andyg
By:
andyg

ping between droplets is duplicated

June 9, 2016 462 views
Networking Miscellaneous Ubuntu

I have two droplets created, one in SF, the other in SGP, when I ping one from the other, I get duplicate responses. Can anyone tell me what's going on with the network that would cause this and is it a problem? (nb not real IP address)

# ping 188.166.22.1
PING 188.166.22.1 (188.166.22.1) 56(84) bytes of data.
64 bytes from 188.166.22.1: icmp_seq=1 ttl=55 time=168 ms
64 bytes from 188.166.22.1: icmp_seq=1 ttl=119 time=168 ms (DUP!)
64 bytes from 188.166.22.1: icmp_seq=2 ttl=55 time=167 ms
64 bytes from 188.166.22.1: icmp_seq=2 ttl=119 time=168 ms (DUP!)
64 bytes from 188.166.22.1: icmp_seq=3 ttl=55 time=167 ms
64 bytes from 188.166.22.1: icmp_seq=3 ttl=119 time=168 ms (DUP!)

3 comments
  • If you have the traceroute command where you run the ping command, then using that might give you better clues as to what is happening to your packets.

  • Hmm, something is not quite right:

    # traceroute 188.166.22.1
    traceroute to 188.166.22.1 (188.166.22.1), 30 hops max, 60 byte packets
     1  107.170.207.254 (107.170.207.254)  7.129 ms  7.037 ms  7.057 ms
     2  198.199.99.237 (198.199.99.237)  0.434 ms  0.388 ms 198.199.99.233 (198.199.99.233)  0.306 ms
     3  xe-0-0-0-23.r05.plalca01.us.bb.gin.ntt.net (129.250.204.117)  1.460 ms xe-0-4-0-17.r06.plalca01.us.bb.gin.ntt.net (129.250.203.81)  1.192 ms xe-0-0-0-23.r05.plalca01.us.bb.gin.ntt.net (129.250.204.117)  1.552 ms
     4  ae-15.r01.snjsca04.us.bb.gin.ntt.net (129.250.5.33)  172.051 ms  171.959 ms  172.000 ms
     5  ae-1.r22.snjsca04.us.bb.gin.ntt.net (129.250.3.26)  1.866 ms ae-11.r22.snjsca04.us.bb.gin.ntt.net (129.250.3.120)  1.771 ms  1.776 ms
     6  ae-2.r20.sngpsi05.sg.bb.gin.ntt.net (129.250.3.49)  174.967 ms  171.591 ms  182.669 ms
     7  ae-2.r00.sngpsi02.sg.bb.gin.ntt.net (129.250.3.147)  168.603 ms  174.504 ms  180.188 ms
     8  116.51.27.190 (116.51.27.190)  173.686 ms 116.51.30.126 (116.51.30.126)  180.269 ms 116.51.27.190 (116.51.27.190)  170.063 ms
     9  * * *
    10  * * *
    11  * * *
    12  * * *
    13  * * *
    14  * * *
    15  * * *
    16  * * *
    17  * * *
    18  * * *
    19  * * *
    20  * * *
    21  * * *
    22  * * *
    23  * * *
    24  * * *
    25  * * *
    26  * * *
    27  * * *
    28  * * *
    29  * * *
    30  * * *
    

    That looks to me like something is looping. What do you think? Similar situation on the other droplet pinging the other direction.

  • @andyg - hops 1, 2, and 8 are all digitalocean addresses, so those are OK. The final hop of the route not being your target IP is most likely because of the firewall rules at DO. The time through the ntt.net gateway has both sort and long time hops, so that's most likely causing the dup problem. Note the time-to-live value of the dup ping packets are about 2x that of the non-dup packets. You can verify that by using the '-t 60' to the ping command, which should eliminate the dup packets.

1 Answer

@andyg

This could be a network issue just as it could be a localized issue between your connection and the Droplet. In many cases, if you're connecting over Wi-Fi or similar, any delay in response to or from your router could trigger duplicate requests.

If you're on Wi-Fi, have you tried disabling Wi-Fi and connecting from a wired connection? If you still see the same, instead of connecting through the router, connect from the modem directly if possible.

This will at least eliminate two potential issues that I've seen numerous times in the past.

  • Hi. As mentioned in the title, this is a ping between two droplets, not me and my droplet. So this is within the digitalocean networks and has nothing to do with my Wi-Fi or home network.

    Any other ideas?

Have another answer? Share your knowledge.