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Dell Force10 S25N-S50N FTOS Configuration Guide FTOS 8.4.2.7 E-Series TeraScal - Page 322

Option 82, DHCP Snooping, Circuit ID, Remote ID

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www.dell.com | support.dell.com • DHCP Snooping on page 322 • Dynamic ARP Inspection on page 325 • Source Address Validation on page 327 Option 82 RFC 3046 (Relay Agent Information option, or Option 82) is used for class-based IP address assignment. The code for the Relay Agent Information option is 82, and is comprised of two sub-options, Circuit ID and Remote ID. • Circuit ID is the interface on which the client-originated message is received. • Remote ID identifies the host from which the message is received. The value of this sub-option is the MAC address of the relay agent that adds Option 82. The DHCP relay agent inserts Option 82 before forwarding DHCP packets to the server. The server can use this information to: • track the number of address requests per relay agent; restricting the number of addresses available per relay agent can harden a server against address exhaustion attacks. • associate client MAC addresses with a relay agent to prevent offering an IP address to a client spoofing the same MAC address on a different relay agent. • assign IP addresses according to the relay agent. This prevents generating DHCP offers in response to requests from an unauthorized relay agent. The server echoes the option back to the relay agent in its response, and the relay agent can use the information in the option to forward a reply out the interface on which the request was received rather than flooding it on the entire VLAN. The relay agent strips Option 82 from DHCP responses before forwarding them to the client. Task Insert Option 82 into DHCP packets. For routers between the relay agent and the DHCP server, enter the trust-downstream option. Command Syntax ip dhcp relay information-option [trust-downstream] Command Mode CONFIGURATION DHCP Snooping DHCP Snooping protects networks from spoofing. In the context of DHCP Snooping, all ports are either trusted or untrusted. By default, all ports are untrusted. Trusted ports are ports through which attackers cannot connect. Manually configure ports connected to legitimate servers and relay agents as trusted. 322 | Dynamic Host Configuration Protocol

