Packet flow from client to web server
1. The client computer requests a connection from 10.11.101.10 to 172.20.120.130.
2. The default route on the client computer recognizes 10.11.101.100 (the cluster IP address) as the gateway to the external network where the web server is located.
3. The client computer issues an ARP request to 10.11.101.100.
4. The primary unit intercepts the ARP request, and responds with the internal virtual MAC address (MAC_V_int) which corresponds to its IP address of 10.11.101.100.
5. The client’s request packet reaches the primary unit internal interface.
| IP address | MAC address |
Source | 10.11.101.10 | MAC_Client |
Destination | 172.20.120.130 | MAC_V_int |
6. The primary unit decides that the subordinate unit should handle this packet, and forwards it to the subordinate unit internal interface. The source MAC address of the forwarded packet is changed to the actual MAC address of the primary unit internal interface.
| IP address | MAC address |
Source | 10.11.101.10 | MAC_P_int |
Destination | 172.20.120.130 | MAC_S_int |
7. The subordinate unit recognizes that the packet has been forwarded from the primary unit and processes it.
8. The subordinate unit forwards the packet from its external interface to the web server.
| IP address | MAC address |
Source | 172.20.120.141 | MAC_S_ext |
Destination | 172.20.120.130 | MAC_Server |
9. The primary unit forwards further packets in the same session to the subordinate unit.
10. Packets for other sessions are load balanced by the primary unit and either sent to the subordinate unit or processed by the primary unit.