Cisco Cisco Firepower Management Center 4000

In the 

 field, type a maximum transmission unit (MTU), which designates the largest size packet 

allowed.

The range within which you can set the MTU can vary depending on the FireSIGHT System device 
model and the interface type. See 

information.

Click 

.

Your changes are saved. Note that your changes do not take effect until you apply the device 
configuration; see 

 for more information.

Any

When you change the maximum transmission unit (MTU) on an interface or inline set, the following 
capabilities may be affected:

traffic inspection, including application awareness and control, URL filtering, intrusion detection 
and prevention, and connection logging

traffic flow, including switching, routing, and related functionality

link state

The manner and duration of network traffic interruption depends on the interface type and how your 
devices are configured and deployed.

Note also that for Sourcefire Software for  X-Series, you configure the interface MTU using the 
Sourcefire Software for  X-Series CLI. See the Sourcefire Software for  X-Series Installation Guide for 
more information.

Because the system automatically trims 18 bytes from the configured MTU value, any value below 1298 
does not comply with the minimum IPv6 MTU setting of 1280, and any value below 594 does not comply 
with the minimum IPv4 MTU setting of 576. For example, the system automatically trims a configured 
value of 

576

 to 

558

.

The following table lists MTU configuration ranges for managed devices.

Control, Protection

Series 2, except 3D6500, 3D9900

576-1518 (all interfaces, inline sets)

3D6500, 3D9900, virtual

576-9018 (all interfaces, inline sets)

Series 3

576-9234 (management interface)

 

576-10172 (inline sets)

 

576-9922 (all others)