set interfaces virtual-ethernet veth10 peer-name 'veth100'
set interfaces virtual-ethernet veth10 vif 50 address '10.0.50.0/31'
set interfaces virtual-ethernet veth100 peer-name 'veth10'
set interfaces virtual-ethernet veth100 vif 50 address '10.0.50.1/31'

vyos@r14:~$ show interfaces virtual-ethernet 
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface        IP Address                        S/L  Description
---------        ----------                        ---  -----------
veth10           -                                 u/u  
veth10.50        10.0.50.0/31                      u/u  
veth100          -                                 u/u  
veth100.50       10.0.50.1/31                      u/u  
vyos@r14:~$

vyos@r14:~$ ping 10.0.50.1 source-address 10.0.50.0
PING 10.0.50.1 (10.0.50.1) from 10.0.50.0 : 56(84) bytes of data.
64 bytes from 10.0.50.1: icmp_seq=1 ttl=64 time=0.132 ms
64 bytes from 10.0.50.1: icmp_seq=2 ttl=64 time=0.085 ms
64 bytes from 10.0.50.1: icmp_seq=3 ttl=64 time=0.087 ms
^C
--- 10.0.50.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2064ms
rtt min/avg/max/mdev = 0.085/0.101/0.132/0.021 ms
vyos@r14:~$

danhusan@vyos-1:~$ cat /var/run/load-balance/wlb.out
cat: /var/run/load-balance/wlb.out: No such file or directory

vyos@r14# run show reverse-proxy 
Proxy name    Role      Status    Req rate    Resp time    Last change
------------  --------  --------  ----------  -----------  -------------
http          FRONTEND  OPEN      0
https         FRONTEND  OPEN      16
stats         FRONTEND  OPEN      0
bk-01         BACKEND   UP                    1 ms         1h34m45s
default-bk    BACKEND   UP                    0 ms         1h34m45s
bk-01         serv-01   UP                    1 ms         1h34m45s
bk-01         serv-02   DOWN                  0 ms         1h34m44s
default-bk    serv-03   no check              0 ms         1h34m45s
[edit]
vyos@r14#