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Dell PowerSwitch S5212F-ON EMC SmartFabric OS10 User Guide Release 10.5.1 - Page 209

Restrictions for DHCP snooping, Rogue DHCP server detection

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When a switch receives DHCP renew, release, or decline messages from a client, it checks the DHCP snooping binding table for a match. If the information in the DHCP message matches the table, the switch forwards the message to the DHCP server. If the information does not match, the switch interprets the client as an unauthorized client and drops the packet. The DHCP snooping switch removes a dynamically-learned DHCP snooping binding entry when one of the following occurs: ● Lease expiry ● DHCP RELEASE packet received from the client ● DHCP DECLINE packet received from the client ● User actions, such as DHCP clear or disabling DHCP snooping You can add a static DHCP snooping binding entry using the CLI. If you add a static entry for a client, any dynamic entry that is present for the same client is overwritten. The switch does not remove static entries if it receives DHCP RELEASE or DHCP DECLINE packets. By default, DHCP snooping is disabled globally and enabled on VLANs. For the DHCP snooping feature to work, enable it globally. NOTE: If you move a DHCP client from an untrusted interface to another untrusted interface within the VLAN, the DHCP snooping binding database is not updated. The switch drops subsequent packets from the client. However, if you move a DHCP client from an untrusted interface to a trusted interface, there is no impact to the traffic from the client. Restrictions for DHCP snooping ● The management VLAN does not support DHCP snooping. ● VxLAN bridges do not support DHCP snooping. ● The maximum number of supported DHCP snooping binding entries is 4000. ● OS10 does not support multi-hop DHCP snooping. ● For the DHCP snooping functionality to work correctly, ensure that the DHCP server supports option 82 (RFC 3046). ● Enable option 82 (RFC 3046) on the DHCP server for the DHCP Snooping functionality to work correctly. Rogue DHCP server detection In the following topology, a trusted DHCP server, a DHCP client, and a rogue DHCP server are connected to the DHCP snooping switch. The DHCP client and DHCP server are on the same VLAN. The physical interface eth 1/1/2 is a trusted interface. When the rogue DHCP server sends a DHCP packet to the client, the switch analyzes the packet. As the rogue server is connected to the switch to an untrusted eth 1/1/3 interface the switch deems the server as a rogue DHCP server and drops the packet. System management 209

