BROCADE IP PRIMER

Chapter 15: Server Load Balancing (SLB)State of Real ServerThe real server, and the individual real server ports, can be in one of severaldifferent states. For example:The real server's state is declared in the field just to the right of the realserver's name (above example: “State: Active”). It could be in one of the followingstates:• Enabled (ENB). The real server is configured, but the real server hasfailed the ARP check. The ServerIron cannot reach this real server.• Failed (FAL). The real server has failed the Layer 3 ICMP health check.• Testing (TST). The ARP check has succeeded, but the ICMP check hasnot. We've sent an ICMP Echo Request, but we haven't yet received areply.• Suspect (SUS). The ServerIron keeps track of the time that elapses fromwhen the real server receives a packet and when it responds. If this timeincreases to 3 or 4 seconds, the ServerIron will send a ping. If a reply isnot received, another ping is sent, but the real server is put in “Suspect”state. If a reply is received, the real server is put into Active. If the maximumnumber of retried pings (a configurable parameter) fails, the realserver is put into Failed state.• Grace-dn (GDN). A force-shutdown command has been issued, and theServerIron is gracefully disabling the real server.• Active (ACT). Layer 3 health checks (both ARP and ping) have passed.The real server should be available to receive traffic.State of Real Server PortsEach individual real server port may be in a different state. The possibilitiesare:• Enabled (ENB). This means the same as the real server Enabled state.The real server's been configured, but there is no ARP response.• Failed (FAL). The real server port has failed a Layer 4 or Layer 7 healthcheck.• Testing (TST). The ServerIron is trying its Layer 4 or Layer 7 health checkagain. Layer 3 would still have been successful, but it is trying Layer 4 orLayer 7.• Suspect (SUS). As in the real server Suspect state, the ServerIron keepstrack of how long a real server responds between an incoming packet anda reply. If this gap grows to 3 or 4 seconds, the ServerIron will sendanother Layer 4 health check. If a Layer 7 health check is enabled, it willsend that, too. This happens regardless of when the next scheduledhealth check is.• Grace-dn (GDN). The force-shutdown option has been issued, and thereal server's services are in the process of being gracefully disabled.340 Brocade IP Primer