Both the DR and Nat modes inevitably have a problem: LVs and RS must be in the same VLAN, otherwise LVS cannot be the gateway for Rs.
The two problems that arise are:
1, the same VLAN restrictions cause operation is inconvenient, RS cross VLAN can not access.
2. The level expansion of LVS is restricted. When RS expands horizontally, one day its single-point LVS will become a bottleneck.
Full-nat from this, the solution is LVS and Rs cross-VLAN problem, and after the cross-VLAN problem solved, LVS and RS no longer have a dependency on the VLAN, you can do multiple LVS corresponding to multiple RS, solve the problem of horizontal expansion.
Full-nat the main improvement over NAT is that, on the basis of Snat/dnat, plus another conversion, the conversion process is as follows:
In the process of transferring the package from LVs to RS, the source address is replaced with the LVS intranet IP from the client IP.
Inter-network IP can communicate across VLANs through multiple switches.
When RS finishes processing the received packet, it returns the packet back to the LVS intranet IP, which is not restricted to VLANs.
After the LVS receives the package, the NAT mode modifies the source address, then the target address from the RS packet is changed from the LVS intranet IP to the client IP.
The main idea of Full-nat is to change the communication between the gateway and its lower machine to the normal network communication, which solves the problem of cross-VLAN. In this way, the deployment of LVS and RS will no longer have any restrictions on VLANs, greatly improving the convenience of operational deployment.