Section	Page
Dell EMC SmartFabric OS10 User Guide Release 10.5.1	3
About this guide	27
Conventions	27
Related Documents	27
Documentation Feedback	27
Change history	28
Getting Started with Dell EMC SmartFabric OS10	30
Switch with factory-installed OS10	31
Log in	31
Check OS10 version	32
OS10 upgrade	32
Download OS10 image for upgrade	33
Install OS10 upgrade	33
Install firmware upgrade	35
Upgrade commands	35
boot system	35
image cancel	36
image copy	36
image download	36
image install	37
show boot	38
show image firmware	38
show image status	39
show version	40
Check OS10 license	40
Re-install license	41
Switch without OS installed	41
Uninstall existing OS	42
Download OS10 image	42
Installation using ONIE	43
Automatic installation	44
Manual installation	45
Log in	46
Install OS10 license	46
Downgrade to Release 10.5.0.0 or earlier releases	49
Roll back from 10.5.1.0 or later release to 10.5.0.0 or earlier release	50
Switch deployment options	50
Manual CLI configuration	51
ZTD-automated switch deployment	51
Ansible-automated switch provisioning	51
Feature limitation on the Z9100-ON and S5200-ON series switches	51
Feature limitations on Z9332F-ON switch	51
Remote access	51
Configure Management IP address	52
Configure Management route	52
Configure username and password	53
CLI Basics	54
CONFIGURATION mode	55
Check device status	56
Related Videos	57
Command help	57
Candidate configuration	58
Copy running configuration	61
Restore startup configuration	62
Reload system image	63
Filter show commands	63
Common OS10 commands	64
boot	64
commit	64
configure	64
copy	65
delete	66
dir	67
discard	68
do	68
end	69
exit	69
hostname	69
license	70
lock	70
management route	71
move	71
no	72
ping	72
ping6	74
reload	75
show boot	76
show candidate-configuration	76
show environment	79
show inventory	79
show ip management-route	80
show ipv6 management-route	80
show license status	81
show running-configuration	81
show startup-configuration	84
show system	85
show version	87
start	87
system	87
system-cli disable	88
system-user linuxadmin disable	88
system identifier	89
terminal	89
traceroute	89
unlock	90
username password role	91
write	92
Advanced CLI tasks	93
Command alias	93
Multi-line alias	94
alias	96
alias (multi-line)	97
default (alias)	98
description (alias)	98
line (alias)	98
show alias	99
Batch mode	100
batch	100
Linux shell commands	101
Using OS9 commands	103
feature config-os9-style	103
Dell EMC SmartFabric OS10 zero-touch deployment	104
ZTD DHCP server configuration	106
ZTD provisioning script	106
ZTD CLI batch file	107
Post-ZTD script	108
ZTD commands	108
reload ztd	108
show ztd-status	108
ztd cancel	109
Dell EMC SmartFabric OS10 provisioning	110
Using Ansible	110
Example: Configure an OS10 switch using Ansible	111
System management	114
System banners	114
Login banner	114
Message of the day banner	115
System banner commands	115
banner login	115
banner motd	116
User session management	116
User session management commands	117
exec-timeout	117
kill-session	117
show sessions	118
Telnet server	118
Telnet commands	119
ip telnet server enable	119
ip telnet server vrf	119
Simple Network Management Protocol	119
SNMP security models and levels	120
MIBs	120
SNMPv3	121
SNMP engine ID	122
SNMP groups and users	122
SNMP views	122
Configure SNMP	122
Configure SNMP engine ID	122
Configure SNMP views	123
Configure SNMP groups	123
Configure SNMP users	124
Generate SNMPv3 localized keys	125
Configure SNMP traps	125
Configure SNMP informs	126
SNMP commands	126
show snmp community	126
show snmp engineID	127
show snmp group	127
show snmp user	127
show snmp view	128
snmp-server community	128
snmp-server contact	129
snmp-server enable traps	129
snmp-server engineID	130
snmp-server group	131
snmp-server host	132
snmp-server location	133
snmp-server user	133
snmp-server view	134
snmp-server vrf	135
Example: Configure SNMP	135
System clock	136
Time zones and UTC offset reference	137
System Clock commands	153
clock set	153
clock timezone	154
show clock	154
show clock timezone	154
Network Time Protocol	155
Enable NTP	156
Broadcasts	156
Source IP address	157
Authentication	157
Sample NTP configuration	158
NTP commands	161
