Droms R. The DHCP handbook

15 Frame Relay.

16 ATM.

17 HDLC.

18 Fibre Channel.

19 ATM.

20 Serial Line.

21 ATM.

22 MIL-STD-188-220.

23 Metricom.

24 IEEE 1394.1995.

25 MAPOS.

26 Twinaxial.

27 EUI-64.

28 HIPARP.

29 IP and ARP over ISO 7816-3.

30 ARPSec.

31 IPsec tunnel.

32 InfiniBand (TM).

The variable-format Section

Figure C.2 shows the format of each option in the

variable-format

section, and Table

C.3 explains the use of each of the fields identified in Figure C.1. Appendix D,

“DHCP Options Summary,” includes a summary of all the options that can be

included in the

variable-format

section.

APPENDIX C The DHCP Message Format506

TABLE C.2 Continued

htype Value Network Hardware Type

option

code

length option value

. . .

FIGURE C.2 The fields in the variable-format section of a DHCP message.

TABLE C.3 The Fields in the variable-format Section of a DHCP Message

Field Length Description

option code 1 byte Identifies the specific option; see Appendix D for a list of

DHCP options.

length 1 byte Number of bytes in the option value.

option value length bytes Data value for this option.

033 3273 App C 10/3/02 5:03 PM Page 506

DHCP Options Summary

This appendix includes two tables of DHCP options.

Table D.1 lists the options in alphabetical order, and Table

D.2 lists the options in numeric order. Table D.1 includes

the names that the ISC and Microsoft DHCP servers use to

identify DHCP options, along with a short description of

each option. The Microsoft DHCP server does not give

names to all options; the entries for those options are

blank. Unless otherwise indicated, all the DHCP options

are defined in RFC 2132.

034 3273 App D 10/3/02 5:03 PM Page 507

APPENDIX D DHCP Options Summary508

TABLE D.1

DHCP Options, Listed Alphabetically

Option Name

Code ISC Option Name

Microsoft Option Name Description

All subnets are local 27

all-subnets-local

All subnets are local 0

specifies that the client should

assume that some IP subnets have

smaller MTUs;

specifies that all

subnets have same MTU as subnet

to which the client is connected

ARP cache timeout 35

arp-cache-timeout

ARP Cache Timeout

Timeout (in seconds) for ARP

cache entries

Autoconfiguration 116

autoconfiguration

specifies that the client should

not perform link-local IP address

autoconfiguration;

specifies that

the client should perform auto-

configuration

Boot file size

boot-size

Boot File Size

Size of the client bootfile in 512-

byte blocks

Boot file name

bootfile-name

Boot File Name

Name of the bootfile to use when

the File field is used to carry

options

Broadcast address 28

broadcast-address

Broadcast Address

The broadcast address for the

subnet to which the client is

attached

Client identifier

dhcp-client-identifier Client’s unique identifier

Cookie server

cookie-servers

Cookie Servers

Cookie servers

Default IP TTL

default-ip-ttl

Default Time-to-Live

Default TTL client should use for

outgoing datagrams

DHCP Authentication 90

authentication

Option used to authenticate

option

DHCP packets transmitted by

clients and servers

034 3273 App D 10/3/02 5:03 PM Page 508

DHCP Message Type 53

dhcp-message-type

Identifies the type of the DHCP

message; see the section “

DHCP

message type”

in Chapter 9 for

details

Domain Name Servers 6

domain-name-servers DNS Servers

List of DNS server IP addresses

Domain name

domain-name

Domain Name

Default name for DNS name

resolution

End

255

option-end

Indicates end of options in field

Ethernet encapsulation 36

ieee802-3-encapsulation Ethernet encapsulation

specifies Ethernet Version 2

encapsulation

;

specifies IEEE

802.3

Extensions path

extensions-path

Extensions Path

The name of the file containing

additional options to be inter-

preted according to RFC 2132

format

Finger server

finger-server

Finger Servers

List of finger server

IP addresses

Host name

host-name

Host Name

Client hostname

Impress server

impress-servers

Impress Servers

Imagen Impress printer servers

Interface MTU

interface-mtu

MTU Option

Value of MTU that the client

should use for this interface

Length of DHCP lease 51

dhcp-lease-time

Lease duration (expressed in

seconds) for the assigned IP

address

IP forwarding

ip-forwarding

IP Layer Forwarding

specifies that datagram forward-

ing between interfaces is to be

disabled;

specifies that forward-

ing is to be enabled

IRC server

irc-server

Internet Relay Chat (IRC)

