dynamic path MTU entries.	-
static	Displays all the static path MTU entries.	-

Views

All views

Default Level

1: Monitoring level

Usage Guidelines

Usage Scenario

If the MTU on the outbound interface of an intermediate routing device is smaller than the MTU of the source host, the PMTU discovery mechanism can be used to discover a PMTU. The PMTU determines the size of the longest packet that can be transmitted along a path.

After the display ipv6 pathmtu command is run on a device to display information about dynamic and static PMTU entries, the device fragments packets based on a size smaller than the PMTU, and then forwards the fragments.

Precautions

If the ipv6 pathmtu command was not run to configure a PMTU for a specified IPv6 address, running the display ipv6 pathmtu command will not display any information about static PMTU entries.

Example

# Display all the path MTU entries.

<sysname> display ipv6 pathmtu all

IPv6 Destination Address     ZoneID PathMTU LifeTime(M) Type    FF
2001:db8:1::2                0      1300    9           Dynamic YES
2001:db8:2::2                0      1500    -           Static  NO
------------------------------------------------------------------
Total: 2      Dynamic: 1     Static: 1

**Table 1** Description of the **display ipv6 pathmtu** command output
Item	Description
IPv6 Destination Address	Address for the IPv6 hosts
ZoneID	Zone for the given address
PathMTU	Path MTU of the IPv6 address
LifeTime (M)	Lifetime, in minutes, with the update precision as 1 minute. For the static path MTU entry, it displays "-".
Type	Type of the IPv6 path MTU: Dynamic Static
FF	Fragment flag, the value of which indicates whether the packets on the path must carry fragment headers Y indicates that packets on the path must carry fragment headers. N indicates that packets on the path do not need to carry fragment headers.

# Display information about the path MTU of vpn1 on the local device.

<sysname> display ipv6 pathmtu vpn-instance vpn1 all

IPv6 Destination Address            ZoneID  PathMTU   LifeTime(M)  Type    FF
2001:db8:1::2                       1       1500      10           Dynamic YES
2001:db8:2::2                       1       1600      -            Static  NO
------------------------------------------------------------------------------
Total: 2      Dynamic: 1     Static: 1