Dell SmartFabric OS10 User Guide Release 10.5.3

LACP fallback in non-VLT network

In a non-VLT network, LACP fallback enables rebooting of ToR or server that is connected to the switch through normal LACP. The other end of the switch is connected to a DHCP/PXE server, as shown in the following figure:

In the above scenario, LACP fallback works as follows:

1. The ToR/server boots
2. The switch detects the link that is up and checks fallback enabled status. If fallback is enabled, the device waits for the time-out period for any LACP BPDUs. If there are no LACP BPDUs received within the time period, then the port-channel enters into fallback mode and adds the first operationally UP port to the port channel instead of placing it in an inactive state.
3. Now the ToR/server has one port up and active. The active port sends packets to the DHCP/PXE server.
4. After receiving response from the DHCP server, the ToR/server boots from the TFTP/NFS server.
5. When the ToR/server is fully loaded with the boot image and configurations, the server starts sending LACP PDUs.
6. When the switch receives LACP PDUs from ToR/server, the device comes out of the fallback mode and activates the port-channel through normal LACP process.