Enabling jumbo frames to increase the mirroring path MTU

On 1-Gbps and 10-Gbps ports in the mirroring path, you can reduce the number of dropped frames by enabling jumbo frames on all intermediate switches and routers. (The MTU on the switches covered by this manual is 9220 bytes for frames having an 802.1Q VLAN tag, and 9216 bytes for untagged frames.)

Table 26: Maximum frame sizes for mirroring
 

Frame type configuration

Maximum frame size

VLAN tag

Frame mirrored to local port

Frame mirrored to remote port

Data

Data

IPv4 header

Untagged

Non-jumbo (default config.)

1518

0

1518

1464

54

Jumbo on all VLANs

9216

0

9216

9162

54

Jumbo11 On all but source VLAN

1518

0

n/a

1464

54

Tagged

Non-jumbo

1522

4

1522

1468

54

Jumbo11 on all VLANs

9220

4

9218

9164

54

Jumbo11 On all but source VLAN

1522

4

n/a22

1468

54

1

Jumbo frames are allowed on ports operating at or above 1 Gbps

2

For local mirroring, a non-jumbo configuration on the source VLAN dictates an MTU of 1518 bytes for untagged frames, and an MTU of 1522 for tagged frames, regardless of the jumbo configuration on any other VLANs on the switch.