Odd constant WAN traffic

  • I noticed that the activity light on my cable modem is constantly flashing, even when my lan isn't connected to my router.  So I looked at the RRD graphs in pfsense and I noticed that there is a constant stream of about 5kbps of data coming inbound on the WAN, nothing outbound that I can tell. And none of it is being forwarded to the lan.
    I gave my parents a pfsense router and after noticing this I decided to check theirs one day and it has the exact same problem.

    I recently re-imaged my cf card with version 1.2.3-RC3 and after a fresh configure it still doing the exact same thing.  When I look at the RRD graphs there is a constant 5k of data going coming inbound on the WAN connection.  I re-imaged my parents and it is the same result.

    I am simply wondering what this data being transmitted is?
    Is it something with pfsense?


  • From what I saw on my own cable connection, most of that traffic is made of broadcast: ARP, DHCP. We share the link with our neighbor and we receive their broadcasts and also the broadcast done by the ISP devices.

    A small part of the traffic is evil: "spam" that want to reach the Windows Message Service which says our computer is infected and you need to click on the link to clean it. Well, that what I saw 2 years ago. And that traffic was coming from China at a rate of 2 to 3 message per minute! :o

    Of course, there is some scan in all that.

    You don't have to worry, the firewall blocks all that. You only have to worry about the ports that are forwarded.

  • Rebel Alliance Developer Netgate

    You can monitor the line with tcpdump or pftop and see what is coming across the wire, but it's probably just normal things as the other poster suggested.

    From what others have said, cable lines tend to be bad in terms of "spammy" packets from others around you and from outside sources. pfSense will also send out pings to your gateway periodically to check the WAN quality, so you will see some of that as well.

  • Hi again, thank you for your quick responses, I ran "tcdump -i rl1" to monitor my wan line and it turns out that Zaafiriel was right.  The constant traffic mostly arp request from my isp charter.  It seems like there routers or something constantly ask everyone if there using this or that ip.  I attached some of the output of the command.
    Is this normal from an isp, its seems like a waste of bandwidth, granted its only using about 5kbps, but still…

    Thanks again,


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