KB.15.15

• Any port operating at 1 Gbps or higher can transmit outbound jumbo frames through any

VLAN, regardless of the jumbo configuration. The VLAN is not required to be jumbo-enabled,

and the port is not required to belong to any other, jumbo-enabled VLANs. This can occur in

situations where a non-jumbo VLAN includes some ports that do not belong to another,

jumbo-enabled VLAN and some ports that do belong to another, jumbo-enabled VLAN. In this

case, ports capable of receiving jumbo frames can forward them to the ports in the VLAN that

do not have jumbo capability, as shown in Figure 85.

Figure 85 Forwarding jumbo frames through non-jumbo ports

Jumbo frames can also be forwarded out non-jumbo ports when the jumbo frames received

inbound on a jumbo-enabled VLAN are routed to another, non-jumbo VLAN for outbound

transmission on ports that have no memberships in other, jumbo-capable VLANs. Where either

of the above scenarios is a possibility, the downstream device must be configured to accept

the jumbo traffic. Otherwise, this traffic will be dropped by the downstream device.

• If a switch belongs to a meshed domain, but does not have any VLANs configured to support

jumbo traffic, the meshed ports on that switch drop any jumbo frames they receive from other

devices. In this regard, if a mesh domain includes any HP

1600M/2400M/2424M/4000M/8000M switches, along with the switches covered in this

guide configured to support jumbo traffic, only the switches covered in this guide receive

jumbo frames. The other switch models in the mesh will drop such frames. For more information

on switch meshing, see the Advanced Traffic Management Guide.

Jumbo frame maximum size

The maximum frame size for jumbos is supported with the following proprietary MIB object:

hpSwitchMaxFrameSize OBJECT-TYPE

This is the value of the global max-frame-size supported by the switch. The default value is set

to 9216 bytes.

Jumbo IP MTU

The IP MTU for jumbos is supported with the following proprietary MIB object:

hpSwitchIpMTU OBJECT-TYPE

This is the value of the global jumbos IP MTU (or L3 MTU) supported by the switch. The default

value is set to 9198 bytes (a value that is 18 bytes less than the largest possible maximum frame

size of 9216 bytes.) This object can be used only in switches that support max-frame-size and

ip-mtu configuration.

194 Port Traffic Controls