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Configuration Guide - IP Service

CloudEngine 12800 and 12800E V200R005C00

This document describes the configurations of IP Service, including IP address, ARP, DHCP, DNS, IP performance optimization, IPv6, DHCPv6, and IPv6 DNS.
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Setting the Aging Time of Dynamic PMTU

Setting the Aging Time of Dynamic PMTU


When the device functions as a source node and sends packets to a destination node, the device dynamically negotiates the PMTU with the destination node according to the IPv6 MTU values of interfaces and fragments packets based on the PMTU. After the PMTU ages out, the dynamic PMTU is deleted. The source node dynamically renegotiates the PMTU with the destination node.


When both static and dynamic PMTUs are configured, only static PMTU takes effect. Static PMTU entries never age.

The interface MTU, IPv6 interface MTU, and PMTU are valid only for packets generated on the device, not for packets forwarded by the host.

A switch can receive ICMPv6 error packets that are sent from other devices and learns the path MTU according to the received ICMPv6 error packets.


  1. Run system-view

    The system view is displayed.

  2. (Optional) Configure the IPv6 MTU for an interface.

    1. Run interface interface-type interface-number

      The specified interface view is displayed.

    2. (For Ethernet interfaces) Run undo portswitch

      The interface is switched to Layer 3 mode.

      By default, an Ethernet interface works in Layer 2 mode.

      The command fails if any Layer 2 configuration exists on the interface. In such a case, clear the Layer 2 configurations on the interface before running the undo portswitch command.

      You can run the undo portswitch batch interface-type { interface-number1 [ to interface-number2 ] } &<1-10> command in the system view to switch the working mode of multiple Ethernet interfaces in batches.

    3. Run ipv6 enable

      The IPv6 function is enabled on the interface.

      By default, the IPv6 function is disabled on an interface.

    4. Run ipv6 mtu mtu

      The MTU of IPv6 packets on an interface is set.

      By default, the MTU of IPv6 packets on an interface is 1500 bytes.

      After the MTU value is changed, run the shutdown and undo shutdown commands or the restart (interface view) command to restart the interface and allow the changes to take effect.
    5. Run quit

      The system view is displayed.

  3. Run ipv6 pathmtu age age-time

    The aging time is set for dynamic PMTU entries.

    By default, the aging time of dynamic PMTU entries is 10 minutes.

  4. Run commit

    The configuration is committed.

Updated: 2019-04-18

Document ID: EDOC1100039535

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