Discovered a MAJOR, really irritating bug

Hi there.

Im new to the peplink family and the forums but definitely not new to networking. I am a licensed communications contractor and work on technology and networks for a living.

I have a peplink balance20x at my home that has been working great for a month or so and i really like it. was happy to finally get rid of the POS netgear nighthawk that used to work great.

I have comcast for hardwired internet and AT&T SIM card for cellular backup. couple weeks ago comcast went down for “routine maintenance” in the middle of the night, the router notified me, switched to AT&T and then comcast came back up some time later. Everything worked flawlessly

Fast forward to early this morning 12:21am, comcast went down again for “routine maintenance” according to their website and stated should be back up by 6am

I get up about 7am and discover router still on cellular and im not getting public IP from comcast. rebooted everything over and over to no avail

went round and round with tech support at comcast which was worthless. they werent much help.

finally i decided to look at my modem logs to see if i noticed anything.

low and behold discovered that the “learned” mac address (should be mac of WAN port on router), was that of a wireless client on my network. this was really odd. the router was not passing its WAN mac to the modem. So i disconnected all wireless clients, rebooted, and still no comcast public IP. connected to modem and this time the modem had a “learned” mac address that belonged to the LAN mac of the router. WTH

so i cloned the LAN mac to the WAN mac and was able to get back online.

but this is nuts. MAJOR bug. see screenshots below…

not able to upload photos for some reason…

Well that is proper strange, and you don’t have IP passthrough enabled or anything like that?

As a new account you should be able to post pictures once you get this response.

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no IP passthrough that i know of. but comcast went down couple weeks ago and i didnt have this issue. this wasted most of my day and i had to reschedule appointments with clients. so irritating.

still cant upload photos. get the following error- “Discourse::InvalidAccess”


Support team have pickup your ticket and we will investigate further.

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thank you. this was a huge time waster for me and i hope you can find the issue…


Sorry for the inconvenience caused and we will get back to you as soon as possible.

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@wcnetworks Two suggestions. (1) include the make/model of the modem and the firmware level it is running. (2) for problems like this, try connecting a computer directly to the modem, just to be sure there is nothing broken about Comcast or the modem.
And, when you say reboot, its not clear if you are talking about the router or the modem or both. If both, then the reboot sequence matters too.

Oh, and another person who had problems connecting a new Peplink router (dont recall the model) to an existing modem solved the problem by just cloning the WAN MAC of the previous router. FYI.

Assuming you are in the US, you are at the mercy of Comcast for cable modem firmware updates. I know my cable modem is running old firmware with the known cable haunt bug and there is nothing I can do about it other than block LAN devices from

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  1. firmware version is inconsequential since i cant update it myself
  2. i did connect a computer directly to the modem and initially got an internal address (x.x.100.11) but then got a public address so it wasnt comcast.
  3. i rebooted both. rebooted modem then router.

cloning the mac address wouldn’t have fixed this since the router was passing the wrong MAC address to the modem for public IP DHCP request.

as far as blocking LAN devices from there really is no point in that since those devices on that subnet would not be able to pass through the firewall. also, blocking that subnet means you couldnt log into your modem.

anyways, peplink got back to me already, logged into my router, saw the issue, tried to duplicate it in their lab and were able to. so they have acknowledged the bug and are working to fix it.

in the mean time, everything is working with me cloning the LAN side MAC so the cable modem issues a public address to the WAN port.

I had somewhat similar issue once. ISP Modem get LAN client MAC address. It turn out that, we accidentally enable IPv6 and Peplink forward client MAC addresses to ISP Modem.

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but the router should not be using a client host’s mac address for its own WAN MAC…

I know. That’s why I said somewhat similar problem, not the same problem. Does your Peplink IPv6 is enabled? If yes, my guess is that, for some reason, the first MAC that your ISP modem detect is forwarded MAC and it keep remember that way. Try disable IPv6 on Peplink and reboot ISP modem. If problem persist then my guess is wrong. :smiley:

NO, IPv6 is off… but peplink support has already logged into my router remotely, identified the issue and reproduced it in their lab so they are working on a fix for it.

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I get the feeling that firmware 8.1 was rushed out the door before being fully baked.

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wouldnt surprise me.

however, I’m happy they responded right away and saw the issue.

I’m new to Peplink, coming from a netgear nighthawk that used to work great and has now gone downhill. Netgears firmware these days is atrocious. and they dont respond right away or at all sometimes.

this nighthawk router would randomly reboot, tell certain hosts the wifi password was wrong, etc also it would get hit hard with port scan attacks.

it was time to switch to a more robust and advanced router…so far i really like the peplink balance 20x

Coming from a Netgear router, you have taken a huge step up in class with Peplink.

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