Can't connect to Azure Linux VM through network

This article fixes an issue in which network errors prevent you from connecting to Azure Linux virtual machines.

Original product version:   Virtual Machine running Linux
Original KB number:   4010059

Symptoms

The primary interface on an Azure Linux virtual machine (VM) is eth0. If eth0 isn't configured, the VM is not accessible over a network connection even when other tools indicate the VM is up.

When the issue occurs, the Secure Shell (SSH) connection that has correct permissions may start to connect to the VM. However, it ultimately cannot access the VM because of the network issue.

The networking errors are typically logged in the serial console log. Specifically, you may see the following errors.

Errors in the serial console log

CentOS Linux distribution errors

Error 1

Bringing up interface eth0:
Device eth0 does not seem to be present, delaying initialization.
[FAILED]

Error 2

Bringing up loopback interface: [ OK ]
Bringing up interface eth0: Device eth0 has different MAC address than expected, ignoring.
[FAILED]

Error 3

YYYY/MM/DD HH:MM:SS Discovered Windows Azure endpoint: ###.##.###.##
/usr/sbin/waagent:2275: DeprecationWarning: BaseException.message has been deprecated as of Python 2.6
Error('socket IOError ' + e.message + ' args: ' + repr(e.args))
YYYY/MM/DD HH:MM:SS ERROR:socket IOError args: (113, 'No route to host')

YYYY/MM/DD HH:MM:SS ERROR:socket IOError args: (113, 'No route to host')
Failed services in runlevel 3:network

Error 4

login: YYYY/MM/DD HH:MM:SS ERROR:timed out

YYYY/MM/DD HH:MM:SS ERROR:Traceback (most recent call last):
YYYY/MM/DD HH:MM:SS ERROR: File "/usr/sbin/waagent", line 3395, in DoDhcpWork
YYYY/MM/DD HH:MM:SS ERROR: receiveBuffer = sock.recv(1024)
YYYY/MM/DD HH:MM:SS ERROR:timeout: timed out
YYYY/MM/DD HH:MM:SS ERROR:
YYYY/MM/DD HH:MM:SS DoDhcpWork: Setting socket.timeout=10, entering recv
YYYY/MM/DD HH:MM:SS ERROR:timed out
YYYY/MM/DD HH:MM:SS ERROR:Traceback (most recent call last):
YYYY/MM/DD HH:MM:SS ERROR: File "/usr/sbin/waagent", line 3395, in DoDhcpWork
YYYY/MM/DD HH:MM:SS ERROR: receiveBuffer = sock.recv(1024)
YYYY/MM/DD HH:MM:SS ERROR:timeout: timed out

Customer changed the IP from DHCP to FIXED

SUSE Linux distribution errors

Setting up (localfs) network interfaces:
 lo 
 lo IP address: 127.0.0.1/8 
 IP address: 127.0.0.2/8 
done eth4 
 No configuration found for eth4
unused Waiting for mandatory devices: eth0 
29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 

eth0 No interface found

Ubuntu

Error 1

cloud-init-nonet waiting 120 seconds for a network device.
cloud-init-nonet gave up waiting for a network device.
ci-info: lo : 1 127.0.0.1 255.0.0.0 .
ci-info: eth1 : 0 . . 00:0d:3a:10:6a:53
route_info failed
Waiting for network configuration...
Waiting up to 60 more seconds for network configuration...
Booting system without full network configuration...

Error 2

ci-info: | eth0 | False | . | . | 00:0d:3a:21:f9:ad |
ci-info: +--------+-------+-----------+-----------+-------------------+
ci-info: !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Route info failed!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+ i=eth0
+ x=0
+ ifdown eth0
ifdown: interface eth0 not configured
+ ifup eth0
Missing required variable: address
Missing required configuration variables for interface eth0/inet.
Failed to bring up eth0.
+ exit 0x\

Resolution

For CentOS

Remove the HWADDR directive from the ifcfg-eth0 file under /etc/sysconfig/network-script.

For SUSE Linux

Remove the files that contain entries for eth0 or eth1 under /etc/udev/rules.d.

For Ubuntu

Error 1

This error indicates that the aneth1 interface is configured instead of eth0. This may occur if the operating system on the VM does not have some updates for udev installed. In this situation, udev incorrectly saves the previous network interface. When the VM is resized or moved, it receives a different MAC address, which will be assigned to eth1.

To resolve this issue, attach the OS disk to another running VM, and then delete the udev rule file under /etc/udev/rules.d/70-persistent-net.rules.

To avoid this issue in the future, we recommend that you update the udev package on the VM. For example, run the following command:

sudo apt-get update
sudo apt-get install udev

Error 2

To resolve this issue, reset the /etc/network/interfaces.d/eth0.cfg file to the default, and make it request the Azure DHCP to obtain an IP address. Then, remove the files in the /var/lib/dhcp folder that contain cached DHCP settings. The following is an example of the default eth0.cfg file:

# The primary network interface
auto eth0
iface eth0 inet dhcp

Resolve the issue on a customized Linux operating system

If the VM that has the networking issue uses your uploaded VHD, you can try to configure the network based on a working gallery image. To do this, attach the problematic disk as a data disk to the gallery VM, and then run the following commands.

fdisk -l
df -h
mount /dev/sdc1 /temporary
df -h
cd /temporary/etc/udev/rules.d
ls -ltr
mv 70-persistent-net.rules /temporary/root/
cd ../../network

ls
mv interfaces interfaces.org
ls -ltr

Copy to the current folder files from the working VM:

cp /etc/network/interfaces . 
cp -R /etc/network/interfaces
cp -R /etc/network/interfaces.d .
cp -R /etc/network/interfaces.dynamic.d .
ls -ltr
cd ..
cd
umount /mnt

For more information about how to attach a data disk to the gallery VM, see How to attach a data disk to a Windows VM in the Azure portal.

Reference: network files for operating systems

Network card configuration

/etc/sysconfig/network-scripts/ifcfg-eth0 ..ifcfg-eth0:1 (Centos, Oracle)
/etc/sysconfig/network/ifcfg-eth0 (SuSE)
/etc/network/interfaces (Ubuntu)  

Hostname configuration

/etc/sysconfig/network (Centos , Oracle)
/etc/HOSTNAME (SuSE)
/etc/hostname (Ubuntu)  

DNS configuration files

/etc/resolv.conf
/etc/nsswitch.conf  

Configuration files for default gateway

set in ifcfg-ethn or /etc/sysconfig/network
/etc/sysconfig/network/route (SuSE)
/etc/network/interfaces (Ubuntu)  

Static routes

/etc/sysconfig/network-scripts/route-ethX (Centos, Oracle)
/etc/sysconfig/network/routes (SuSE)
/etc/network/interfaces (Ubuntu)  

Firewall rules

/etc/sysconfig/iptables (centos, Oracle)
/etc/sysconfig/SuSEfirewall2.d/services (SuSE)
/etc/ufw/ufw.conf (Ubuntu)

Contact us for help

If you have questions or need help, create a support request, or ask Azure community support. You can also submit product feedback to Azure feedback community.