Custom TCP/IP Stacks

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vSphere at 5.1 and earlier, there was a single TCP/IP stack which was being used by all the different types of network traffics. This meant that management, virtual machine (VM) traffic, vMotion, NFC etc.. were all fixed to use the same stack. and because of the shared stack, all VMkernel interfaces had some things in common: they have to have the same default gateway, the same memory heap, and the same ARP and routing tables.

from vSphere 5.5 onward , VMware has changed this functionality, allowing for multiple TCP/IP stacks, but with some limitations. Only certain types of traffic could make use of a stack other than the default one, and the custom TCP stack had to be created from the command line using an ESXCLI command. 

In vSphere 6, VMware went ahead and created separate vMotion and Provisioning stacks by default , and when you deploy NSX , this will create its own stack.

NOTE – Custom TCP/IP stacks aren’t supported for use with fault tolerance logging, management traffic, Virtual SAN traffic, vSphere Replication traffic, or vSphere Replication NFC traffic.

Create a Custom TCP/IP Stack:

To create a new TCP/IP stack we must use the ESXCLI…

>esxcli network ip network add -N=”stack name”

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Modify Custom TCP/IP Stack Settings:

Now since you have created your custom stack , it needs to be configured with settings like which DNS settings to use, which address to use as the default gateway etc. in advanced settings you can configure , which congestion control algorithm to use, or the maximum number of connections that can be active at any particular time.

To configure these settings, GO to Manage > Networking > TCP/IP configuration and highlight the your stack to be configured.

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on the edit page , these settings can be modified:

  • Name. Change Name if Required.
  • DNS Configuration.use DHCP, so the custom TCP/IP stack can pickup the settings from DHCP or  static DNS servers with search domains.
  • Default Gateway. One of the primary reasons for creating a separate TCP/IP stack from the default one and this can be configured here.
  • Congestion Control Algorithm. The algorithm specified here affects vSphere’s response when congestion is suspected on the network stack.
  • Max Number of Connections. The default is set to 11,000.

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Configuring custom TCP/IP stacks also will help you have separate gateway for each kind of traffic if that’s the way network has been designed.

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