ntp authenticate	161
ntp authentication-key	161
ntp broadcast client	162
ntp disable	162
ntp enable vrf	162
ntp master	163
ntp server	163
ntp source	163
ntp trusted-key	164
show ntp associations	164
show ntp status	165
Precision Time Protocol	166
Supported platforms	169
PTP installation scale and limits	169
Configuration notes	169
Configure Precision Time Protocol	170
View PTP information	173
Example: Configure boundary clock with L2 transport method	175
Example: Configure boundary clock with IPv4 multicast transport method	176
Example: Configure boundary clock with IPv4 unicast transport method	176
Example: Configure end-to-end transparent clock	177
Example: Configure boundary clock with IPv4 unicast transport method and L3 VLAN	178
Example: Configure PTP in a multinode setup	179
PTP commands	186
clear ptp counters	186
debug ptp	186
master	187
ptp announce	187
ptp clock	188
ptp delay-mechanism	188
ptp delay-req-min-interval	189
ptp domain	189
ptp enable	189
ptp local-priority	190
ptp priority1	190
ptp priority2	191
ptp role	191
ptp source	191
ptp sync-interval	192
ptp system-time enable	192
ptp transport	193
ptp vlan	194
show ptp	194
show ptp clock	195
show ptp counters	196
show ptp foreign-masters	197
show ptp interface	197
show ptp parent	198
show ptp peer	198
show ptp servo	199
show ptp time-properties	200
slave	200
source	201
Dynamic Host Configuration Protocol	201
Packet format and options	203
DHCP server	204
Automatic address allocation	204
Hostname resolution	206
Manual binding entries	206
View DHCP Information	208
DHCP relay agent	208
Option 82 for security	208
DHCP snooping	208
DHCP snooping examples	213
DHCP snooping switch as a relay agent	215
DHCP snooping in a Layer 2 VLT setup	216
DHCP snooping with DHCP relay agent in a VLT setup	219
Dynamic ARP inspection	222
Source Address Validation	224
System domain name and list	225
DHCP commands	226
DHCP relay commands	226
ip helper-address	226
ipv6 helper-address	227
ip dhcp-relay information-option	227
show vlt mismatch	228
DHCP server commands	232
default-router address	232
disable	232
domain-name	232
dns-server address	233
hardware-address	233
host	233
ip dhcp server	234
lease	234
netbios-name-server address	234
netbios-node-type	235
network	235
pool	235
range	236
show ip dhcp binding	236
DHCP snooping commands	237
arp inspection	237
arp inspection-trust	237
arp inspection violation logging	237
clear ip arp inspection statistics	238
clear ip dhcp snooping binding	238
ip dhcp snooping (global)	238
ip dhcp snooping (interface)	239
ip dhcp snooping binding	239
ip dhcp snooping trust	240
ip dhcp snooping verify mac-address	240
show ip arp inspection database	241
show ip arp inspection statistics	241
show ip arp inspection logging	241
show ip dhcp snooping binding	242
DNS commands	242
ip domain-list	242
ip domain-name	243
ip host	243
ip name-server	243
show hosts	244
Containers	244
Interfaces	247
Ethernet interfaces	247
Unified port groups	248
Z9264F-ON port-group profiles	249
Port-groups on S5200F-ON switches	250
L2 mode configuration	257
L3 mode configuration	258
Fibre Channel interfaces	259
Configuring wavelength	260
Management interface	261
Management interface	261
VLAN interfaces	261
User-configured default VLAN	262
VLAN scale profile	262
Loopback interfaces	263
Port-channel interfaces	264
Create port-channel	264
Add port member	264
Minimum links	265
Assign Port Channel IP Address	265
Remove or disable port-channel	266
Load balance traffic	266
Change hash algorithm	267
Configure interface ranges	267
Switch-port profiles	268
S4148-ON Series port profiles	269
S4148U-ON port profiles	269
Configure negotiation modes on interfaces	270
Configure breakout mode	272
Breakout auto-configuration	272
Reset default configuration	273
Forward error correction	274
Energy-efficient Ethernet	275
Enable energy-efficient Ethernet	276
Clear EEE counters	276
View EEE status/statistics	276
EEE commands	277
clear counters interface eee	277
clear counters interface ethernet eee	278
eee	278
show interface eee	278
show interface eee statistics	279
show interface ethernet eee	279
show interface ethernet eee statistics	279
