R0106-HP MSR Router Series Layer 3 - IP Services Configuration Guide(V7)

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Configuring path MTU discovery
Configuring the interface MTU
IPv6 routers do not support packet fragmentation. If the size of a packet exceeds the MTU of the output
interface, the router discards the packet and sends a packet too big message to the source host. The
source host fragments the packet according to the MTU. To avoid this situation, configure a proper
interface MTU.
To configure the interface MTU:
Ste
p
Command Remarks
1. Enter system view.
system-view
N/A
2. Enter interface view.
interface interface-type
interface-number
N/A
3. Configure the interface MTU.
ipv6 mtu mtu-size
By default, no interface MTU is
configured.
Configuring a static path MTU for an IPv6 address
You can configure a static path MTU for an IPv6 address. Before sending a packet to the IPv6 address,
the device compares the MTU of the output interface with the static path MTU. If the packet exceeds the
smaller one of the two values, the device fragments the packet according to the smaller value. After
sending the fragmented packets, the device dynamically finds the path MTU to a destination host (see
"IPv6 path MTU discovery")
.
To configure a static path MTU for a destination IPv6 address:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Configure a static path MTU
for a destination IPv6 address.
ipv6 pathmtu [ vpn-instance
vpn-instance-name ] ipv6-address
value
No static path MTU is configured
for any IPv6 address by default.
Configuring the aging time for dynamic path MTUs
After the device dynamically finds the path MTU to a destination host (see "IPv6 path MTU discovery"),
it sends packets to the destination host based on the path MTU and starts an aging timer. When the
aging timer expires, the device removes the dynamic path MTU and finds the path MTU again.
The aging time is invalid for a static path MTU.
To configure the aging time for dynamic path MTUs:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Configure the aging time for
dynamic path MTUs.
ipv6 pathmtu age age-time The default setting is 10 minutes.