quoting:
Asymmetric routing in general is a normal, but unwanted situation in an IP network. Asymmetric routing is a situation where for one reason or another packets flowing in i.e. TCP connections flow through different routes to different directions. As a rough example: Host A and B located in different continents are communicating through a TCP connection. Segments sent from host A to host B reach the destination through Sprint link but segments sent from B to A reach the destination through MCI link.
Asymmetric routing as described above is not a problem for current TCP/IP implementations, since TCP connection does not care which route a certain IP packet takes as long as it reaches its destination in a reasonable time.
Asymmetric routing can occur in a smaller scale also. It could happen in a situation where an organization uses two different routes, like a VPN and a leased line, for instance, to their branch office. ...situation where segments on a single connection come in to the network through one node and go out through another node.
Vlad