View interface configuration	280
Digital optical monitoring	283
Enable DOM and DOM traps	284
Default MTU Configuration	285
Interface commands	286
channel-group	286
default interface	286
default vlan-id	289
description (Interface)	289
duplex	290
enable dom	290
enable dom traps	290
feature auto-breakout	291
fec	291
interface breakout	292
interface ethernet	292
interface loopback	293
interface mgmt	293
interface null	293
interface port-channel	294
interface range	294
interface vlan	295
link-bundle-utilization	295
mode	295
mode l3	296
mtu	297
negotiation	297
port mode Eth	298
port-group	299
profile	299
scale-profile vlan	300
show discovered-expanders	300
show interface	301
show interface transceiver “Tunable wavelength”	303
show inventory media	303
show link-bundle-utilization	304
show port-channel summary	305
show port-group	305
show switch-port-profile	306
show system	307
show unit-provision	307
show vlan	308
shutdown	308
speed (Fibre Channel)	309
speed (Management)	309
switch-port-profile	310
switchport access vlan	312
switchport mode	312
switchport trunk allowed vlan	313
unit-provision	313
wavelength	313
default mtu	314
show default mtu	314
PowerEdge MX Ethernet I/O modules	315
Operating modes	315
Changing operating modes	317
Restrictions	317
Port groups on I/O modules	317
Double-density QSFP28 interfaces	317
Virtual ports	320
Single-density QSFP28 interfaces	323
Server-facing interfaces	324
Replace MX Ethernet I/O modules	325
Deployment instructions	325
Replace an IOM in Full-Switch VLT	326
Replace an IOM in SmartFabric	326
Remove and replace the faulty IOM	326
Verify and configure IOM settings	326
Identify the master IOM	327
Log in to the master IOM from the member	328
Initiate the module replacement workflow	328
Connect the new IOM	329
MX-IOM Hardware Replacement	329
View SmartFabric Services configuration	329
Fibre Channel	331
Fibre Channel over Ethernet	332
Configure FIP snooping	333
Terminology	334
Virtual fabric	334
Fibre Channel zoning	337
F_Port on Ethernet	338
Pinning FCoE traffic to a specific port of a port-channel	339
Sample FSB configuration on VLT network	341
Sample FC Switch configuration on VLT network	343
Sample FSB configuration on non-VLT network	345
Sample FC Switch configuration on non-VLT network	346
Multiswitch fabric (E Port)	348
Configure multiswitch fabric (E Port)	350
Verify multiswitch fabric (E Port) configuration	352
Multiswitch fabric (E Port) CLI commands	357
show fc fspf interface	357
clear fc fabric statistics	358
clear fc flow-control-statistics	358
clear fc fspf statistics	359
clear fc ns switch statistics	359
domain-id	359
e_d_tov	360
fc port-mode F \| E	360
feature fc	361
fspf cost	361
fspf dead-interval	362
fspf hello-interval	362
fspf hold-time	362
fspf retransmit-interval	363
principal-priority	363
r_a_tov	364
show fc fabric	364
show fc fabric interface	365
show fc fabric statistics	365
show fc flow-control-statistics	366
show fc fspf database	367
show fc fspf neighbor	367
show fc fspf route	368
show fc ns fabric	368
show fc ns fabric brief	369
show fc ns switch statistics	369
show fc switch	370
show interface fibre channel	370
show vfabric	371
show vfabric fspf	372
Multi-hop FIP-snooping bridge	372
Configuration notes	373
Configure multi-hop FSB	373
Verify multi-hop FSB configuration	379
Sample Multi-hop FSB configuration	380
Configuration guidelines	393
NPIV Proxy Gateway cascading	394
Support for untagged VLAN in FCoE	396
Rebalance FC sessions (NPG)	396
Load balancing after system reboot	397
NPG rebalance topology	397
NPG switch configurations	397
Example: Manual rebalance trigger	399
Equivalent RESTCONF request for the rebalancing CLIs	401
F_Port commands	401
fc alias	402
fc zone	402
fc zoneset	402
feature fc	403
member (alias)	403
member (zone)	404
member (zoneset)	404
show fc alias	404
show fc interface-area-id mapping	405
show fc ns switch	405
show fc zone	406
show fc zoneset	406
zone default-zone permit	408
zoneset activate	408
NPG commands	408
fc port-mode F	408
feature fc npg	409
show npg devices	409
show npg uplink-interface	410
F_Port and NPG commands	411
clear fc statistics	412
fcoe	412
fcoe delay fcf-adv	412