Section	Page
About this Guide	33
Objectives	33
Audience	33
Conventions	34
Information Symbols	34
Related Documents	34
Configuration Fundamentals	35
Accessing the Command Line	35
CLI Modes	36
Navigating CLI Modes	37
The do Command	40
Undoing Commands	40
Obtaining Help	41
Entering and Editing Commands	41
Command History	42
Filtering show Command Outputs	43
Multiple Users in Configuration mode	44
Getting Started	45
Default Configuration	46
Configure a Host Name	47
Access the System Remotely	47
Access the C-Series and E-Series Remotely	47
Configure the Management Port IP Address	48
Configure a Management Route	48
Configure a Username and Password	48
Access the S-Series Remotely	49
Configure the Enable Password	50
Configuration File Management	50
Copy Files to and from the System	51
Important Points to Remember	51
Save the Running-configuration	52
View Files	53
View Configuration Files	54
File System Management	55
View command history	56
Upgrading and Downgrading FTOS	56
System Management	57
Configure Privilege Levels	57
Create a Custom Privilege Level	57
Removing a command from EXEC mode	58
Move a command from EXEC Privilege mode to EXEC mode	58
Allow Access to CONFIGURATION mode commands	58
Allow Access to INTERFACE, LINE, ROUTE-MAP, and ROUTER mode	58
Apply a Privilege Level to a Username	61
Apply a Privilege Level to a Terminal Line	61
Configure Logging	61
Log Messages in the Logging Buffer	62
Configuration Task List for System Log Management	62
Disable System Logging	62
Send System Messages to a Syslog Server	63
Configure a Unix System as a Syslog Server	63
Change System Logging Settings	63
Display the Logging Buffer and the Logging Configuration	64
Configure a UNIX Logging Facility Level	66
Synchronize Log Messages	67
Enable Timestamp on Syslog Messages	67
File Transfer Services	68
Configuration Task List for File Transfer Services	68
Enable FTP server	68
Configure FTP server parameters	68
Configure FTP client parameters	69
Terminal Lines	69
Deny and Permit Access to a Terminal Line	69
Configure Login Authentication for Terminal Lines	70
Time out of EXEC Privilege Mode	71
Telnet to Another Network Device	72
Lock CONFIGURATION mode	72
Viewing the Configuration Lock Status	73
Recovering from a Forgotten Password	74
Recovering from a Forgotten Enable Password	75
Recovering from a Forgotten Password on S-Series	76
Recovering from a Failed Start	77
802.1ag	79
Ethernet CFM	79
Maintenance Domains	80
Maintenance Points	80
Maintenance End Points	81
Implementation Information	82
Configure CFM	82
Related Configuration Tasks	82
Enable Ethernet CFM	83
Create a Maintenance Domain	83
Create a Maintenance Association	84
Create Maintenance Points	84
Create a Maintenance End Point	84
Create a Maintenance Intermediate Point	85
MP Databases	85
MP Database Persistence	86
Continuity Check Messages	87
Enable CCM	88
Enable Cross-checking	88
Loopback Message and Response	88
Linktrace Message and Response	88
Link Trace Cache	89
Enable CFM SNMP Traps.	90
Display Ethernet CFM Statistics	91
802.3ah	93
Link Layer OAM Overview	93
Link Layer OAMPDUs	94
OAMPDU Flags	94
Link Layer OAM Operational Modes	95
Link Layer OAM Discovery	95
Link Layer OAM Events	96
Remote Loopback	96
Implementation Information	96
Configure Link Layer OAM	97
Related Configuration Tasks	97
Enable Link Layer OAM	97
Adjust the OAMPDU Transmission Parameters	99
Link Performance Event Monitoring	99
Enable Error Monitoring	99
Set Threshold Values	100
Symbol Errors per Second	100
Frame Errors per Second	101
Frame Errors per Frame Period	101
Error Seconds per Time Period	101
Execute an Action upon Exceeding the High Threshold	102
Remote Failure Indication	102
Remote Loopback	103
Display Link Layer OAM Configuration and Statistics	104
Manage Link Layer OAM	106
Enable MIB Retrieval Support/Function	106
Adjust the Size of the Link OAM Event Log	106
802.1X	107
Protocol Overview	107
The Port-authentication Process	109
EAP over RADIUS	110
RADIUS Attributes for 802.1 Support	111
Configuring 802.1X	111
Related Configuration Tasks	111
Important Points to Remember	112
Enabling 802.1X	112
Configuring Request Identity Re-transmissions	114
Configuring a Quiet Period after a Failed Authentication	114
Forcibly Authorizing or Unauthorizing a Port	115
Re-Authenticating a Port	116
Periodic Re-Authentication	116
Configuring Timeouts	117
Dynamic VLAN Assignment with Port Authentication	119
Guest and Authentication-Fail VLANs	121
Configuring a Guest VLAN	121
Configuring an Authentication-Fail VLAN	122
Multi-Host Authentication	123
Multi-Supplicant Authentication	125
MAC Authentication Bypass	127
MAB in Single-host and Multi-Host Mode	128
MAB in Multi-Supplicant Authentication Mode	128
Dynamic CoS with 802.1X	130
IP Access Control Lists (ACL), Prefix Lists, and Route-maps	133
Overview	133
IP Access Control Lists (ACLs)	134
CAM Profiling, CAM Allocation, and CAM Optimization	134
CAM Profiling	135
User Configurable CAM Allocation	135
CAM optimization	136
Test CAM Usage	136
Implementing ACLs on FTOS	137
ACLs and VLANs	137
ACL Optimization	137
Determine the order in which ACLs are used to classify traffic	138
IP Fragment Handling	138
IP fragments ACL examples	139
Layer 4 ACL rules examples	139
Configure a standard IP ACL	140
Configure an extended IP ACL	143
Configure filters with sequence number	143
