Planning for failover with an L4 or L7 switch

Failover with an L4 or L7 switch

If you deploy transparent proxying with an L4 or L7 switch, NetCache does not need any active failover mechanism. The switch monitors the appliances that it is aware of. The following table shows the failover behavior of a switch for each protocol that NetCache supports for transparent proxying.

Protocol	Type of failover the switch provides
DNS (port 53) FTP (port 21) HTTP (port 80) MMS (port 1755) RTSP (port 554)	Redirects the requests to other appliances or, if all the appliances fail, to the Internet or an internal origin server.
NNTP (port 119)	Redirects requests to other appliances. The switch does not fail over NNTP requests to the Internet. You can, however, configure the switch to fail over to the news server. Before doing so, make sure that your news server can handle the traffic load. News servers generally cannot handle the volume of news requests that appliances can handle. Therefore, failing over to a news server is often not possible.

Protocol

Type of failover the switch provides

DNS (port 53)

FTP (port 21)

HTTP (port 80)

MMS (port 1755)

RTSP (port 554)

Redirects the requests to other appliances or, if all the appliances fail, to the Internet or an internal origin server.

NNTP (port 119)

Redirects requests to other appliances. The switch does not fail over NNTP requests to the Internet. You can, however, configure the switch to fail over to the news server. Before doing so, make sure that your news server can handle the traffic load. News servers generally cannot handle the volume of news requests that appliances can handle. Therefore, failing over to a news server is often not possible.