Recurring Android Wifi DNS problem

[Schlect]

I have an issue with my current Galaxy Note 4 and I had the exact same problem with my previous Galaxy S4. My Wifi works OK most of the time at home and at remote sites. However, when I walk into work, the phone will connect to Wifi, grab an IP address and look like everything is fine. However, as soon as I try to access the internet, I will not be able to. It seems as though there is a DNS problem somewhere. I can access the router web admin page, so TCP is working OK. Rebooting the phone fixes the issue, but I don't want to have to reboot the phone every day I come into work. Other people's phones work fine. I have a Galaxy Tab 4 that works fine too. I have encountered the same problem at some other sites, but most work OK.

What could be the problem here? Incompatible router? DHCP configuration? Why would I be the only one experiencing the issue?

 

[Trees]

Does toggling WiFi off and then back on help? The phone may be trying to figure out which route to take to the internet - mobile data connection or WiFi. If WiFi is on when going from location to location, then it may have "stale" data in its DNS cache, although it sounds like your work's DHCP server also provides gateway and DNS information.

You could try a tool like Terminal Emulator (can run ping at the command line) to see if you can get to a site outside of work's gateway. Try this with mobile data off and WiFi on, and the inverse. May help to isolate where the problem could be. Your IT team may also be able to help to see where the problem may be.

 

[Schlect]

Upon further investigation, it turns out that a device on the wifi network was dishing out DNS info over DHCP. I unplugged everything from the wifi router and lo and behold, the problem went away. What confounds me is, of all the devices connected over wifi, why did only my phone pick up the bad DNS?
To answer your question, yes, sometimes turning wifi on and off fixes it, but mostly not. Rebooting fixed it more reliably. A terminal emulator sounds like a handy app to have on my phone so I will do that today. Thank you.

 

[shiregator]

I think maybe you have the same problem discussed in the following thread (I'm not able to post a link since I have < 10 posts and cannot posts links yet):
525131-why-my-brand-new-s6-so-slow-wi-fi

I've been playing with the manual DNS settings and it does fix the problem, but intermittently. I'm still troubleshooting.

 

[Trees]

I think maybe you have the same problem discussed in the following thread (I'm not able to post a link since I have < 10 posts and cannot posts links yet):
525131-why-my-brand-new-s6-so-slow-wi-fi

I've been playing with the manual DNS settings and it does fix the problem, but intermittently. I'm still troubleshooting.

Good tip. There's some good discussion, troubleshooting, and advice. I added the thread URL here http://forums.androidcentral.com/samsung-galaxy-s6/525131-why-my-brand-new-s6-so-slow-wi-fi.html

 

[Trees]

Upon further investigation, it turns out that a device on the wifi network was dishing out DNS info over DHCP. I unplugged everything from the wifi router and lo and behold, the problem went away. What confounds me is, of all the devices connected over wifi, why did only my phone pick up the bad DNS?
To answer your question, yes, sometimes turning wifi on and off fixes it, but mostly not. Rebooting fixed it more reliably. A terminal emulator sounds like a handy app to have on my phone so I will do that today. Thank you.

Glad you found out the problem source. Sounds like an unauthorized DHCP server is/was on your work's network, and in the DHCP server's scope, the incorrect DNS server was provided. Could also have been a bad gateway address.

It may be that your work has the router environment setup to only accept DHCP requests from devices with a known and approved MAC address, or one that requires authenticating first prior to being granted an IP address (and related DNS, gateway) info that works beyond the router's "quarantine' area for network access requests from unknown devices.

So, if the unauthorized DHCP server was able to grant you an IP address, then it could be that your work does not have MAC filtering in place - unless the unauthorized DHCP server was operating on a different SSID/WiFi network.

Your IT team could probably help verify if the above assumptions I made are valid or not for your work environment.