List of Internet Relay Chat

server

Servers

IP addresses

APPENDIX D DHCP Options Summary 509

TABLE D.1

Continued

Option Name

Code ISC Option Name

Microsoft Option Name Description

034 3273 App D 10/3/02 5:03 PM Page 509

Log server

log-servers

Log Servers

MIT-LCS log servers

LPR server

lpr-servers

LPR Servers

LPDP (Unix

lpr

)

servers

Mask supplier

mask-supplier

Mask Supplier Option

specifies that the client should

not respond to ICMP subnet mask

request messages;

specifies that

the client should respond

Maximum datagram 22

max-dgram-reassembly Max DG Reassembly Size

Maximum size of datagram that

reassembly the client should

expect to reassemble

Maximum DHCP 57

dhcp-max-message-size

Maximum DHCP message size

message size accepted by the

client

Merit dump file

merit-dump

Merit Dump File

Name of file for memory dump

Message

dhcp-message

Message from the server to be

displayed to the user by the client

Mobile IP home agents 68

mobile-ip-home-agents Mobile IP Home Agents

List of mobile IP home agents

Name server

ien116-name-servers Name Servers

IEN 116 name servers

Name Service

117

name-service-

Ordered list of name service types

Search Order

search-order

that the client should use

NDS context

nds-context

Initial Netware Directory Service

(NDS) for client

NDS server

nds-servers

List of NDS servers

NDS tree name

nds-tree-name

NDS tree name for the client to

use

NetBIOS over TCP/IP 45

netbios-dd-server

NetBIOS over TCP/IP NBDD

List of NetBIOS Datagram data-

gram distribution

Distribution (NBDD) servers

NetBIOS over TCP/IP 44

netbios-name-servers WINS/NBNS Servers

List of NetBIOS Name Server

name server

(NBNS) IP addresses

APPENDIX D DHCP Options Summary510

TABLE D.1

Continued

Option Name

Code ISC Option Name

Microsoft Option Name Description

034 3273 App D 10/3/02 5:03 PM Page 510

NetBIOS over TCP/IP 46

netbios-node-type

WINS/NBT Node type

Client’s NetBIOS over TCP/IP node

type

node type

; see the section

“

NetBIOS address over TCP/IP

node type

” in Chapter 9 for

details

NetBIOS over TCP/IP 47

netbios-scope

NetBIOS Scope ID

Client’s NetBIOS over TCP/IP

scope

NetWare/IP domain 62

nwip-domain

Name of NetWare/IP domain for

client

NetWare/IP information 63

nwip.nsq-broadcast nwip.

NetWare/IP parameters; see the

preferred-dss nwip.

section “NetWare/IP Suboptions “

nearest-nwip-server

in Chapter 9 for details

nwip.autoretries nwip.

autoretry-secs nwip.

nwip-1-1 nwip.

primary-dss

NIS domain Name 40

nis-domain

NIS Domain Name

Client’s Network Information

Service (NIS) domain

NIS servers

nis-servers

NIS Servers

List of NIS servers

NIS+ domain Name 64

nisplus-domain

NIS+ Domain Name

Client’s Network Information

Service+ (NIS+) domain

NIS+ servers

nisplus-servers

NIS+ Servers

List of NIS+ server IP addresses

NNTP server

nntp-server

Network News Transport

List of NNTP servers

Protocol (NNTP) Servers

APPENDIX D DHCP Options Summary 511

TABLE D.1

Continued

Option Name

Code ISC Option Name

Microsoft Option Name Description

034 3273 App D 10/3/02 5:03 PM Page 511

Non-local source routing 20

non-local-source-routing Non-local Source Routing

specifies that forwarding of

datagrams with nonlocal source

routes is to be disallowed;

speci-

fies that forwarding of such data-

grams is to be allowed

NTP servers

ntp-servers

NTP Servers

List of Network Time Protocol

(NTP)

servers

Option overload 52

dhcp-option-overload

Specifies whether File and Sname

fields are used to carry options

Pad

pad

Carries no data

Parameter request list 55

dhcp-parameter-

List of options requested by the

request-list

client

Path MTU aging 24

path-mtu-aging-seconds Path MTU Aging Timeout

Timeout (in seconds) for aging

PMTU values

Path MTU plateau table 25

path-mtu-plateau-table Path MTU Plateau Table

List of MTU sizes for PMTU

discovery

Perform mask discovery 29

perform-mask-discovery Perform Mask Discovery

specifies that the client should

not perform ICMP subnet mask

discovery;

specifies that the

client should perform subnet mask

discovery

Perform router discovery 31

router-discovery

Perform Router Discovery 0

specifies that the client should

not perform router discovery

;

