Configure DHCP Static Bindings on a Segment

You can configure static bindings on both DHCP for IPv4 and DHCP for IPv6 servers.

In a typical network environment, you have VMs that run services, such as FTP, email servers, application servers, and so on. You might not want the IP address of these VMs to change in your network. In this case, you can bind a static IP address to the MAC address of each VM (DHCP client). The static IP address must not overlap with the DHCP IP ranges and the DHCP server IP addresses.

DHCP static bindings are allowed when you are configuring either a Local DHCP server or a Gateway DHCP server on the segment. The UI does not prevent you from configuring DHCP static bindings when the segment is using a DHCP Relay. However, in NSX-T Data Center, static binding with a DHCP Relay is an unsupported configuration.

Prerequisites

The segment on which you want to configure DHCP static bindings must be saved in the network.

Procedure

From your browser, log in with admin privileges to an NSX Manager at https://<nsx-manager-ip-address>.
Select Networking > Segments.
Next to the segment that you want to edit, click , and then click Edit.
Expand the DHCP Static Bindings section, and next to DHCP Static Bindings, click Set.
By default, the IPv4 Static Binding page is displayed. To bind IPv6 addresses, make sure that you first click the IPv6 Static Binding tab, and then proceed to the next step.

Click Add Static Binding.

Specify the DHCP static binding options.

The following table describes the static binding options that are common to DHCP for IPv4 and DHCP for IPv6 servers.

Option	Description
Name	Enter a unique display name to identify each static binding. The name must be limited to 255 characters.
IP Address	Required for IPv4 static binding. Enter a single IPv4 address to bind to the MAC address of the client. Optional for IPv6 static binding. Enter a single Global Unicast IPv6 address to bind to the MAC address of the client. When no IPv6 address is specified for static binding, Stateless Address Autoconfiguration (SLAAC) is used to auto-assign an IPv6 address to the DHCPv6 clients. Also, you can use Stateless DHCP to assign other DHCP configuration options, such as DNS, domain names, and so on, to the DHCPv6 clients. For more information about Stateless DHCP for IPv6, read the RFC 3376 specifications. The following types of IPv6 addresses are not permitted in IPv6 static binding: Link Local Unicast addresses (FE80::/64 ) Multicast IPv6 addresses (FF00::/8) Unspecified address (0:0:0:0:0:0:0:0) Address with all F (F:F:F:F:F:F:F:F) The static IP address must belong to the subnet (if any) that is configured on the segment.
MAC Address	Required. Enter the MAC address of the DHCP client to which you want to bind a static IP address. The following validations apply to MAC address in static bindings: MAC address must be unique in all the static bindings on a segment that uses a Local DHCP server. MAC address must be unique in all the static bindings across all the segments that are connected to the gateway and which use the Gateway DHCP server. For example, consider that you have 10 segments connected to a tier-1 gateway. You use a Gateway DHCP server for four segments (Segment1 to Segment4), and a Local DHCP server for the remaining six segments (Segment5 to Segment10). Assume that you have a total of 20 static bindings across all the four segments (Segment1 to Segment4), which use the Gateway DHCP server. In addition, you have five static bindings in each of the other six segments (Segment5 to Segment10), which use a Local DHCP server. In this example: The MAC address in each of the 20 static bindings must be unique across all the segments (Segment1 to Segment4) that use the Gateway DHCP server. The MAC address in the five static bindings must be unique on each segment (Segment5 to Segment10) that use a Local DHCP server.
Lease Time	Optional. Enter the amount of time in seconds for which the IP address is bound to the DHCP client. When the lease time expires, the IP address becomes invalid and the DHCP server can assign the address to other DHCP clients on the segment. Valid range of values is 60–4294967295. Default is 86400.
Description	Optional. Enter a description for the static binding.
Tags	Optional. Add tags to label static bindings so that you can quickly search or filter bindings, troubleshoot and trace binding-related issues, or do other tasks. For more information about adding tags and use cases for tagging objects, see Tags.

The following table describes the static binding options that are available only in a DHCP for IPv4 server.

