Port Status and Basic Configuration

Jumbo Packets on the Series 2800 Switches

Terminology

Jumbo Packet: On the Series 2800 switches, an IP packet exceeding 1522 bytes in size. The maximum Jumbo packet 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 packets from external devices.

MTU (Maximum Transmission Unit): This is the maximum-size IP packet the switch can receive for Layer 2 packets inbound on a port. The switch allows jumbo packets of up to 9220 bytes.

Standard MTU: On the Series 2800 switches, an IP packet of 1522 bytes in size. (This size includes 4 bytes for the VLAN tag.)

Operating Rules

■Required Port Speed: The Series 2800 switches allow inbound and outbound jumbo packets on ports operating at speeds of 1 gigabit or higher. At lower port speeds, only standard (1522-byte or smaller) packets are allowed, regardless of the jumbo configuration.

■Flow Control: Disable flow control (the default setting) on any ports or trunks through which you want to transmit or receive jumbo packets. Leaving flow control enabled on a port can cause a high rate of jumbo drops to occur on the port.

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GVRP Operation: A VLAN enabled for jumbo traffic cannot be used to create a dynamic VLAN. A port belonging to a statically configured, jumbo- enabled VLAN cannot join a dynamic VLAN.

Port Adds and Moves: If you add a port to a VLAN that is already configured for jumbo traffic, the switch enables that port to receive jumbo traffic. If you remove a port from a jumbo-enabled VLAN, the switch disables jumbo traffic capability on the port only if the port is not currently a member of another jumbo-enabled VLAN. This same operation applies to port trunks.

■Jumbo Traffic Sources: A port belonging to a jumbo-enabled VLAN can receive inbound jumbo packets through any VLAN to which it belongs, including non-jumbo VLANs. For example, if VLAN 10 (without jumbos enabled) and VLAN 20 (with jumbos enabled) are both configured on a switch, and port 1 belongs to both VLANs, then port 1 can receive jumbo

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