I am pinging from directly connected server and this is comparison between ex3400, ex4600 and ex4550.
This wasn't so big issue with "old style" control plane on ex4550:
EX3400:
root@abc:~# ping 10.1.1.63
PING 10.1.1.63 (10.1.1.63) 56(84) bytes of data.
64 bytes from 10.1.1.63: icmp_seq=1 ttl=64 time=2.05 ms
64 bytes from 10.1.1.63: icmp_seq=2 ttl=64 time=8.53 ms
64 bytes from 10.1.1.63: icmp_seq=3 ttl=64 time=295 ms --> nice
64 bytes from 10.1.1.63: icmp_seq=4 ttl=64 time=5.69 ms
64 bytes from 10.1.1.63: icmp_seq=5 ttl=64 time=7.05 ms
64 bytes from 10.1.1.63: icmp_seq=6 ttl=64 time=6.57 ms
64 bytes from 10.1.1.63: icmp_seq=7 ttl=64 time=4.22 ms
Switches is doing nothing. Just factory default config with irb and vlan. SSH session opened on switch
ex4600:
root@abc:~# ping 10.1.1.65
PING 10.1.1.65 (10.1.1.65) 56(84) bytes of data.
64 bytes from 10.1.1.65: icmp_seq=1 ttl=64 time=7.20 ms
64 bytes from 10.1.1.65: icmp_seq=2 ttl=64 time=9.93 ms
64 bytes from 10.1.1.65: icmp_seq=3 ttl=64 time=3.91 ms
64 bytes from 10.1.1.65: icmp_seq=4 ttl=64 time=1.82 ms
64 bytes from 10.1.1.65: icmp_seq=5 ttl=64 time=8.96 ms
64 bytes from 10.1.1.65: icmp_seq=6 ttl=64 time=1.28 ms
ex4550:
root@abc:~# ping 10.1.1.68
PING 10.1.1.68 (10.1.1.68) 56(84) bytes of data.
64 bytes from 10.1.1.68: icmp_seq=1 ttl=64 time=0.770 ms
64 bytes from 10.1.1.68: icmp_seq=2 ttl=64 time=0.793 ms
64 bytes from 10.1.1.68: icmp_seq=3 ttl=64 time=0.809 ms
64 bytes from 10.1.1.68: icmp_seq=4 ttl=64 time=0.703 ms
64 bytes from 10.1.1.68: icmp_seq=5 ttl=64 time=0.767 ms
64 bytes from 10.1.1.68: icmp_seq=6 ttl=64 time=0.742 ms