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1,009
1,010
1,011
1,012
1,013
1,014
1,015
1,016
1,017
1,018
1,019
1,020
1,021
1,022
1,023
1,024
1,025
1,026
1,027
1,028
1,029
1,030
1,031
1,032
1,033
1,034
1,035
1,036
1,037
1,038
1,039
1,040
1,041
1,042
1,043
1,044
1,045
1,046
1,047
1,048
1,049
1,050
1,051
1,052
1,053
1,054
1,055
1,056
1,057
1,058
1,059
1,060
1,061
1,062
1,063
1,064
1,065
1,066
1,067
1,068
1,069
1,070
1,071
1,072
1,073
1,074
1,075
1,076
1,077
1,078
1,079
1,080
1,081
1,082
1,083
1,084
1,085
1,086
1,087
1,088
1,089
1,090
1,091
1,092
1,093
1,094
1,095
1,096
1,097
1,098
1,099
1,100
1,101
1,102
1,103
1,104
1,105
1,106
1,107
1,108
1,109
1,110
1,111
1,112
1,113
1,114
1,115
1,116
1,117
1,118
1,119
1,120
1,121
1,122
1,123
1,124
1,125
1,126
1,127
1,128
1,129
1,130
1,131
1,132
1,133
1,134
1,135
1,136
1,137
1,138
1,139
1,140
1,141
1,142
1,143
1,144
1,145
1,146
1,147
1,148
1,149
1,150
1,151
1,152
1,153
1,154
1,155
1,156
1,157
1,158
1,159
1,160
1,161
1,162
1,163
1,164
1,165
1,166
1,167
1,168
1,169
1,170
1,171
1,172
1,173
1,174
1,175
1,176
1,177
1,178
1,179
1,180
1,181
1,182
1,183
1,184
1,185
1,186
1,187
1,188
1,189
1,190
1,191
1,192
1,193
1,194
1,195
1,196
1,197
1,198
1,199
1,200
1,201
1,202
1,203
1,204
1,205
1,206
1,207
1,208
1,209
1,210
1,211
1,212
1,213
1,214
1,215
1,216
1,217
1,218
1,219
1,220
1,221
1,222
1,223
1,224
1,225
1,226
1,227
1,228
1,229
1,230
1,231
1,232
1,233
1,234
1,235
1,236
1,237
1,238
1,239
1,240
1,241
1,242
1,243
1,244
1,245
1,246
1,247
1,248
1,249
1,250
1,251
1,252
1,253
1,254
1,255
1,256
1,257
1,258
1,259
1,260
1,261
1,262
1,263
1,264
1,265
1,266
1,267
1,268
1,269
1,270
1,271
1,272
1,273
1,274
1,275
1,276
1,277
1,278
1,279
1,280
1,281
1,282
1,283
1,284
1,285
1,286
1,287
1,288
1,289
1,290
1,291
1,292
1,293
1,294
1,295
1,296
1,297
1,298
1,299
1,300
1,301
1,302
1,303
1,304
1,305
1,306
1,307
1,308
1,309
1,310
1,311
1,312
1,313
1,314
1,315
1,316
1,317
1,318
1,319
1,320
1,321
1,322
1,323
1,324
1,325
1,326
1,327
1,328
1,329
1,330
1,331
1,332
1,333
1,334
1,335
1,336
1,337
1,338
1,339
1,340
1,341
1,342
1,343
1,344
1,345
1,346
1,347
1,348
1,349
1,350
1,351
1,352
1,353
1,354
1,355
1,356
1,357
1,358
1,359
1,360
1,361
1,362
1,363
1,364
1,365
1,366
1,367
1,368
1,369
1,370
1,371
1,372
1,373
1,374
1,375
1,376
1,377
1,378
1,379
1,380
1,381
1,382
1,383
1,384
1,385
1,386
1,387
1,388
1,389
1,390
1,391
1,392
1,393
1,394
1,395
1,396
1,397
1,398
1,399
1,400
1,401
1,402
1,403
1,404
1,405
1,406
1,407
1,408
1,409
1,410
1,411
1,412
1,413
1,414
1,415
1,416
1,417
1,418
1,419
1,420
1,421
1,422
1,423
1,424
1,425
1,426
1,427
1,428
1,429
1,430
1,431
1,432
1,433
1,434
1,435
1,436
1,437
1,438
1,439
1,440
1,441
1,442
1,443
1,444
1,445
1,446
1,447
1,448
1,449
1,450
1,451
1,452
1,453
1,454
1,455
1,456
1,457
1,458
1,459
1,460
1,461
1,462
1,463
1,464
1,465
1,466
1,467
1,468
1,469
1,470
1,471
1,472
1,473
1,474
1,475
1,476
1,477
1,478
1,479
1,480
1,481
1,482
1,483
1,484
1,485
1,486
1,487
1,488
1,489
1,490
1,491
1,492
1,493
1,494
1,495
1,496
1,497
1,498
1,499
1,500
1,501
1,502
1,503
1,504
1,505
1,506
1,507
1,508
1,509
1,510
1,511
1,512
1,513
1,514
1,515
1,516
1,517
1,518
1,519
1,520
1,521
1,522
1,523
1,524
1,525
1,526
1,527
1,528
1,529
1,530
1,531
1,532
1,533
1,534
1,535
1,536
1,537
1,538
1,539
1,540
1,541
1,542
1,543
1,544
1,545
1,546
1,547
1,548
1,549
1,550
1,551
1,552
1,553
1,554
1,555
1,556
1,557
1,558
1,559
1,560
1,561
1,562
1,563
1,564
1,565
1,566
1,567
1,568
1,569
1,570
1,571
1,572
1,573
1,574
1,575
1,576
1,577
1,578
1,579
1,580
1,581
1,582
1,583
1,584
1,585
1,586
1,587
1,588
1,589
1,590
1,591
1,592
1,593
1,594
1,595
1,596
1,597

