VERDE VDI Network Terms - Networking with Dual-NICs

VERDE VDI Network Terms - Networking with Dual-NICs

Product Line:  VERDE

Preface:      The information contained within this document refers to the networking aspects of the VERDE VDI software solution being installed via a set of RPMs (program modules) on top of CentOS7.  The following networking information is made up of basic CentOS7 (Linux networking) and additions/extensions added from the VERDE VDI installation.


[ Networking with Dual-NICs ]

 It is important to note that in order to configure a VERDE Server with two or more network interface cards (NICs), they must all be assigned to different IP Subnets and NOT part of the same Subnet.  If they were assigned to the same Subnet, this would cause network communications problems.  The reason for that, only one of the Network interfaces on the same Subnet can have a Default Gateway defined.  The other NIC(s) cannot be configured with a Default Gateway.  If one is added, it is ignored by the CentOS network. Thus, if one of the NICs is configured without a Default Gateway, when it receives IP traffic from outside its common Subnet, it would NOT know how to return the packets back to the Source Subnet where the IP traffic originated.  The only Network interface that would be successful is the NIC that has a Default Gateway configured, because it would 'forward’ the IP traffic to the Default Gateway, for proper return routing of the packets.


As we already know, in a Dual-NIC configuration, each Network interface must exist on its own IP Subnet, with its own Default Gateway assigned.


The primary reason for implementing Dual-NICs is to configure each NIC with Static IP addresses for two different Subnets. 

Ex:   NIC1:   192.168.1.50     NIC2:   192.168.2.50

 

Configuring Dual-NICs in this way has the potential to increase bandwidth (up to doubling) of the VERDE Server between the two Subnets.  If the number of endpoints is about equal on both Subnets, the Load-Balancing would be symmetrical, otherwise, asymmetrical, with one NIC having more traffic than the other.


VERDE VDI server is configured with a single PRIMARY IP address of only one of the network interfaces.  This is done during the initial VERDE configuration.  This means that VERDE does NOT 'listen' for connections coming from endpoints on another IP Subnet, such as, in a Dual-NIC configuration.  This scenario would require a more advanced network configuration.

Configuring Dual-NICs on a VERDE VDI server requires some advanced network configuration outside of the VERDE VDI solution.  This is done via the CentOS command line.  By default, VERDE VDI only listens to IP traffic on the network interface of its Primary IP address and does not see traffic from other network interfaces that are configured on different Subnets.  Once a Secondary network interface is connected to a separate Subnet and it has been assigned with its own IP address using the CentOS 7 command line, before any VERDE VDI communications are possible over the new interface, steps are needed to configure Port forwarding, to allow the VERDE server to listen to connections from other network interfaces.



Port Forwarding

This can be performed via the CentOS command prompt, by configuring a specific TCP Port (Port 48622) to be forwarded from a Secondary network interface(s) to the Primary IP address of the VERDE VDI server.  This special configuration requires the use of a CentOS 7 utility called:   socat

 

Here is the CentOS command to install 'socat' from the CentOS 7 command prompt:

]#   yum install socat

 

If prompted, enter 'Y' to allow the install.

Examples of the command to Forward the needed TCP Port

 

1)    socat tcp-listen:TCP-Port,fork,reuseaddr,bind=IP of secondary NIC tcp:Primary IP of Verde server:TCP-Port

         

        Assume Verde Primary IP address is:   192.168.1.55

        Assume the Secondary NIC (on another Subnet) IP address is:   192.168.2.55

        TCP Port that needs to be Forwarded is:   48622

         

        Here is the exact command I use to Forward TCP Port:  48622

        socat tcp-listen:48622,fork,reuseaddr,bind=192.168.2.55 tcp:192.168.1.55:48622 &

 

NOTE:  The special character ‘&’ is needed to send the CentOS command and return control back to the command line.  This interactive command is temporary. The port forwarding configuration is lost upon VERDE server restart.


Start Port Forwarding Automatically

The following CentOS network configuration file and CentOS commands can be used to create a service that will automatically start the Port forwarding at each VERDE server ‘restart’.

 

Creating of the configuration file

Create a file called:   socat0.service

Location of file: /etc/systemd/system/socat0.service

 

Contents of the file begins AFTER this line

[Unit]

Description=socat0

Wants=network.target

After=network.target

 

[Service]

ExecStart=/usr/bin/socat tcp-listen:48622,fork,reuseaddr,bind=192.168.3.55 tcp:192.168.1.56:48622

Restart=always

[Install]

WantedBy=multi-user.target

Once you save the (above) file, run the following commands to initiate the service

 

Creating of the configuration file

$ sudo systemctl daemon-reload

$ sudo systemctl enable socat0.service

$ sudo systemctl start socat0.service

 

NOTE:  If you want to stop the service

$ sudo systemctl stop socat0.service

 

If you want to permanently disable this service (so that it will not start automatically during boot)

$ sudo systemctl disable socat0.service

 

Once the above configuration is in-place, it is necessary to ‘reboot’ the VERDE server.  After the VERDE server restarts, endpoints from each of the two separate Subnets can point their VERDE Client software to the IP address assigned to their network interface of the VERDE server and should be prompted to Login.



Recommended Use Cases for Dual-NICs

Adding a Secondary network interface to the VERDE server allows connectivity from a completely separate IP Subnet within the Organization, without the need to perform advanced network configurations to implement Bonding or Teaming.  Dual-NICs can increase network throughput by doubling the network bandwidth. 

 

This is an ideal solution for smaller Companies that over time, expanded large enough to outgrow their initial network, in terms of available IP addresses.  By adding a Secondary network interface, a new Subnet can be implemented providing another whole TCP address space.




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