Work with DHCP option sets

Domain name (optional): Enter the domain name that a client should use when resolving hostnames via the Domain Name System. If you are not using AmazonProvidedDNS, your custom domain name servers must resolve the hostname as appropriate. If you use an Amazon Route 53 private hosted zone, you can use AmazonProvidedDNS. For more information, see DNS attributes for your VPC.

Some Linux operating systems accept multiple domain names separated by spaces. However, Windows and other Linux operating systems treat the value as a single domain, which results in unexpected behavior. If your DHCP option set is associated with a VPC that has instances running operating systems that treat the value as a single domain, specify only one domain name.

Domain name servers (optional): Enter the DNS servers that will be used to resolve the IP address of a host from the host's name.

You can enter either AmazonProvidedDNS or custom domain name servers. Using both might cause unexpected behavior. You can enter the IP addresses of up to four IPv4 domain name servers (or up to three IPv4 domain name servers and AmazonProvidedDNS) and four IPv6 domain name servers separated by commas. Although you can specify up to eight domain name servers, some operating systems might impose lower limits. For more information about AmazonProvidedDNS and the Amazon DNS server, see Amazon DNS server.

NTP servers (optional): Enter the IP addresses of up to eight Network Time Protocol (NTP) servers (four IPv4 addresses and four IPv6 addresses).

NTP servers provide the time to your network. You can specify the Amazon Time Sync Service at IPv4 address 169.254.169.123 or IPv6 address fd00:ec2::123. Instances communicate with the Amazon Time Sync Service by default. Note that the IPv6 address is only accessible on EC2 instances built on the Nitro System.

For more information about the NTP servers option, see RFC 2132. For more information about the Amazon Time Sync Service, see Set the time for your instance in the Amazon EC2 User Guide for Linux Instances.

NetBIOS name servers (optional): Enter the IP addresses of up to four NetBIOS name servers.

For EC2 instances running a Windows OS, the NetBIOS computer name is a friendly name assigned to the instance to identify it on the network. The NetBIOS name server maintains a list of mappings between NetBIOS computer names and network addresses for networks that use NetBIOS as their naming service.

NetBIOS node type (optional): Enter 1, 2, 4, or 8. We recommend that you specify 2 (point-to-point or P-node). Broadcast and multicast are not currently supported. For more information about these node types, see section 8.7 of RFC 2132 and section 10 of RFC1001.

For EC2 instances running a Windows OS, this is the method that the instances use to resolve NetBIOS names to IP addresses. In the default options set, there is no value for NetBIOS node type.

IPv6 Preferred Lease Time (optional): A value (in seconds, minutes, hours, or years) for how frequently a running instance with an IPv6 assigned to it goes through DHCPv6 lease renewal. Acceptable values are between 140 and 2147483647 seconds (approximately 68 years). If no value is entered, the default lease time is 140 seconds. If you use long-term addressing for EC2 instances, you can increase the lease time and avoid frequent lease renewal requests. Lease renewal typically occurs when half of the lease time has elapsed.