Match case Limit results 1 per page

When a switch receives DHCP renew, release, or decline messages from a client, it checks the DHCP snooping binding table for

a match. If the information in the DHCP message matches the table, the switch forwards the message to the DHCP server. If

the information does not match, the switch interprets the client as an unauthorized client and drops the packet.

The DHCP snooping switch removes a dynamically-learned DHCP snooping binding entry when one of the following occurs:

●

Lease expiry

●

DHCP RELEASE packet received from the client

●

DHCP DECLINE packet received from the client

●

User actions, such as DHCP clear or disabling DHCP snooping

You can add a static DHCP snooping binding entry using the CLI. If you add a static entry for a client, any dynamic entry that is

present for the same client is overwritten. The switch does not remove static entries if it receives DHCP RELEASE or DHCP

DECLINE packets.

By default, DHCP snooping is disabled globally and enabled on VLANs. For the DHCP snooping feature to work, enable it

globally.

NOTE:

If you move a DHCP client from an untrusted interface to another untrusted interface within the VLAN, the DHCP

snooping binding database is not updated. The switch drops subsequent packets from the client. However, if you move a

DHCP client from an untrusted interface to a trusted interface, there is no impact to the traffic from the client.

Restrictions for DHCP snooping

●

The management VLAN does not support DHCP snooping.

●

VxLAN bridges do not support DHCP snooping.

●

The maximum number of supported DHCP snooping binding entries is 4000.

●

OS10 does not support multi-hop DHCP snooping.

●

For the DHCP snooping functionality to work correctly, ensure that the DHCP server supports option 82 (RFC 3046).

●

Enable option 82 (RFC 3046) on the DHCP server for the DHCP Snooping functionality to work correctly.

Rogue DHCP server detection

In the following topology, a trusted DHCP server, a DHCP client, and a rogue DHCP server are connected to the DHCP

snooping switch. The DHCP client and DHCP server are on the same VLAN. The physical interface eth 1/1/2 is a trusted

interface. When the rogue DHCP server sends a DHCP packet to the client, the switch analyzes the packet. As the rogue server

is connected to the switch to an untrusted eth 1/1/3 interface the switch deems the server as a rogue DHCP server and drops

the packet.

System management

209