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
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.)
Jumbo
1
on All VLANs
Jumbo
1
On All But
Source VLAN
1518
9216
1518
0
0
0
1518
9216
n/a
2
1464 54
9162 54
1464 54
Tagged
Non-Jumbo
Jumbo
1
on All VLANs
Jumbo
1
On All But
Source VLAN
1522
9220
1522
4
4
4
1522
9218
n/a
2
1468 54
9164 54
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.
B-93
