Brocade Communications Systems 6650 IPv6 MTU, Configuring reachable time for remote IPv6 nodes

5 IPv6 MTU

Configuring reachable time for remote IPv6 nodes

You can configure the duration (in seconds) that a router considers a remote IPv6 node reachable. By default, a router interface uses the value of 30 seconds.

The router advertisement messages sent by a router interface include the amount of time specified by the ipv6 nd reachable-timecommand so that nodes on a link use the same reachable time duration. By default, the messages include a default value of 0.

Brocade does not recommend configuring a short reachable time duration, because a short duration causes the IPv6 network devices to process the information at a greater frequency.

For example, to configure the reachable time of 40 seconds for Ethernet interface 1/1/1, enter the following commands.

Brocade(config)#interface ethernet 1/1/1

Brocade(config-if-e10000-1/1/1)#ipv6 nd reachable-time 40

Syntax: [no] ipv6 nd reachable-time <seconds>

For the <seconds> parameter, specify a number from 0 – 3600 seconds. To restore the default time, use the no form of this command.

NOTE

The actual reachable time will be from .5 to 1.5 times the configured or default value.

IPv6 MTU

The IPv6 maximum transmission unit (MTU) is the maximum length of an IPv6 packet that can be transmitted on a particular interface. If an IPv6 packet is longer than an MTU, the host that originated the packet fragments the packet and transmits its contents in multiple packets that are shorter than the configured MTU.

By default, in non-jumbo mode, the maximum Ethernet MTU size is 1500 bytes. When jumbo is enabled, the default maximum Ethernet MTU size is 10200.

Configuration notes and feature limitations for IPv6 MTU

•The IPv6 MTU command is applicable to VEs and physical IP interfaces. It applies to traffic routed between networks.

•You cannot use this command to set Layer 2 maximum frame sizes per interface. The global jumbo command causes all interfaces to accept Layer 2 frames.

•For non-jumbo mode, you can configure an IPv6 MTU greater than 1500 bytes, although the default remains at 1500 bytes. The value of the MTU you can define depends on the following:

•For a physical port, the maximum value of the MTU is the equal to the maximum frame size of the port minus 18 (Layer 2 MAC header + CRC).

•If a the size of a jumbo packet received on a port is equal to the maximum frame size – 18 (Layer 2 MAC header + CRC) and if this value is greater than the outgoing port’s IPv4/IPv6 MTU, then it will be forwarded in the CPU.

136	Brocade ICX 6650 Administration Guide
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