Home > Uncategorized > Sourcing a ping from a specific interface and address on a Fortigate

Sourcing a ping from a specific interface and address on a Fortigate

The Fortigate ping function doesn’t allow you to specify a source interface, which is sort of annoying.

So instead, you have to source it from a specific address and hope that the Fortigate figures out which interface that address has. I guess this is sort of okay, but it just doesn’t give you as much control as your might want.

execute ping-options view
Ping Options:
        Repeat Count: 5
        Data Size: 56
        Timeout: 2
        Interval: 1
        TTL: 64
        TOS: 0
        DF bit: unset
        Source Address: auto
        Pattern:
        Pattern Size in Bytes: 0
        Validate Reply: no

Sending a ping out of the IP of an interface, where 72.84.109.43 is the interface bound address:

execute ping-options source 72.84.109.43
exec ping 4.2.2.2

The Fortigate will drop all packets sourced by any address other than ICMP from the address set to be the monitor address in the ECMP routing or other ICMP monitors (such as a part of a Load Balancer test).

But, you can monitor return packets easily:

diag debug enable
diag debug console timestamp enable
diag sniffer packet wan2 'host 72.84.109.43' 1

Where ‘wan2’ is the wan interface we want to send traffic out of, where 72.84.109.43 (our ‘exec ping-options source’ address) is bound.

When finished:

diag debug dis
diag debug reset
#ping-options will reset to default when your tty session ends
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