Configure filters without sequence number	145
Established Flag	146
Configuring Layer 2 and Layer 3 ACLs on an Interface	146
Assign an IP ACL to an Interface	147
Counting ACL Hits	148
Configuring Ingress ACLs	149
Configuring Egress ACLs	149
Egress Layer 3 ACL Lookup for Control-plane IP Traffic	150
Configuring ACLs to Loopback	151
Applying an ACL on Loopback Interfaces	151
IP Prefix Lists	153
Implementation Information	153
Configuration Task List for Prefix Lists	153
Configure a prefix list	154
Use a prefix list for route redistribution	156
ACL Resequencing	157
Resequencing an ACL or Prefix List	158
Route Maps	160
Implementation Information	160
Important Points to Remember	161
Configuration Task List for Route Maps	161
Create a route map	161
Configure route map filters	163
Configure a route map for route redistribution	166
Configure a route map for route tagging	167
Continue clause	167
Bidirectional Forwarding Detection	169
Protocol Overview	169
How BFD Works	170
BFD packet format	170
BFD sessions	173
BFD three-way handshake	173
Session state changes	174
Important Points to Remember	175
Configuring Bidirectional Forwarding Detection	175
Configuring BFD for Physical Ports	176
Related configuration tasks	176
Enabling BFD globally	176
Establishing a session on physical ports	176
Changing physical port session parameters	178
Disabling and re-enabling BFD	179
Configuring BFD for Static Routes	180
Related configuration tasks	180
Establishing sessions for static routes	180
Changing static route session parameters	181
Disabling BFD for static routes	181
Configuring BFD for OSPF	182
Related configuration tasks	182
Establishing sessions with OSPF neighbors	182
Changing OSPF session parameters	184
Disabling BFD for OSPF	184
Configuring BFD for BGP	185
Prerequisites	185
Establishing sessions with BGP neighbors	185
Disabling BFD for BGP	187
Using BFD in a BGP Peer Group	187
Displaying BFD for BGP Information	188
Configuring BFD for IS-IS	193
Related configuration tasks	193
Establishing sessions with IS-IS neighbors	193
Changing IS-IS session parameters	194
Disabling BFD for IS-IS	195
Configuring BFD for VRRP	195
Related configuration tasks	195
Establishing sessions with all VRRP neighbors	195
Establishing VRRP sessions on VRRP neighbors	196
Changing VRRP session parameters	197
Disabling BFD for VRRP	198
Configuring BFD for VLANs	198
Related configuration tasks	199
Establishing sessions with VLAN neighbors	199
Changing session parameters	200
Disabling BFD for VLANs	200
Configuring BFD for Port-Channels	201
Related configuration tasks	201
Establishing sessions on port-channels	201
Changing port-channel session parameters	202
Disabling BFD for port-channels	202
Configuring Protocol Liveness	203
Troubleshooting BFD	203
Border Gateway Protocol IPv4 (BGPv4)	205
Protocol Overview	206
Autonomous Systems (AS)	206
Sessions and Peers	208
Establishing a session	208
Peer Groups	209
Route Reflectors	209
Confederations	210
Communities	210
BGP Attributes	211
Best Path Selection Criteria	211
Best Path selection details	212
Weight	214
Local Preference	214
Multi-Exit Discriminators (MEDs)	214
Origin	215
AS Path	216
Next Hop	217
Multiprotocol BGP	217
Implementing BGP with FTOS	217
Advertise IGP cost as MED for redistributed routes	217
Ignore Router-ID for some best-path calculations	218
4-Byte AS Numbers	218
AS4 Number Representation	219
Dynamic AS Number Notation application	220
AS Number Migration	221
BGP4 Management Information Base (MIB)	223
Important Points to Remember	223
Configuration Information	224
BGP Configuration	225
Defaults	225
Configuration Task List for BGP	225
Enable BGP	226
Configure AS4 Number Representations	230
Configure Peer Groups	232
BGP fast fall-over	235
Configure passive peering	238
Maintain existing AS numbers during an AS migration	239
Allow an AS number to appear in its own AS path	240
Enable graceful restart	241
Filter on an AS-Path attribute	243
Redistribute routes	246
Configure IP community lists	247
Manipulate the COMMUNITY attribute	250
Change MED attribute	251
Change LOCAL_PREFERENCE attribute	252
Change NEXT_HOP attribute	253
Change WEIGHT attribute	253
Enable multipath	254
Filter BGP routes	254
Configure BGP route reflectors	257
Aggregate routes	258
Configure BGP confederations	258
Enable route flap dampening	259
Change BGP timers	263
BGP neighbor soft-reconfiguration	263
Route map continue	265
MBGP Configuration	266
BGP Regular Expression Optimization	267
Retain NH in BGP Advertisement	267
Debugging BGP	267
Storing Last and Bad PDUs	268
Capturing PDUs	269
PDU Counters	271
Sample Configurations	271
Content Addressable Memory	281
Content Addressable Memory	281
CAM Profiles	282
Microcode	284
CAM Profiling for ACLs	285
Boot Behavior	286
When to Use CAM Profiling	287
Important Points to Remember	288
Differences Between EtherScale and TeraScale	288
Select CAM Profiles	288
CAM Allocation	289
Test CAM Usage	290
View CAM Profiles	291
View CAM-ACL settings	291
View CAM Usage	292
Configure IPv4Flow Sub-partitions	293
Configure Ingress Layer 2 ACL Sub-partitions	295
Return to the Default CAM Configuration	297
CAM Optimization	298
Applications for CAM Profiling	298
LAG Hashing	298
LAG Hashing based on Bidirectional Flow	299
CAM profile for the VLAN ACL group feature	299
Troubleshoot CAM Profiling	299
CAM Profile Mismatches	299
QoS CAM Region Limitation	300
