HP 6120XG HP ProCurve Series 6120 Blade Switches Multicast and Routing Guide - Page 103

IP Routing Features

Configuring DHCP Relay

With validation enabled, the relay agent applies stricter rules to variations in

the Option 82 field(s) of incoming server responses to determine whether to

forward the response to a downstream device or to drop the response due to

invalid (or missing) Option 82 information. Table 3-5, below, describes relay

agent management of DHCP server responses with optional validation

enabled and disabled

Table 3-5.

Relay Agent Management of DHCP Server Response Packets.

Response Packet Content

Option 82

Configuration

Validation Enabled on the

Relay Agent

Validation Disabled

(The Default)

Valid DHCP server response

packet without an Option 82

field.

append

,

replace

,

or

drop

1

Drop the server response

packet.

Forward server response

packet to a downstream device.

keep

2





The server response packet

carries data indicating a given

routing switch is the primary relay

agent for the original client

request, but the associated

Option 82 field in the response

contains a

Remote ID

and

Circuit

ID

combination that did not

originate with the given relay

agent.

append


packet.



replace

or

drop

1


packet.


packet.

keep

2





The server response packet

carries data indicating a given

routing switch is the primary relay

agent for the original client

request, but the associated

Option 82 field in the response

contains a

Remote ID

that did not

originate with the relay agent.

append


packet.



replace

or

drop

1


packet.


packet.

keep

2





All other server response

packets

3

append

,

keep

2

,

replace

, or

drop

1





1

Drop is the recommended choice because it protects against an unauthorized client inserting its own Option 82 field for ±

an incoming request.±

2

A routing switch with DHCP Option 82 enabled with the

keep

option forwards all DHCP server response packets except ±

those that are not valid for either Option 82 DHCP operation (compliant with RFC 3046) or DHCP operation without Option ±

82 support (compliant with RFC 2131).±

3

A routing switch with DHCP Option 82 enabled drops an inbound server response packet if the packet does not have ±

any device identified as the primary relay agent (

giaddr

= null; refer to RFC 2131).±

Multinetted VLANs

On a multinetted VLAN, each interface can form an Option 82 policy boundary

within that VLAN if the routing switch is configured to use IP for the remote

ID suboption. That is, if the routing switch is configured with IP as the remote

3-57

Section	Page
HP ProCurve 6120G/XG Switch 6120XG Switch Multicast and Routing Guide	1
Front Cover	1
Title Page	3
Copyright, Notices, & Publication Data	4
Contents	5
Feature Index	12
1. Getting Started	17
Contents	17
Introduction	18
Conventions	18
Command Syntax Statements	18
Command Prompts	19
Screen Simulations	19
Configuration and Operation Examples	19
Keys	19
Sources for More Information	20
Getting Documentation From the Web	22
Online Help	22
Menu Interface	22
Command Line Interface	23
Web Browser Interface	23
Need Only a Quick Start?	24
IP Addressing	24
To Set Up and Install the Switch in Your Network	25
Physical Installation	25
2. Multimedia Traffic Control with IP Multicast (IGMP)	27
Contents	27
Overview	28
IGMP General Operation and Features	29
IGMP Terms	30
IGMP Operating Features	31
Basic Operation	31
Enhancements	31
Number of IP Multicast Addresses Allowed	32
CLI: Configuring and Displaying IGMP	33
How IGMP Operates	38
Operation With or Without IP Addressing	39
Automatic Fast-Leave IGMP	40
Forced Fast-Leave IGMP	42
Configuring Delayed Group Flush	43
Using the Switch as Querier	44
Excluding Well-Known or Reserved Multicast Addresses from IP Multicast Filtering	45
3. IP Routing Features	47
Contents	47
Overview of IP Routing	50
IP Interfaces	51
IP Tables and Caches	51
ARP Cache Table	52
IP Route Table	52
IP Forwarding Cache	53
IP Route Exchange Protocols	54
IP Global Parameters for Routing Switches	54
ARP Age Timer	55
IP Interface Parameters for Routing Switches	58
Configuring IP Parameters for Routing Switches	59
Configuring IP Addresses	59
Changing the Router ID	59
Configuring ARP Parameters	60
How ARP Works	60
Configuring Forwarding Parameters	62
Changing the TTL Threshold	62
Enabling Forwarding of Directed Broadcasts	62
Configuring ICMP	64
Disabling ICMP Messages	64
Disabling Replies to Broadcast Ping Requests	64
Disabling ICMP Destination Unreachable Messages	65
Disabling ICMP Redirects	66
Configuring Static IP Routes	66
Static Route Types	66
Other Sources of Routes in the Routing Table	67
Static IP Route Parameters	67
Static Route States Follow VLAN States	68
Configuring a Static IP Route	68
Configuring the Default Route	70
Configuring RIP	71
Overview of RIP	71
RIP Parameters and Defaults	72
RIP Global Parameters	72
RIP Interface Parameters	72
Configuring RIP Parameters	73
Enabling RIP	73
Enabling IP RIP on a VLAN	74
Changing the RIP Type on a VLAN Interface	74
Changing the Cost of Routes Learned on a VLAN Interface	74
Configuring RIP Redistribution	75
Define RIP Redistribution Filters	75
Modify Default Metric for Redistribution	76
Enable RIP Route Redistribution	76
Changing the Route Loop Prevention Method	77
Displaying RIP Information	77
Displaying General RIP Information	78
Displaying RIP Interface Information	80
Displaying RIP Peer Information	81
Displaying RIP Redistribution Information	83
Displaying RIP Redistribution Filter (restrict) Information	83
Configuring IRDP	84
Enabling IRDP Globally	85
Enabling IRDP on an Individual VLAN Interface	85
Displaying IRDP Information	87
Configuring DHCP Relay	87
Overview	87
DHCP Packet Forwarding	88
Unicast Forwarding	88
Broadcast Forwarding	88
Prerequisites for DHCP Relay Operation	88
Enabling DHCP Relay	89
Configuring a BOOTP/DHCP Relay Gateway	89
Displaying the BOOTP Gateway	90
Operating Notes	91
Configuring an IP Helper Address	91
Operating Notes	91
Verifying the DHCP Relay Configuration	91
Displaying the DHCP Relay Setting	91
Displaying DHCP Helper Addresses	92
DHCP Option 12	93
SNMP Support	93
DHCP Option 82	94
Option 82 Server Support	95
Terminology	96
General DHCP Option 82 Requirements and Operation	97
Option 82 Field Content	98
Forwarding Policies	100
Configuration Options for Managing DHCP Client Request Packets	100
Multiple Option 82 Relay Agents in a Client Request Path	101
Validation of Server Response Packets	102
Multinetted VLANs	103
Configuring Option 82	104
Example of Option 82 Configuration	106
Operating Notes	108
UDP Broadcast Forwarding	110
Overview	110
Subnet Masking for UDP Forwarding Addresses	111
Configuring and Enabling UDP Broadcast Forwarding	112
Globally Enabling UDP Broadcast Forwarding	112
Configuring UDP Broadcast Forwarding on Individual VLANs	112
Displaying the Current IP Forward-Protocol Configuration	114
Operating Notes for UDP Broadcast Forwarding	115
Messages Related to UDP Broadcast Forwarding	115
Index	117
A	117
B	117
C	117
D	117
E	118
F	118
G	118
H	118
I	118
L	119
M	119
O	119
P	119
Q	119
R	119
S	120
T	120
U	120
V	120
W	120

HP 6120XG HP ProCurve Series 6120 Blade Switches Multicast and Routing Guide - Page 103

Multinetted VLANs, Relay Agent Management of DHCP Server Response Packets.

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