specifies that the client should

perform router discovery

Policy filter

policy-filter

Policy Filter Masks

List of policy filters for nonlocal

source routing

POP3 server

pop-server

Post Office Protocol

List of Post Office Protocol 3

APPENDIX D DHCP Options Summary512

TABLE D.1

Continued

Option Name

Code ISC Option Name

Microsoft Option Name Description

034 3273 App D 10/3/02 5:03 PM Page 512

(POP3)

server IP

(POP3) Servers

addresses

Requested IP address 50

dhcp-requested-address

IP address requested by the client

Relay Agent Information 82

relay-agent-information

Additional information supplied by

the relay Option

agent

Resource location servers 11

resource-location-servers Resource Location Servers

Resource Location Protocol

servers

Root path

root-path

Root Path

Name of the client’s root disk

Router solicitation 32

router-solicitation- Router Solicitation

The address the client should use

for router

address

Address

address discovery

Routers

routers

Router

IP addresses of default routers to

use on the client’s network

segment

Server identifier

dhcp-server-identifier

The IP address of the DHCP server

SLP Directory Agent 78

slp-directory-agent

The Service Location Protocol

Directory agent

SLP Service Scope 79

slp-service-scope

The Service Location Protocol

service scope

SMTP server

smtp-server

Simple Mail Transport

List of Simple Mail Transport

Protocol (SMTP) Servers

Protocol (SMTP) servers

Static route

static-routes

Static Route Option

List of static routes; each static

route includes a destination

StreetTalk directory 76

streettalk-directory- StreetTalk Directory

List of STDA servers

assistance server

assistance-server

Assistance (STDA) servers

StreetTalk server 75

streettalk-server

StreetTalk Servers

List of StreetTalk servers

Subnet mask

subnet-mask

The subnet mask for the network

segment to which the client is

connected

Subnet Selection 118

subnet-selection

The subnet number to use in

APPENDIX D DHCP Options Summary 513

TABLE D.1

Continued

Option Name

Code ISC Option Name

Microsoft Option Name Description

034 3273 App D 10/3/02 5:03 PM Page 513

Option

selecting the client IP address

Swap server

swap-server

Swap Server

The swap server for the client

dhcp-renewal-time

The time, in seconds, until the

client should renew the lease on

the assigned address

dhcp-rebinding-time

The time, in seconds, until the

client should rebind the lease on

the assigned address

TCP default TTL

default-tcp-ttl

Default TTL Option

The default TTL for TCP segments

TCP keepalive garbage 39

tcp-keepalive-garbage Keepalive Garbage

specifies that the client should

not send a garbage byte with a

TCP keepalive message;

specifies

that the client should send a

garbage byte

TCP keepalive interval 38

tcp-keepalive-interval Keepalive Interval

The time, in seconds, to wait

before sending a keepalive

message on a TCP connection

TFTP server name 66

tftp-server-name

Boot Server Host Name

The name of the TFTP server to

use when the Sname field is used

to carry options

Time offset

time-offset

Time Offset

The time offset, in seconds, from

Coordinated Universal Time (UTC)

for the client’s network segment

Time

server

time-servers

Time Server

The time server’s IP addresses

Trailer 34

trailer-encapsulation Trailer Encapsulation

specifies that the client should

APPENDIX D DHCP Options Summary514

TABLE D.1

Continued

Option Name

Code ISC Option Name

Microsoft Option Name Description

034 3273 App D 10/3/02 5:03 PM Page 514

not negotiate the use of trailers

through ARP

;

specifies that the

client should negotiate the use of

trailers

UAP servers

uap-servers

List of URLs specifying User

Authentication Protocol servers

User Class

User class information

Vendor class identifier 60

vendor-class-identifier

Vendor identification

Vendor specific

vendor-encapsulated- Vendor Specific Info

Vendor-specific information; see

information

options

the section “

vendor-specific

information

” in Chapter 9 for a

description of the contents

WWW server

www-server

World Wide Web (WWW)

List of World Wide Web server IP

Servers

addresses

X Window System 49

x-display-managers

X Window System Display

List of X Window System display

Display Managers

managers

X Window System 48

font-servers

X Window System Font

List of X Window System font

font server

servers

RFC 2563

RFC 865

RFC 3118

RFC 894

RFC 1042

RFC 1179

RFC 2937

APPENDIX D DHCP Options Summary 515

TABLE D.1

Continued

Option Name

Code ISC Option Name

Microsoft Option Name Description

RFC 2241

RFC 1001,

RFC 1002

RFC 2242

RFC 1305

RFC 1191

RFC 1256

RFC 3046

RFC 887

RFC 2610

RFC 3011

RFC 868

2812, RFC 2813

RFC 1939

RFC 893

RFC 2485

RFC 3004

RFC 1198

RFC 1288

RFC 2811, RFC

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