In a scenario multipath scenario as below, customer had a requirement to monitor non-active redundant paths via ICMP.
[edit]
user@router# run show route 8.8.8.8
inet.0: 5 destinations, 5 routes (5 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
0.0.0.0/0 *[Static/5] 47w2d 22:13:22
> to 10.20.98.1 via fxp0.0
prod.inet.0: 967373 destinations, 3769559 routes (967373 active, 7045 holddown, 0 hidden)
@ = Routing Use Only, # = Forwarding Use Only
8.8.8.0/24 @[BGP/170] 00:08:17, MED 0, localpref 100
AS path: 3356 15169 I, validation-state: unverified
> to 1.1.1.1 via et-0/0/0.0
[BGP/170] 47w2d 19:23:03, localpref 100
AS path: 6461 15169 I, validation-state: unverified
> to 2.2.2.2 via et-0/0/3.0
[BGP/170] 4w0d 04:00:23, MED 1010, localpref 100
AS path: 174 1273 15169 I, validation-state: unverified
> to 3.3.3.3 via et-0/0/2.0
#[Multipath/255] 00:08:17, metric 0
> to 62.67.19.193 via et-0/0/0.0
to 4.4.4.4 via et-0/0/3.0
However, it was found that with '>ping 8.8.8.8 source <IP of non-active interface> interface <Intrf name> bypass-routing' causes asymetric pattten in which echo-requests to go through the preffered / active path and echo-replies hit the non-active path. This defeats the purpose of monitoring non-active paths.
In order to force both requests and replies through non-active path, please use below CLI:
>ping 8.8.8.8 source <IP of non-active interface> interface <Intrf name> mac-address <MAC addr of non-active interface> bypass-routing