Computer receives ping but doesn't respond

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8 points

Computer receives ping but doesn't respond

I found multiple similar questions but none of them helped me.

I have a home network with 2 machines connected to the wifi router. Ping from A to B fails on timeout. tcpdump shows that machine B does see the incoming requests. Ping from B to A works. Both machines run on Mac OS, firewalls disabled, tried connecting them using my Android phone's hotspot wifi with the same result.

I want to connect my laptop (MacBook) to the stationary PC (mac mini) via remote desktop.

This forum has a limit of 5000 characters, so I had to cut out some stuff.

Router

IP = 192.168.1.1

Macbook

IP = 192.168.1.231

Firewall: off

ping works on: localhost, 127.0.0.1, 192.168.1.1 (router), 192.168.1.231 (itself)

ping timeouts on: 192.168.1.185 (mac mini)

nslookup sams-mac-mini successfully resolves to 192.168.1.185

ifconfig: see SuperUser post

netstat -rn (routing table): see SuperUser post

Mac Mini

IP = 192.168.1.185

Firewall: off

ping works on: localhost, 127.0.0.1, 192.168.1.1 (router), 192.168.1.185 (itself), 192.168.1.231 (MacBook)

nslookup sams-mbp successfully resolves to 192.168.1.231

Note: I do have a VPN installed but it's not connected/used at the moment, so you might see something here related to that.

ifconfig: see SuperUser post

netstat -rn:

Routing tables

Internet:
Destination        Gateway            Flags        Netif Expire
default            192.168.1.1        UGSc           en1
127                127.0.0.1          UCS            lo0
127.0.0.1          127.0.0.1          UH             lo0
169.254            link#7             UCS            en1      !
192.168.1          link#7             UCS            en1      !
192.168.1.1/32     link#7             UCS            en1      !
192.168.1.1        20:1f:31:aa:e5:90  UHLWIir        en1   1196
192.168.1.185/32   link#7             UCS            en1      !
192.168.1.255      ff:ff:ff:ff:ff:ff  UHLWbI         en1      !

... see SuperUser post

Tests

Listen for ping requests on mac mini

Run tcpdump -v host 192.168.1.231 on mac mini
Run ping -c 4 192.168.1.185 on MacBook
Mac mini output: see SuperUser post

MacBook got no responses, all 4 requests timed out but as you can see mac mini got all requests and seems to even respond to ARP but ICMP is left without a response.

Disabling IPv6

This gave me an idea it may be caused by Ipv6 so I ran networksetup -setv6off Wi-Fi on both machines which caused no changes, so I enabled it back.

Setting a manual IP for mac mini

This suggests that if I set the IP of mac mini to something else in the DHCP pool it may do something but it didn't (I tried 192.168.1.230 and 192.168.1.232), so I put auto address back.

Disable other network interfaces

Reverse Path Filter seems extremely close to what I have but it's about Linux and Mac OS treats this differently. I didn't spend much time on this but I thought it's related to the machine being confused with network interfaces, so I disabled all of them except the 192.168.* on the mac mini but it didn't fix the problem.

Try a different router

I tried connecting the MacBook and the Mac Mini to my android phone's wifi hotspot but the situation is the same.

Hopefully, we can find a solution and it will even help somebody else in the future.

Mac mini, macOS 10.15

Posted on Nov 3, 2020 4:16 AM

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Answer 1

Best reply

Old Toad

Level 10

207,511 points

Nov 3, 2020 9:21 AM in response to Samkruglov

FYI: you can add up to 10,000 characters by using the Additional Text button:

Boot into Safe Mode (How to use safe mode on your Mac - Apple Support) by booting with the Shift key held down and check there to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing the following;

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts

• Deletes font caches, kernel cache, and other system cache files

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Answer 2

Old Toad

Level 10

207,511 points

Nov 3, 2020 10:44 AM in response to Samkruglov

Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Add Text button to include the report in your reply. How to use the Add Text Feature When Posting Large Amounts of Text, i.e. an Etrecheck Report

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Then we can examine the report and see if we can determine what might be causing the problem.

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Answer 3

Samkruglov Author

Level 1

8 points

Nov 3, 2020 11:49 PM in response to Old Toad

Found it! The root cause was `/Library/Extensions/cpfw.kext` - an extension added by my VPN software. Once I removed it from that folder, the ping started working again!

The idea got from this answer in another question.

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Answer 4

Nov 3, 2020 9:16 AM in response to Samkruglov

I'm wondering if your real router has Wi-FI AP Isolation Mode set up? Many routers don't even have that as a selectable feature although if your WI-FI has a "guest" mode that would include AP isolation. If you aren't using guest WiFi and your router doesn't have that feature enabled (or a similar sounding feature) then I'm not sure what it could be. FYI, this setting/feature keeps any two Wi-Fi clients from talking to each-other as a security measure. FYI, the android wifi hotspot almost certainly has that built-in so it's not a good test at all. Not sure if your Linux machine is on Wi-Fi or not.

Aside from checking your real router to make sure that's not the case I would attach your Mac mini to ethernet to see if this helps. If that works, then it's definitely your router doing AP isolation. Also FYI, both devices don't need to be on ethernet to test this hypothesis, just one (and obviously your Mac mini has an ethernet port).

You can consider seeing if there's a firmware update for your router available. Also, if you can try a second real router you can test (not the Android hotspot) that would be a good, though I consider the ethernet on the mac mini a sufficient test in general just using your one router.

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Answer 5

Samkruglov Author

Level 1

8 points

Nov 3, 2020 9:26 AM in response to Mrokcratron

Thanks for the idea, will try that out! I already tried connecting mac mini via ethernet cable and nothing changed. The router is rented from my ISP, not sure if I have access to admin console. Will see

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Answer 6

Old Toad

Level 10

207,511 points

Nov 3, 2020 1:39 PM in response to Samkruglov

I don't see any of the usual suspects. However, SpokesUpdateService has crashed 57 times. It seems to be associated with a Plantronics hub. Do you have such a hub? If so remove it and run for a bit to see if the problem improves.

Also remove all items from the Login Items preference pane and test. Then add then back one at a time testing each time.

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Answer 7

Samkruglov Author

Level 1

8 points

Nov 3, 2020 11:21 PM in response to Old Toad

No, I don't have a platonics hub.

I tested one other theory: I restarted the pc up to the login screen, so I didn't actually log into any user. At that point the ping fro m macbook still times out but if I do the same in boot safe mode, then, on the login screen, the ping works already. I also tried creating a blank user and log into that but it still doesn't work

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Answer 8

Samkruglov Author

Level 1

8 points

Nov 3, 2020 11:04 AM in response to Old Toad

ok, here it is

report

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Answer 9

Samkruglov Author

Level 1

8 points

Nov 3, 2020 10:12 AM in response to Mrokcratron

I logged into the router console at 192.168.1.1 and there is such setting called "AP Isolation" but it's already turned off. I was hoping that'd be it :(

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Answer 10

Samkruglov Author

Level 1

8 points

Nov 3, 2020 10:34 AM in response to Old Toad

It works in safe mode! Thanks, that's a huge breakthrough! Now I know I need to investigate the "startup items" as mentioned in the guide you linked. Will update later which one was it

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Computer receives ping but doesn't respond

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