Configuration Replace and Rollback	301
Archived Files	301
Configuring Configuration Replace and Rollback	302
Related Configuration Tasks	302
Important Points to Remember	302
Enabling the Archive Service	302
Archiving a Configuration File	303
Viewing the Archive Directory	303
Replacing the Current Running Configuration	303
Rolling Back to the Previous Configuration	304
Configuring an Archive File Maximum	305
Configuring Auto-archive	306
Copying and Deleting an Archive File	307
Viewing and Editing the Contents of an Archive File	307
Viewing the Difference between Configuration Files	308
Dynamic Host Configuration Protocol	311
Protocol Overview	311
DHCP Packet Format and Options	312
Assigning an IP Address using DHCP	313
Implementation Information	314
Configuration Tasks	314
Configure the System to be a DHCP Server	314
Configuration Tasks	315
Related Configuration Tasks	315
Configure the Server for Automatic Address Allocation	315
Create an IP Address Pool	315
Exclude Addresses from the Address Pool	316
Specify an Address Lease Time	316
Specify a Default Gateway	316
Enable DHCP Server	317
Configure a Method of Hostname Resolution	317
Address Resolution using DNS	317
Address Resolution using NetBIOS WINS	318
Allocate Addresses to BOOTP Clients	318
Create Manual Binding Entries	318
Check for Address Conflicts	319
DHCP Clear Commands	320
Configure the System to be a Relay Agent	320
Configure Secure DHCP	321
Option 82	322
DHCP Snooping	322
Enable DCHP snooping	323
Add a static entry in the binding table	324
Clear the binding table	324
Display the contents of the binding table	324
Drop DHCP packets on snooped VLANs only	325
Dynamic ARP Inspection	325
Bypass the ARP Inspection	327
Source Address Validation	327
IP Source Address Validation	328
DHCP MAC Source Address Validation	328
IP+MAC Source Address Validation	328
Equal Cost Multi-Path	331
ECMP for Flow-based Affinity (E-Series)	331
Configurable Hash Algorithm (E-Series)	331
Deterministic ECMP Next Hop	332
Configurable Hash Algorithm Seed	332
Configurable ECMP Hash Algorithm (C- and S-Series)	334
Force10 Resilient Ring Protocol	335
Protocol Overview	335
Ring Status	336
Ring Checking	336
Ring Failure	337
Ring Restoration	337
Multiple FRRP Rings	337
Member VLAN Spanning Two Rings Connected by One Switch	337
Important FRRP Points	338
Important FRRP Concepts	339
Implementing FRRP	340
FRRP Configuration	341
Create the FRRP group	341
Configure the Control VLAN	341
Configure and add the Member VLANs	343
Set FRRP Timers	344
Clear FRRP counters	344
Show FRRP configuration	345
Show FRRP information	345
Troubleshooting FRRP	345
Configuration Checks	345
Sample Configuration and Topology	345
Force10 Service Agent	347
Implementation Information	347
Configure Force10 Service Agent	348
Related Configuration Tasks	348
Enable Force10 Service Agent	348
Specify an SMTP Server for FTSA	349
Provide an Administrator E-mail Address	349
FTSA Messaging Service	350
Enable the FTSA Messaging Service	350
Add Additional Recipients of FTSA E-mails	351
Encrypt FTSA Messages	352
Create a PGP5 encryption key	353
Provide Administrator Contact Information	353
Set the Frequency of FTSA Type 3 Messages	354
Generate FTSA Type 4 Messages	354
Set Parameters FTSA Type 5 Messages	354
FTSA Message Types	355
FTSA Policies	357
Create an FTSA Policy Test List	358
Choose test conditions for a policy test list	358
Set the match criterion for test lists	361
Create a Policy Action List	361
Add actions to a policy action list	362
Create a Policy and Assign a Test and Action List	363
Additional Policy Configurations	364
FTSA Policy Sample Configurations	364
Line card state-change policy configuration	364
Excessive CRC-error policy configuration	369
Debugging FTSA	371
GARP VLAN Registration Protocol	373
Protocol Overview	373
Important Points to Remember	373
Configuring GVRP	374
Related Configuration Tasks	375
Enabling GVRP Globally	375
Enabling GVRP on a Layer 2 Interface	376
Configuring GVRP Registration	376
Configuring a GARP Timer	377
High Availability	379
Component Redundancy	380
RPM Redundancy	380
Boot the chassis with a single RPM	380
Boot the chassis with dual RPMs	381
Automatic and manual RPM failover	382
Communication between RPMs	383
Support for RPM redundancy by FTOS version	384
RPM synchronization	385
RPM redundancy configuration tasks	385
Online Insertion and Removal	387
RPM Online Insertion and Removal	387
Line Card Online Insertion and Removal	387
Pre-configure a line card slot	388
Replace a line card	389
Hitless Behavior	389
Graceful Restart	390
Software Resiliency	390
Runtime System Health Check	391
SFM Channel Monitoring	391
Software Component Health Monitoring	392
System Health Monitoring	392
Failure and Event Logging	392
Trace Log	392
Core Dumps	392
System Log	393
Hot-lock Behavior	393
Warm Upgrade	393
Configure Cache Boot	394
Cache Boot Pre-requisites	394
Select the Cache Boot Image	396
In-Service Modular Hot-Fixes	398
Process Restartability	399
Internet Group Management Protocol	403
IGMP Implementation Information	403
IGMP Protocol Overview	403
IGMP version 2	404
Joining a Multicast Group	404
Leaving a Multicast Group	405
IGMP version 3	405
Joining and Filtering Groups and Sources	406
Leaving and Staying in Groups	407
Configuring IGMP	408
Related Configuration Tasks	408
Viewing IGMP Enabled Interfaces	408

