Ubuntu – 15.04 vivid vervet intermittent selective network outages

15.04ethernetnetworkingupgrade

I recently upgraded from 14.10 to 15.04 and immediately after the upgrade was finished, I began having network problems. At first I thought the errors were related to my squid3 cache, but I have ruled that out as now it is affecting my email as well.

What happens is that sometimes, when I am browsing the web or otherwise using the network (IPv4 only, IPv6 turned off, wired Ethernet connected to a LinkSys WiFi router connected to a cable modem), the system complains that it cannot find DNS info, or cannot connect to, a particular host. This is a very selective outage, because the rest of my connections will be fine in the meantime, and it is only temporary, because if I try again in a couple of minutes, I can successfully connect to the bad host.

I attempted to Google this issue and found no related complaints, so I am wondering if I am unique, or this is something new to 15.04, or I am just going slightly crazy here.

Best Answer

Since upgrading to Ubuntu 15.04 I have experienced similar problems of intermittent internet outages. I believe in my case this is an issue with the routing. The problem for me only happens when I am connected on the internet both through ethernet and through WiFi. The symptom is that I would occasionally lose internet connection for a few seconds. I clearly have a problem with the routing, as my WiFi connection shares priority with my ethernet connection for the addresses related to the DNS server. Check your DNS server address with:

cat /etc/resolv.conf

And your routing table with:

route -n

This issue seems related to a failure of network manager to set priority of ethernet over WiFi since the update to Ubuntu 15.04 and it is being described here:

https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1436330

I have installed network-manager_0.9.10.0-4ubuntu16_amd64.deb libnm-util2_0.9.10.0-4ubuntu16_amd64.deb but I believe the issue is still not thoroughly fixed yet.

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Ubuntu – Mobile broadband sharing over adhoc wireless

Since you're able to use ppp0 and wlan0 both, i'll skip to the main thing. You don't need firestarter. You see to use automatic configuration, you would have to install a DHCP server, which is a fairly painful process, when you take into account all the configuring you need to do. So we'll do this the static way. On your linux machine that is connected to the internet, execute the following commands as root:

iptables -A FORWARD -i ppp0 -o wlan0 -s 192.168.137.1/24 -m conntrack --ctstate NEW -j ACCEPT
iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
iptables -A POSTROUTING -t nat -j MASQUERADE
echo 1 > /proc/sys/net/ipv4/ip_forward

After you do this, go to your other machines and enter the following the the TCP/IPv4 settings for the ad-hoc wireless connection:

IP address: 192.168.137.1-254 (except 100)
Subnet Mask: 255.255.255.0
Gateway: 192.168.137.100

Primary DNS: 8.8.8.8
Secondary DNS: 8.8.4.4

And if everything goes well, you should be able to ping google.com

Ubuntu – 12.04 on VirtualBox -No internet access on Guest OS

For Internet access you can change network option to this :

enter image description here

I had this problem and solve with this option.

Best Answer

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Ubuntu – Mobile broadband sharing over adhoc wireless

Ubuntu – 12.04 on VirtualBox -No internet access on Guest OS

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