Thursday, December 19, 2019

redhat 7 laptop getting ERR_NETWORK_CHANGED errors in chrome

For a long time, I've been getting and ignoring errors in Chrome on my centos 7 laptop about "ERR_NETWORK_CHANGED".  This often makes transactions in banking and shopping sites fail completely and causes me to switch to a different machine.  Last week I used the Southwest wifi while traveling, and constantly received messages about network disconnects while using google docs.  I'm hoping the problem is the same, but not sure.  It happens with both wired and wireless network connection.

Anyway, I spent some time investigating today.  I thought it was network disconnects, but after looking at lots of generic network troubleshooting info, I searched for the chrome error and found some interesting hits.

This link suggests that the problem is due to ipv6, and disabling it SEEMS to have also solved my problem though it remains to be seen.  But I did not see any details as to WHY ipv6 is a problem, just that it is.  I'm sure if I looked harder I'd find it.  Here is another link about how to disable ipv6, I disabled all 3 properties that it mentions, but I used "sysctl -w" to change the configuration instead of editing sysctl.conf.  The result should be the same.

I used the "watch" command as suggested in the first link to monitor the output of "ip address" and see that the ipv6 interface was occasionally flapping to "tentative".  I used "sysctl -w" to disable ipv6.  And then I used watch again to confirm that the ipv6 interfaces are gone and that the word tentative is no longer appearing in the "ip address" output.

Here are the commands that I found helpful:
watch -n 2 -b -d 'ip address'
sudo sysctl -w net.ipv6.conf.all.disable_ipv6=1
sudo sysctl -w net.ipv6.conf.default.disable_ipv6=1
sudo sysctl -w net.ipv6.conf.lo.disable_ipv6=1
ip address | grep ipv6
watch -d 'ip address | fgrep tentative'
Finally, here is another link for general network troubleshooting that gives some helpful background.

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