3.1. The NAT LVS Cluster

3.1. The NAT LVS Cluster

The NAT topology allows for great latitude in utilizing existing hardware, but it is limited in its ability to handle large loads due to the fact that all packets going into and coming out of the cluster pass through the LVS router.

Network Layout

The topology for an LVS cluster utilizing NAT routing is the easiest to configure from a network layout perspective because the cluster needs only one access point to the public network. The real servers pass all requests back through the LVS router so they are on their own private network.


The NAT topology is the most flexible in regards to cluster hardware because the real servers do not need to be Linux machines to function correctly in the cluster. In a NAT cluster, each real server only needs one NIC since it will only be responding to the LVS router. The LVS routers, on the other hand, need two NICs each to route traffic between the two networks. Because this topology creates a network bottleneck at the LVS router, gigabit Ethernet NICs can be employed on each LVS router to increase the bandwidth the LVS routers can handle. If gigabit Ethernet is employed on the LVS routers, any switch connecting the real servers to the LVS routers must have at least two gigabit Ethernet ports to handle the load efficiently.


Because the NAT topology requires the use of iptables for some configurations, there can be a fair amount of software configuration outside of Piranha Configuration Tool. In particular, FTP services and the use of firewall marks requires extra manual configuration of the LVS routers to route requests properly.

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