Ip Fragmentation Within A Vlan - Extreme Networks ExtremeWare XOS Guide Manual

Configuring Slots and Ports on a Switch
ExtremeWare XOS supports the fragmenting of IP packets. If an IP packet originates in a local network
that allows large packets and those packets traverse a network that limits packets to a smaller size, the
packets are fragmented instead of discarded.
This feature is designed to be used in conjunction with jumbo frames. Frames that are fragmented are
not processed at wire-speed within the switch fabric.
NOTE
Jumbo frame-to-jumbo frame fragmentation is not supported. Only jumbo frame-to-normal frame fragmentation is
supported.
To configure VLANs for IP fragmentation:
1 Enable jumbo frames on the incoming port.
NOTE
If you are working with the BlackDiamond 8800 family of switches or a Summit X450, you must enable jumbo
frames for the entire switch.
2 Add the port to a VLAN.
3 Assign an IP address to the VLAN.
4 Enable ipforwarding on the VLAN.
5 Set the MTU size for the VLAN, using the following command:
configure ip-mtu <mtu> vlan <vlan_name>
The ip-mtu value ranges between 1500 and 9216, with 1500 the default.
NOTE
To set the MTU size greater than 1500, all ports in the VLAN must have jumbo frames enabled.

IP Fragmentation within a VLAN

ExtremeWare XOS supports IP fragmentation within a VLAN. This feature does not require you to
configure the MTU size. To use IP fragmentation within a VLAN:
1 Enable jumbo frames on the incoming port.
2 Add the port to a VLAN.
3 Assign an IP address to the VLAN.
4 Enable ipforwarding on the VLAN.
If you leave the MTU size configured to the default value, when you enable jumbo frame support on a
port on the VLAN you will receive a warning that the ip-mtu size for the VLAN is not set at maximum
jumbo frame size. You can ignore this warning if you want IP fragmentation within the VLAN, only.
However, if you do not use jumbo frames, IP fragmentation can only be used for traffic that stays
within the same VLAN. For traffic that is set to other VLANs, to use IP fragmentation, all ports in the
VLAN must be configured for jumbo frame support.
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ExtremeWare XOS 11.3 Concepts Guide