Utilizing Subnets and IPs

In order to allow our clients to design infrastructures that meet their needs, SoftLayer provides a number of options when it comes to ordering Subnets and IP addresses. Understanding how these work and their intended use cases will help to ensure that you get exactly what you need the first time.

Different Types of Subnets and How Best to Use Them

SoftLayer offers several different types of subnets designed for different use case scenarios. One thing that is common to all of them is you can apply notes to specific IPs in the customer portal in order to allow you to better track what they are being used for. You can edit these notes by following the directions here:


Below you will find descriptions of each type in order to understand them better:

Primary Subnets

Primary Subnets are those that SoftLayer automatically assign on VLANs for automated provisions and services on your VLANs. These subnets are not for you to use for secondary IPs or services as they are used by our automated systems and will be automatically assigned to new servers. If you try to use these on your servers then you may cause an IP conflict and will be required to remove the IP from the server you incorrectly assigned it to.

We are not able to reserve IPs in Primary Subnets for your use.

Portable Subnets

Portable Subnets are the first type of subnet that you can order via the customer portal. They are intended to be used as Virtual Machine addresses or for secondary IPs on servers or secondary interfaces. Another typical purpose of these addresses would be for cluster or HA IPs as they are tracked by our routers via ARP so they can quickly and easily be moved around. The standard format of these subnets will includes its own Network, Gateway, and Broadcast address so three of the IPs will be used right away.

There is a second option for Portable Subnets that can be implemented by opening a support ticket and requesting that the subnet be converted to a “Routed on VLAN” subnet (the standard offering is known as “Secondary on VLAN”). This would then allow you to use all the IPs in the subnet because it would no longer have its own Network, Gateway, or Broadcast IPs. The purpose of this type of subnet it to allow you to have secondary alias IPs on a server that are only used for things such as webserver IPs or for HA. The benefit of this type of subnet is you get more IPs and they can be moved around without manual steps in the customer portal or via a ticket since they are tracked by our routers using ARP.

Static Subnets

Static subnets are the second type of subnet that you can order via the customer portal. They are intended to be used for webservers, email, or other services hosted on a server that needs several additional IPs to allow connections too. Static Subnets are unique in that you have to specify another existing IP that is already assigned to a server that the subnet is directly routed too. This allows you the flexibility to route the subnet as you need and allows you to move it around to different servers, but in order to do that you have to change the routed location in the customer portal.

Global IPs

For information regarding the Global IP Offering, please refer to the Global IP documentation here:


Considerations to Take into Account with Different Subnets:

Hardware Firewalls

Portable Subnets are not protected by firewalls by default. If you need this feature you will need to discuss this with your Sales representative and the subnets that need to be protected can’t be larger than a /29 subnet.

Requesting New Primary IPs on Your Server

In certain circumstances you may need to have certain servers on the same subnet (HA, clustering, etc.). We can accommodate changes to the primary IP on a server, including moving it to a Secondary Subnet if needed. However, you will need to provide adequate justification for the change in a support ticket and these are handled on a case by case basis, and we will not be able to track this for you within our portal.

Transferring Portable IPs Between Servers

When transferring a Portable IP from one server to another you will need to make sure a gratuitous ARP packet is sent out to ensure that our routers update their ARP entry and forward the IP to the correct server. If this is not done then it may take upwards or 4 hours for the IP to start responding correctly.

Vyatta Gateways

When ordering subnets for a VLAN behind a Vyatta Gateway, you will need to ensure the subnet is added correctly to the configuration of the Vyatta and if using VRRP for HA that it is configured correctly to failover between the two gateway devices. If you need further assistance with these please see the following two articles about configuring the Vyatta Gateway: