Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 190)

Syntax: [no] ipv6 nd reachable-time seconds
For the seconds variable, specify a number from 0 through 3600 seconds. To restore the default time,
use the no form of this command.
NOTE
The actual reachable time will be from 0.5 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 default and maximum Ethernet MTU size is 1500 bytes. When
jumbo mode is enabled, the default Ethernet MTU size is 9216. The maximum Ethernet MTU size is
10200 for Brocade ICX 6610 devices, 10178 for Brocade ICX 6450 devices, and 10218 for other
devices.
Configuration notes and feature limitations for IPv6 MTU
• The IPv6 MTU functionality is applicable to VEs and physical IP interfaces. It applies to traffic routed
between networks.
• For ICX 7750, the IPv4 and IPv6 MTU values are the same. Modifying one also changes the value
of the other.
• For ICX 7750, the minimum IPv4 and IPv6 MTU values for both physical and virtual interfaces are
1280.
• You cannot use IPv6 MTU to set Layer 2 maximum frame sizes per interface. Enabling global
jumbo mode 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 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.
‐ For a virtual routing interface, the maximum value of the MTU is the maximum frame size
configured for the VLAN to which it is associated, minus 18 (Layer 2 MAC header + CRC).
If a maximum frame size for a VLAN is not configured, then configure the MTU based on
the smallest maximum frame size of all the ports of the VLAN that corresponds to the
virtual routing interface, minus 18 (Layer 2 MAC header + CRC).
Changing the IPv6 MTU
You can configure the IPv6 MTU on individual interfaces. For example, to configure the MTU on
Ethernet interface 3/1 as 1280 bytes, enter the following commands.
device(config)#interface ethernet 3/1
device(config-if-e1000-3/1)#ipv6 mtu 1280
IPv6 MTU
190 FastIron Ethernet Switch Layer 3 Routing Configuration Guide
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