Monitoring and Analyzing Switch Operation

Traffic Mirroring

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 maximum transmission unit—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.) For information on configuring the switch for jumbo frames, refer to “Configuring Jumbo Frame Operation” on page 13-32.

Table B-2. Maximum Frame Sizes for Mirroring

 

Frame Type

Maximum

 

VLAN

Frame Mirrored

Frame Mirrored to

 

Configuration

Frame

 

Tag

to Local Port

Remote Port

 

 

Size

 

 

 

 

 

 

 

 

 

Data

Data

IPv4 Header

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Non-Jumbo

1518

 

0

1518

1464

54

Untagged

(default config.)

 

 

 

 

 

 

Jumbo1 On All But

1518

 

0

n/a2

1464

54

 

Jumbo1 on All VLANs

9216

 

0

9216

9162

54

 

Source VLAN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Tagged

Non-Jumbo

1522

 

4

1522

1468

54

Jumbo1 On All But

1522

 

4

n/a2

1468

54

 

Jumbo1 on All VLANs

9220

 

4

9218

9164

54

 

Source VLAN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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

2For 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.

B-93