When troubleshooting, it can sometimes be difficult to determine if you are dealing with a hardware issue or a configuration issue. In this article, we will go through some basic methods for ruling out a hardware issue with additional IPs or vRack on your Dedicated Server.
Prerequisites
Topics
Testing Additional IPs
Configured as an Alias (without VMAC)
To begin, put your server into rescue mode as described in our How to Use Rescue Mode on a Dedicated Server article. Once you are in rescue mode, use the following command to identify your NIC.
# ip a
To find the correct NIC in your output, find the NIC which has your server's public IP address attached. In this article, we use the example interface eth0. We will add our additional IP to the interface using the following command. Change the parts of the command in red to reflect your machine's parameters.
# ip addr add 203.0.113.1/32 dev eth0
To test that your additional IP is functioning properly, ping it from a separate machine. If you are concerned that you are having routing issues, you can perform an mtr (My traceroute) test. In our example, we use an OpenDNS server. Change the IP address in red to your IP address.
# mtr -rbwz 208.67.222.222 -a 203.0.113.1
If you determine that you have routing issues, send the outputs of the following tests to OVHcloud US Support.
# ip a
# ip r
# mtr -rbwz 208.67.222.222 -a 203.0.113.1
Bridge Configuration (with VMAC)
For a bridge configuration the above steps will work with one modification. To add our additional IP to the interface, we will use the following four commands instead of the ip addr add command used above.
In our example, we name our test link "testrescue." Replace the parameters in red with those on your machine. If you need help finding your Virtual MAC, check out the following article: How to Assign a Virtual MAC to an Additional IP
# ip link add name testrescue link eth0 type macvlan
# ip link set dev testrescue address 00:53:00:00:00:00
# ip link set testrescue up
# ip addr add 203.0.113.1 dev testrescue
Next, we'll take a look at how to perform these same tests with vRack.
Testing vRack
Note: Before testing your vRack connection, make sure both of the servers you use are on the same vRack.
To begin testing that your vRack connection works, put two servers into rescue mode. You can reference our How to Use Rescue Mode on a Dedicated Server article to learn how to do this.
Once you have gained access to rescue mode, we will configure both servers. We will use the same configuration on both servers, but with different private IP addresses. First find your private interface using the following command:
# ip a
Next, we will set our network configuration. To do so, open the interface file using the following command.
# vim /etc/network/interfaces
Below is a sample configuration for this file. Make sure the private IPs you use on both servers are on the same subnet.
# interfaces(5) file used by ifup(8) and ifdown(8) # Include files from /etc/network/interfaces.d: source-directory /etc/network/interfaces.d auto eth1 iface eth1 inet static address 192.168.70.5 netmask 255.255.255.0 gateway 192.168.70.254
Once you have configured both servers, ping one server from the other. If it works, you know you have a working vRack. If it does not, contact OVHcloud US support and send them the configuration files and results of your failed ping test.
Conclusion
Having read this article, you should now know how to perform basic networking tests in rescue mode for your additional IPs and vRack.