Allocating IP and name on the FTD Diagnostic interface

[atsukane]

Hi there,

Does allocating an IP to diagnostic interface would cause traffic to the firewall drop completely?

Just learnt this by the hard way. Diagnostic interface is enabled by default so I just added an IP, same range as the management interface as it should.

The doc below doesn't say anything about the traffic disruption, so deployed the interface update.

Then everything stopped working for a few minutes.

Firepower Management Center Configuration Guide, Version 6.3 - Interface Overview for Firepower Threat Defense [Cisco Secure Firewall Management Center] - Cisco

[atsukane]

Apologies, there was a typo, I've managed to enter the FMC IP address in the Diagnostic interface!

BGP router IP is the FMC IP address, so I understand why BGP dropped off, but don't understand why Internet went down as well.

[MHM Cisco World]

There are two traffic 

Data and mgmt traffic 

Data traffic use defualt route 

Mgmt traffic use defualt route and can use diagnostic GW if config' I think this what will make issue here  your mgmt traffic use diagnostic gw to access internet and hence it drop and if mgmt can not access internet the data traffic will also drop.

MHM