Load Balancing & Fault Tolerance
WAN Link Health Detection
Detection Protocol
:
Two protocols used to perform WAN link detection are avail-
able: ICMP and TCP.
Detection Period in Second
:
The time interval between ICMP or TCP packets sending for
detection. The unit is second. A shorter interval configuration
can detect connection condition earlier, but it consumes more
bandwidth resource.
Number of Hosts Picked out per Detection
:
The number of hosts that is picked out from Ping List or TCP
Connection List for detection. When FortiWAN starts check-
ing the link health, it will send out ICMP and TCP packets to
the IP address of the hosts that has been picked out. Detec-
tion will not be performed if setting the value to zero.
Number of Retries
:
The number of times FortiWAN retries if a detection being
indicated failed. once all the retries in the number of times
fail, FortiWAN claims the WAN connection fails.
In ICMP packet detection, the optional list is:
Ping List:
Lists the data of hosts (Destination IP: IPv4 or IPv6) available to ping detection. Each detection
sends one ping packet to the IP address of a host that has been picked out randomly from the list. The TTL
(Time to Live) of the ping packet is determined by Hops and generally defined as "3". FortiWAN takes the
TTL expired message as a legal response for a ICMP detection, even the detection packet is not delivered
to the destination.
Note that always employ real external IP addresses (hosts in Internet) for the Ping List, gateway and hosts
in near WAN are not appropriate destinations for the detection.
In TCP packet detection, the optional list is:
TCP Connect List:
Lists the data of hosts (Destination IP: IPv4 or IPv6) available to TCP connect
detection. Each detection performs TCP connect test for a host that has been picked out randomly from
the list, and assigns a value to the TCP port.
A WAN link is determined alive if:
l
A single detection succeeds.
l
Value of field "Number of hosts picked per detection" is sat to zero or "Ping List / TCP Connect List" is leaved blank.
l
"Ignore Inbound Traffic" is disable and inbound traffic on the WAN link is detected.
A WAN link is determined down if:
l
All the detection retries fail.
l
No carrier signal detected (failures on cables or physical ports).
l
The WAN link is disable or a sleeping backup line.
l
A PPPoE or DHCP WAN link which fails to get a dynamic IP address.
FortiWAN provides statistics to the WAN Link Health Detection service, see "
Statistics: WAN Link Health Detection
".
170
FortiWAN Handbook
Fortinet Technologies Inc.
