Dell PowerEdge FX2 Dell PowerEdge FN I/O Aggregator Configuration Guide 9.6(0 - Page 65
DHCP Packet Format and Options, Option, Number and Description, Subnet Mask, Router, Domain Name
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DHCP Packet Format and Options DHCP uses the user datagram protocol (UDP) as its transport protocol. The server listens on port 67 and transmits to port 68; the client listens on port 68 and transmits to port 67. The configuration parameters are carried as options in the DHCP packet in Type, Length, Value (TLV) format; many options are specified in RFC 2132. To limit the number of parameters that servers must provide, hosts specify the parameters that they require, and the server sends only those parameters. Some common options are shown in the following illustration. Figure 6. DHCP packet Format The following table lists common DHCP options. Option Number and Description Subnet Mask Option 1 Specifies the client's subnet mask. Router Option 3 Specifies the router IP addresses that may serve as the client's default gateway. Domain Name Server Option 6 Specifies the domain name servers (DNSs) that are available to the client. Domain Name Option 15 Specifies the domain name that clients should use when resolving hostnames via DNS. IP Address Lease Time Option 51 Specifies the amount of time that the client is allowed to use an assigned IP address. DHCP Message Type Option 53 • 1: DHCPDISCOVER • 2: DHCPOFFER • 3: DHCPREQUEST • 4: DHCPDECLINE Dynamic Host Configuration Protocol (DHCP) 65