Troubleshooting network connection issues caused by Windows network routing

Products

VMware vSphere ESXi

Issue/Introduction

Symptoms:
Windows network routing misconfiguration may cause these issues:

Virtual machine fails to connect to network
Virtual machine network outage
Unable to ping default gateway from virtual machine command line

Environment

VMware ESXi 4.1.x Installable
VMware ESXi 3.5.x Embedded
VMware ESX 4.0.x
VMware ESXi 4.0.x Embedded
VMware ESXi 4.1.x Embedded
VMware ESX Server 3.5.x
VMware ESXi 4.0.x Installable
VMware ESX Server 3.0.x
VMware ESX 4.1.x
VMware ESXi 3.5.x Installable
VMware vSphere ESXi 5.0

Resolution

Note: Being unable to ping default gateway from virtual machine command line may be due to a Windows IPSec issue. Seeing Event ID 4292 and/or 7023 in the Event Viewer of the virtual machine would indicate a possible IPSec issue. If those events are discovered, Right-click on the event and select Properties. There may be a User Action suggested, and in that case, follow the directions provided. For further/related information, see Microsoft KB article 912023.

Route Table

There are some scenarios with multiple NICs connecting to different subnets, where routing statements are required to ensure packets are going out to proper virtual machine networks.

Any virtual machine using TCP/IP as a network protocol has a route table. To route a network packet from one virtual machine using TCP/IP to another, the route is determined by the route table of the virtual machine that is sending the network packet.

A virtual machine's routing table is automatically rebuilt at virtual machine restart. Adding persistent entries to a virtual machine's route table is another a way of establishing routing entries in the route table. Persistent entries are automatically reinserted in a route table each time a computer's route table is rebuilt.

To view the route table, run the command:

>route print

The output looks similar to:

IPv4 Route Table

===========================================================================

Interface List

0x1 ........................... MS TCP Loopback interface

0x10003 ...00 0c 29 9d dd 24 ...... Intel(R) PRO/1000 MT

Network Connection

0x10004 ...00 0c 29 9d dd 2e ...... Intel(R) PRO/1000 MT

Network Connection #2

===========================================================================

Active Routes:

Network Destination Netmask Gateway Interface Metric

0.0.0.0 0.0.0.0 10.10.10.1 10.10.10.30 10

0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.10 10

10.10.10.0 255.255.255.0 10.10.10.30 10.10.10.30 10

10.10.10.30 255.255.255.255 127.0.0.1 127.0.0.1 10

10.255.255.255 255.255.255.255 10.10.10.30 10.10.10.30 10

127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1

192.0.0.0 255.255.255.0 192.168.1.1 192.168.1.10 1

192.168.1.0 255.255.255.0 192.168.1.10 192.168.1.10 10

192.168.1.10 255.255.255.255 127.0.0.1 127.0.0.1 10

192.168.1.255 255.255.255.255 192.168.1.10 192.168.1.10 10

224.0.0.0 240.0.0.0 10.10.10.30 10.10.10.30 10

224.0.0.0 240.0.0.0 192.168.1.10 192.168.1.10 10

255.255.255.255 255.255.255.255 10.10.10.30 10.10.10.30 1

255.255.255.255 255.255.255.255 192.168.1.10 192.168.1.10 1

Default Gateway:

10.10.10.1

===========================================================================

Persistent Routes:

None

From the above output, verify a route statement for each subnet configured on the virtual machine. Confirm that each subnet has its own gateway IP address.

Note: In the output example, there are no persistent route table entries.

Analyzing routing problems

Use the output of the route print command to analyze routing problems.

To use the output to analyze routing problems:

Verify the proper subnet and default gateway.
Check if any persistent route table entries route between subnets.
Verify if any additional subnets have been added to virtual machine. If so, ensure that they are using the proper gateway.

Correcting TCP/IP settings and routing

Go to Start > Settings > Network Connection > LAN or High Speed Internet.
Right-click Local Area Connection and choose Properties.
Choose TCP/IP and click Properties.
Verify the default gateway IP address.
Click Advanced.
If appropriate, modify additional IP addresses/default gateways.

Note: The Local Area Connection number depends on how many NICs are attached to the virtual machine.

Note: Connecting the virtual machine to more than one network interface generates more complex network settings for the network administrator. Keeping networks secure and preventing TCP/IP traffic from looping may require more configuration.

Additional Information

For more information about service console routing, see: