How to get rid of network broadcasting of port 17500

ajax20 asked:

I get the following in my VPS logs

Aug 11 11:29:22 sv1254 kernel: Firewall: *UDP_IN Blocked* IN=eth0 OUT= MAC=ff:ff:ff:ff:ff:ff:f6:f3:49:7e:0a:54:08:00 SRC=178.162.203.19 DST=255.255.255.255 LEN=131 TOS=0x00 PREC=$ PREC=0x00 TTL=128 ID=6067 PROTO=UDP SPT=17500 DPT=17500 LEN=111

Aug 11 11:29:22 sv1254 kernel: Firewall: *UDP_IN Blocked* IN=eth0 OUT= MAC=ff:ff:ff:ff:ff:ff:f6:f3:49:7e:0a:54:08:00 SRC=178.162.203.19 DST=178.162.203.127 LEN=131 TOS=0x00 PREC=$ PREC=0x00 TTL=128 ID=6068 PROTO=UDP SPT=17500 DPT=17500 LEN=111

Neither the SRC nor the DST are mine. After googling around I found this explanation here and came to know that port 17500 has to do with dropbox’s broadcasting and that I can get rid of it by disabling LANSync in the application or uninstalling it altogether. Still, I’m getting the error in my log file. Any ideas on this would be appreciated.

My answer:


You can’t “get rid of” these so easily. You’re seeing this because other customers of your VPS provider are running Dropbox LAN sync.

Personally I just drop traffic from other nodes in the same subnet without bothering to log it. For example, if your VPS’s IP address is 203.0.113.148 and prefix 24:

-A INPUT -s 203.0.113.0/24 ! -d 203.0.113.148 -m comment --comment "Noisy neighbors" -j DROP

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