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Match case Limit results 1 per page

322

Dynamic Host Configuration Protocol

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•

DHCP Snooping on page 322

•

Dynamic ARP Inspection on page 325

•

Source Address Validation on page 327

Option 82

RFC 3046 (Relay Agent Information option, or Option 82) is used for class-based IP address assignment.

The code for the Relay Agent Information option is 82, and is comprised of two sub-options, Circuit ID

and Remote ID.

•

Circuit ID

is the interface on which the client-originated message is received.

•

Remote ID

identifies the host from which the message is received. The value of this sub-option is the

MAC address of the relay agent that adds Option 82.

The DHCP relay agent inserts Option 82 before forwarding DHCP packets to the server. The server can

use this information to:

•

track the number of address requests per relay agent; restricting the number of addresses available per

relay agent can harden a server against address exhaustion attacks.

•

associate client MAC addresses with a relay agent to prevent offering an IP address to a client spoofing

the same MAC address on a different relay agent.

•

assign IP addresses according to the relay agent. This prevents generating DHCP offers in response to

requests from an unauthorized relay agent.

The server echoes the option back to the relay agent in its response, and the relay agent can use the

information in the option to forward a reply out the interface on which the request was received rather than

flooding it on the entire VLAN.

The relay agent strips Option 82 from DHCP responses before forwarding them to the client.

DHCP Snooping

DHCP Snooping protects networks from spoofing. In the context of DHCP Snooping, all ports are either

trusted or untrusted. By default, all ports are untrusted. Trusted ports are ports through which attackers

cannot connect. Manually configure ports connected to legitimate servers and relay agents as trusted.

Task

Command Syntax

Command Mode

Insert Option 82 into DHCP packets.

For routers between the relay agent

and the DHCP server, enter the

trust-downstream

option.

ip dhcp relay information-option

[

trust-downstream

]

CONFIGURATION