System information

10-19

Port Status and Basic Configuration

Jumbo Frames

The Maximum Transmission Unit (MTU) is the maximum size IP frame the

switch can receive for Layer 2 frames inbound on a port. The switch drops any

inbound frames larger than the MTU allowed on the port. On ports operating

at 10 Mbps or 100 Mbps, the MTU is fixed at 1522 bytes. However, ports

operating at 1 Gbps or 10 Gbps speeds accept forward frames of up to 9220

bytes (including four bytes for a VLAN tag) when configured for jumbo traffic.

You can enable inbound jumbo frames on a per-VLAN basis. That is, on a VLAN

configured for jumbo traffic, all ports belonging to that VLAN and operating

at 1 Gbps or 10 Gbps allow inbound jumbo frames of up to 9220 bytes.

(Regardless of the mode configured on a given jumbo-enabled port, if the port

is operating at only 10 Mbps or 100 Mbps, only frames that do not exceed 1522

bytes are allowed inbound on that port.)

Terminology

Jumbo Frame: An IP frame exceeding 1522 bytes in size. The maximum

Jumbo frame size is 9220 bytes. (This size includes 4 bytes for the VLAN

tag.)

Jumbo VLAN: A VLAN configured to allow inbound jumbo traffic. All ports

belonging to a jumbo and operating at 1 Gbps or higher can receive jumbo

frames from external devices.

MTU (Maximum Transmission Unit): This is the maximum-size IP frame

the switch can receive for Layer 2 frames inbound on a port. The switch

allows jumbo frames of up to 9220 bytes.

Standard MTU: An IP frame of 1522 bytes in size. (This size includes 4 bytes

for the VLAN tag.)

Feature Default Menu CLI Web

display VLAN jumbo status n/a — 10-22 —

configure jumbo VLANs Disabled — 10-24 —