DHCP For IPv4 Option	Description
Gateway Address	Enter the default gateway IP address that the DHCP for IPv4 server must provide to the DHCP client.
Host Name	Enter the host name of the DHCP for IPv4 client so that the DHCPv4 server can always bind the client (host) with the same IPv4 address each time. The host name must be limited to 63 characters. The following validations apply to host name in static bindings: Host name must be unique in all the static bindings on a segment that uses a Local DHCP server. Host name must be unique in all the static bindings across all the segments that are connected to the gateway and which use the Gateway DHCP server. For example, consider that you have 10 segments connected to a tier-1 gateway. You use a Gateway DHCP server for four segments (Segment1 to Segment4), and a Local DHCP server for the remaining six segments (Segment5 to Segment10). Assume that you have a total of 20 static bindings across all the four segments (Segment1 to Segment4), which use the Gateway DHCP server. In addition, you have five static bindings in each of the other six segments (Segment5 to Segment10), which use a Local DHCP server. In this example: The host name in each of the 20 static bindings must be unique across all the segments (Segment1 to Segment4) that use the Gateway DHCP server. The host name in the five static bindings must be unique on each segment (Segment5 to Segment10) that use a Local DHCP server.
DHCP Options	Optional. Click Set to configure DHCP for IPv4 Classless Static Routes and other Generic Options.

DHCP For IPv4 Option

Description

Gateway Address

Enter the default gateway IP address that the DHCP for IPv4 server must provide to the DHCP client.

Host Name

Enter the host name of the DHCP for IPv4 client so that the DHCPv4 server can always bind the client (host) with the same IPv4 address each time.

The host name must be limited to 63 characters.

The following validations apply to host name in static bindings:

Host name must be unique in all the static bindings on a segment that uses a Local DHCP server.
Host name must be unique in all the static bindings across all the segments that are connected to the gateway and which use the Gateway DHCP server.

For example, consider that you have 10 segments connected to a tier-1 gateway. You use a Gateway DHCP server for four segments (Segment1 to Segment4), and a Local DHCP server for the remaining six segments (Segment5 to Segment10). Assume that you have a total of 20 static bindings across all the four segments (Segment1 to Segment4), which use the Gateway DHCP server. In addition, you have five static bindings in each of the other six segments (Segment5 to Segment10), which use a Local DHCP server. In this example:

The host name in each of the 20 static bindings must be unique across all the segments (Segment1 to Segment4) that use the Gateway DHCP server.
The host name in the five static bindings must be unique on each segment (Segment5 to Segment10) that use a Local DHCP server.

DHCP Options

Optional. Click Set to configure DHCP for IPv4 Classless Static Routes and other Generic Options.

Some additional notes for DHCPv4 static binding:

IPv4 static bindings automatically inherit the domain name that you configured on the segment.
To specify DNS servers in the static binding configuration, add the Generic Option (Code 6 - DNS Servers).
To synchronize the system time on DHCPv4 clients with DHCPv4 servers, use NTP. DHCP for IPv4 server does not support SNTP.
If DHCP Options are not specified in the static bindings, the DHCP Options from the DHCPv4 server on the segment are automatically inherited in the static bindings. However, if you have explicitly added one or more DHCP Options in the static bindings, these DHCP Options are not autoinherited from the DHCPv4 server on the segment.

The following table describes the static binding options that are available only in a DHCP for IPv6 server.

DHCP For IPv6 Option	Description
DNS Servers	Optional. Enter a maximum of two domain name servers to use for the name resolution. When not specified, no DNS is assigned to the DHCP client.
SNTP Servers	Optional. Enter a maximum of two Simple Network Time Protocol (SNTP) servers. The clients use these SNTP servers to synchronize their system time to that of the standard time servers.
Preferred Time	Optional. Enter the length of time that a valid IP address is preferred. When the preferred time expires, the IP address becomes deprecated. If no value is entered, preferred time is auto-calculated as (lease time * 0.8). Lease time must be > preferred time. Valid range of values is 60–4294967295. Default is 69120.
Domain Names	Optional. Enter the domain name to provide to the DHCPv6 clients. Multiple domain names are supported in an IPv6 static binding. When not specified, no domain name is assigned to the DHCP clients.

Some additional notes for DHCPv6 static binding:

Gateway IP address configuration is unavailable in IPv6 static bindings. IPv6 client learns about its first-hop router from the ICMPv6 router advertisement (RA) message.
NTP is not supported in DHCPv6 static bindings.

Click Save after configuring each static binding.