Gigabit Ethernet has an auto-negotiation procedure that is more extensive than that of 10/100 Mbps Ethernet (per Gigabit auto-negotiation specification IEEE 802.3z-1998). The Gigabit auto-negotiation negotiates flow control, duplex mode, and remote fault information. You must either enable or disable link negotiation on both ends of the link. Both ends of the link must be set to the same value or the link will not connect.
If either device does not support Gigabit auto-negotiation, disabling Gigabit auto-negotiation forces the link up.
Troubleshooting a Duplex Mismatch with Cisco Devices
When troubleshooting connectivity issues with Cisco switches or routers, verify that the Sensor and the switch/routers are using a valid configuration. The show intfport <port> command on the Sensor CLI will help reveal errors.
Sometimes, there are duplex inconsistencies between Trellix IPS and the switch port. Symptoms include poor port performance and frame check sequence (FCS) errors that increment on the switch port. To troubleshoot this issue, manually configure the switchport to 100 Mbps, half-duplex. If this action resolves the connectivity problems, you might be running into this issue. Contact Cisco's TAC for assistance.
Use the following commands to verify fixed interface settings on some Cisco devices that connect to Sensors: