When configuring the router with the NAT TCP load balancing where the inside cloud includes several server used as a pool of server (using rotary option), I can imagine that one or several server can fail.
- does the router do the allocation of inside local address only among the server which are not failed ?
- how does the server know if a server is failed or not ? By performing a ping or does it monitor if a TCP connection is successful or not ?
Thats the problem with NAT TCP load balancing. Router will still try to send the Nth connection (on round robin basis) to a particular server and if that server fails, it will still send the connection to taht server and connection will fail.
Cisco Local Director helps in preventing this problem. It keeps track of which servers are active and which are not, using a keepalive mechanism and hence connections wont fail.
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