LogFAQs > #975765144

About a month ago, we upgraded the software on our Fortinet firewalls. After that, DHCP traffic wasn't going through properly at one of our data centers. I thought it was 100% a Fortinet issue since that's the only change that was made, and it doesn't make sense for only DHCP traffic to be dropped by any networking device.

Turns out the firewalls were still sending the traffic to the downstream core Cisco Nexus switches, but one of those Cisco Nexus switches was just dropping all real DHCP traffic that passed through it. If we generated a fake DHCP traffic with iperf, it worked. Real DHCP traffic was getting dropped. Cisco couldn't provide a solution through troubleshooting, so they recommended that we reboot the switch. We rebooted that core switch tonight and boom, the problem isn't happening any more.

This will be one that all of our network engineers will have to keep in mind because we periodically fail back and forth between our two data centeres.