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The TCP/IP Guide

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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Network Configuration and Management Protocols (BOOTP, DHCP, SNMP and RMON)
           9  Host Configuration and TCP/IP Host Configuration Protocols (BOOTP and DHCP)
                9  TCP/IP Dynamic Host Configuration Protocol (DHCP)
                     9  DHCP Messaging, Message Types and Formats

Previous Topic/Section
DHCP Options, Option Format and "Option Overloading"
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123
4
56
Next Page
DHCP Client/Server Implementation, Features and Issues
Next Topic/Section

Summary Of DHCP Options / BOOTP Vendor Information Fields
(Page 4 of 6)

Link Layer Parameters Per Interface

Table 195 lists the DHCP/BOOTP options that are specific to a particular link layer (layer two) interface.


Table 195: DHCP/BOOTP Options: Link Layer Parameters Per Interface

Code Value

Data Length (bytes)

Name and Description

34

1

Trailer Encapsulation: When set to 1, tells the client to negotiate the use of trailers, as defined in RFC 893. A value of 0 tells the client not to use this feature.

35

4

ARP Cache Timeout: Specifies how long, in seconds, the client should hold entries in its ARP cache.

36

1

Ethernet Encapsulation: Tells the client what type of encapsulation to use when transmitting over Ethernet at layer two. If the option value is 0, specifies that Ethernet II encapsulation should be used, per RFC 894; when the value is 1, tells the client to use IEEE 802.3 encapsulation, per RFC 1042.


TCP Parameters

The options impacting the operation of TCP are shown in Table 196.


Table 196: DHCP/BOOTP Options: TCP Parameters

Code Value

Data Length (bytes)

Name and Description

37

1

Default TTL: Specifies the default Time To Live the client should use when sending TCP segments.

38

4

TCP Keepalive Interval: Specifies how long (in seconds) the client should wait on an idle TCP connection before sending a “keepalive” message. A value of 0 instructs the client not to send such messages unless specifically instructed to do so by an application.

39

1

TCP Keepalive Garbage: When set to 1, tells a client it should send TCP keepalive messages that include an octet of “garbage” for compatibility with implementations that require this.


Previous Topic/Section
DHCP Options, Option Format and "Option Overloading"
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Pages in Current Topic/Section
123
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56
Next Page
DHCP Client/Server Implementation, Features and Issues
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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