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ICMP / Ping Response not possible to Router LAN IP at the same time as external Internet address.

3: Seeker
3: Seeker

Hey Team


I've been using VF for years with FTTC and had no issues.  I've recently switched to FTTP 900/100 and decided to migrate away from my own PFSense + Unifi Wifi5 setup, in favour of the VF Vox / THG3000, mainly because of Pro 4G backup and the Super boosters, which, 2 + the router seems to give better coverage that my 2 Unifi APs.


Colleagues are reporting that my Zoom video and audio "blips" when I am in calls with them, causing a short pause indicating a disruption to my transmitted data upstream.  I'm assuming downstream is fine, as I don't experience any such issues with their incoming video or audio that I have noticed.  (I'm on Zoom all day long....)


I wanted to ping my Router LAN IP at the same time as (I consider this a well-connected global domain for testing).  When I do this symoultaniously I see an odd behaviour where only one ICMP reply will get back to be from each IP at a time.  As a result, the ping result shows alternating results from the Router LAN OR the external website IP ONLY and not both at the same time: 


It's odd - Any idea why?

Seems to be like a bug in how the router is handling ICMP flow states.

Testing further right now, shows the same issue when pinging two internet IPs!  So it's not isolated to the LAN IP of the router. Can someone with the same router kindly test also?



If I ping exclusively to one or the other it's fine (mostly).

My aim is to spot drops to to figure out if I have a case to raise to VF on the issue causing Zoom to drop, so my pinging the router at the same time, it's a good comparison to tell me if this is my internal network or not.

I am also pinging the mgt IP of the L2 switch which is connected to the VF router directly, and it's solid regardless of the other two tests, so I am highly doubting this is an issue with my internal network.

Generally, this bug seems not very helpful when using multiple ICMP ping tests to monitor network connectivity.

Thanks in advance.



16: Advanced member
16: Advanced member

It would probably be worth setting up a thinkbroadband BQM, as that will give you a record over time of how it is performing.


Thanks a lot, first time I've head of this.  I'll allow ICMP on the WAN and set this up.  Cheers


Any chance you tested the ping issue?

16: Advanced member
16: Advanced member

I've not, but I'm still on FTTC, so my results may not be relevant to you.

Also, I wasn't sure how you were pinging the two addresses simultaneously, so I was waiting for your images to be moderated.


Ah ok fair enough, I see now that the images are not available yet.

I am pinging from my Ethernet connected  MacBook every 200ms.

I’ll keep an eye on the BQM, thanks again for this 👍

16: Advanced member
16: Advanced member

As @Jayach says, we need to see how you are performing the pings.  I'm not using the VF router/modem, and running two CMDs or terminals, pings and MTR/pathping simultaneously does seem to work as expected.


I'm assuming your ping that fails will then work if the other is cancelled?


@Jayach in powershell "ping -t" performs a constant ping...  I'm assuming that's what's being done!

Yes I simply have constant pings running to those two destinations at the same time.

one receives no response and the other does get a response, then they chop and change.  It’s all shown in my screenshots.

as mentioned, It seems to be an issue for the VF router so I’d be very interested if anyone else has the THG3000 and sees the same issue.


16: Advanced member
16: Advanced member

O.K. I am using the THG3000, but I'm on Windows. I have tried to duplicate your test to the same two IP addresses and it all seems fine to me.


Both CMD windows were running at the same time.


Many thanks!


I guess I need to raise a case with VF to see if they can take a pcap in the router.


Appreciate the assistance 👍

So now we have your images, what OS are you using, and by any chance are you using virtualisation?