display ipv6 pathmtu

Function

The display ipv6 pathmtu command displays all IPv6 PMTU entries.

Format

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

Parameters

Parameter	Description	Value
vpn-instance vpn-instance-name	Displays PMTU entries with a specified IPv6 VPN instance.	The value is a string of 1 to 31 case-sensitive characters, spaces not supported. In addition, the VPN instance name must not be _public_. When double quotation marks are used around the string, spaces are allowed in the string.
ipv6-address	Displays PMTU entries with a specified IPv6 address.	The address is a 32-bit hexadecimal number, in the format of X:X:X:X:X:X:X:X.
all	Displays all PMTU entries.	-
dynamic	Displays all dynamic PMTU entries.	-
static	Displays all static PMTU entries.	-

Views

All views

Default Level

1: Monitoring level

Task Name and Operations

Task Name	Operations
ip-stack	read

Usage Guidelines

Usage Scenario

When the MTU of the outbound interface on an intermediate device is smaller than the MTU of the source host, the PMTU discovery mechanism is used to determine the maximum size of packets that can be transmitted on the path, that is, a PMTU.

To check dynamic and static PMTU entries, run the display ipv6 pathmtu command. The Router fragments packets into a size smaller than a set PMTU and forwards the fragments.

Precautions

If no PMTU is set using the ipv6 pathmtu command, no static PMTU entries are displayed in the display ipv6 pathmtu command output.

Example

The actual command output varies according to the device. The command output here is only an example.

# Display all PMTU entries.

<HUAWEI> display ipv6 pathmtu all
Total: 2        Dynamic: 1      Static: 1
- ----------------------------------------------------------------------------
IPv6 Destination Address                 ZoneID  PathMTU  LifeTime(M)  Type     FF
2001:DB8::2                              0       1300     9            Dynamic  NO
2001:DB8::1                              0       1500     -            Static   NO

# Display PMTU entries of vpn1.

<HUAWEI> display ipv6 pathmtu vpn-instance vpn1 all
Total: 2        Dynamic: 1      Static: 1
- ----------------------------------------------------------------------------
IPv6 Destination Address                 ZoneID  PathMTU  LifeTime(M)  Type     FF
2001:DB8::4                               1      1500     10           Dynamic  NO
2001:DB8::3                               1      1600     -            Static   NO

**Table 1** Description of the **display ipv6 pathmtu** command output
Item	Description
IPv6 Destination Address	IPv6 destination address.
ZoneID	Zone of an IPv6 address.
PathMTU	PMTU of an IPv6 address.
LifeTime(M)	Remaining lifetime of a dynamic PMTU entry, in minutes. This field displays a hyphen (-) for a static PMTU entry.
Type	Type of a PMTU: Dynamic. Static.
Dynamic	Number of dynamic PMTU entries.
Static	Number of static PMTU entries.
FF	Fragmentation flag: YES: Packets are fragmented, and a fragment header is added to a packet. NO: Packets are not fragmented.
Total	Total number of PMTU entries.