Dell PowerSwitch S4128F-ON EMC SmartFabric OS10 User Guide Release 10.5.1 - Page 208
View DHCP Information, DHCP relay agent, Option 82 for security, DHCP snooping
View all Dell PowerSwitch S4128F-ON manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 208 highlights
View DHCP Information Use the show ip dhcp binding command to view the DHCP binding table entries. OS10# show ip dhcp binding IP Address Hardware address Lease expiration Hostname 11.1.1.254 00:00:12:12:12:12 Jan 27 2016 06:23:45 Total Number of Entries in the Table = 1 DHCP relay agent A DHCP relay agent relays DHCP messages to and from a remote DHCP server, even if the client and server are on different IP networks. You can configure the IP address of the remote DHCP server. You can configure a device either as a DHCP server or a DHCP relay agent - but not both. If routes are not leaked between VRFs, the DHCP relay agent supports multi-virtual routing and forwarding (VRF) instances. The client-facing and server-facing interfaces must be in the same VRF. NOTE: DHCP relay implementation supports IPv4 and IPv6 addresses. Option 82 for security DHCP, as defined by RFC 2131, provides no authentication or security mechanisms. To ensure security, the DHCP relay agent supports Option-82 with the Circuit ID sub-option, which is the printable name of the interface where the client request was received. This option secures all DHCP traffic that goes through a DHCP relay agent, and ensures that communication between the DHCP relay agent and the DHCP server is not compromised. The DHCP relay agent inserts Option 82 before forwarding DHCP packets to the DHCP server. The DHCP server includes Option 82 back in its response to the relay agent. The relay agent uses this information to forward a reply out the interface on which the request was received rather than flooding it on the entire VLAN. However, the relay agent removes Option 82 from its DHCP responses before forwarding the responses to the client. NOTE: Option 82 is supported, but not configurable. DHCP snooping DHCP snooping is a layer 2 security feature that helps networking devices to monitor DHCP messages and block untrusted or rogue DHCP servers. When you enable DHCP snooping on a switch, it begins monitoring transactions between trusted DHCP servers and DHCP clients and uses the information to build the DHCP snooping binding table. You configure interfaces that connect to DHCP servers as trusted interfaces. All other interfaces are untrusted by default. The DHCP snooping binding table contains the following information: ● Client IP addresses ● Client MAC addresses ● Interface facing the clients ● Client VLAN ● Lease time ● DHCP binding type - static or dynamic The switch considers DHCP servers connected to trusted interfaces on the switch as legitimate servers. When a switch receives DHCP server-initiated packets (UDP destination port 67) on an untrusted interface, it drops the packet. 208 System management
-
1
-
2
-
3
-
4
-
5
-
6
-
7
-
8
-
9
-
10
-
11
-
12
-
13
-
14
-
15
-
16
-
17
-
18
-
19
-
20
-
21
-
22
-
23
-
24
-
25
-
26
-
27
-
28
-
29
-
30
-
31
-
32
-
33
-
34
-
35
-
36
-
37
-
38
-
39
-
40
-
41
-
42
-
43
-
44
-
45
-
46
-
47
-
48
-
49
-
50
-
51
-
52
-
53
-
54
-
55
-
56
-
57
-
58
-
59
-
60
-
61
-
62
-
63
-
64
-
65
-
66
-
67
-
68
-
69
-
70
-
71
-
72
-
73
-
74
-
75
-
76
-
77
-
78
-
79
-
80
-
81
-
82
-
83
-
84
-
85
-
86
-
87
-
88
-
89
-
90
-
91
-
92
-
93
-
94
-
95
-
96
-
97
-
98
-
99
-
100
-
101
-
102
-
103
-
104
-
105
-
106
-
107
-
108
-
109
-
110
-
111
-
112
-
113
-
114
-
115
-
116
-
117
-
118
-
119
-
120
-
121
-
122
-
123
-
124
-
125
-
126
-
127
-
128
-
129
-
130
-
131
-
132
-
133
-
134
-
135
-
136
-
137
-
138
-
139
-
140
-
141
-
142
-
143
-
144
-
145
-
146
-
147
-
148
-
149
-
150
-
151
-
152
-
153
-
154
-
155
-
156
-
157
-
158
-
159
-
160
-
161
-
162
-
163
-
164
-
165
-
166
-
167
-
168
-
169
-
170
-
171
-
172
-
173
-
174
-
175
-
176
-
177
-
178
-
179
-
180
-
181
-
182
-
183
-
184
-
185
-
186
-
187
-
188
-
189
-
190
-
191
-
192
-
193
-
194
-
195
-
196
-
197
-
198
-
199
-
200
-
201
-
202
-
203
-
204
-
205
-
206
-
207
-
208
-
209
-
210
-
211
-
212
-
213
-
214
-
215
-
216
-
217
-
218
-
219
-
220
-
221
-
222
-
223
-
224
-
225
-
226
-
227
-
228
-
229
-
230
-
231
-
232
-
233
-
234
-
235
-
236
-
237
-
238
-
239
-
240
-
241
-
242
-
243
-
244
-
245
-
246
-
247
-
248
-
249
-
250
-
251
-
252
-
253
-
254
-
255
-
256
-
257
-
258
-
259
-
260
-
261
-
262
-
263
-
264
-
265
-
266
-
267
-
268
-
269
-
270
-
271
-
272
-
273
-
274
-
275
-
276
-
277
-
278
-
279
-
280
-
281
-
282
-
283
-
284
-
285
-
286
-
287
-
288
-
289
-
290
-
291
-
292
-
293
-
294
-
295
-
296
-
297
-
298
-
299
-
300
-
301
-
302
-
303
-
304
-
305
-
306
-
307
-
308
-
309
-
310
-
311
-
312
-
313
-
314
-
315
-
316
-
317
-
318
-
319
-
320
-
321
-
322
-
323
-
324
-
325
-
326
-
327
-
328
-
329
-
330
-
331
-
332
-
333
-
334
-
335
-
336
-
337
-
338
-
339
-
340
-
341
-
342
-
343
-
344
-
345
-
346
-
347
-
348
-
349
-
350
-
351
-
352
-
353
-
354
-
355
-
356
-
357
-
358
-
359
-
360
-
361
-
362
-
363
-
364
-
365
-
366
-
367
-
368
-
369
-
370
-
371
-
372
-
373
-
374
-
375
-
376
-
377
-
378
-
379
-
380
-
381
-
382
-
383
-
384
-
385
-
386
-
387
-
388
-
389
-
390
-
391
-
392
-
393
-
394
-
395
-
396
-
397
-
398
-
399
-
400
-
401
-
402
-
403
-
404
-
405
-
406
-
407
-
408
-
409
-
410
-
411
-
412
-
413
-
414
-
415
-
416
-
417
-
418
-
419
-
420
-
421
-
422
-
423
-
424
-
425
-
426
-
427
-
428
-
429
-
430
-
431
-
432
-
433
-
434
-
435
-
436
-
437
-
438
-
439
-
440
-
441
-
442
-
443
-
444
-
445
-
446
-
447
-
448
-
449
-
450
-
451
-
452
-
453
-
454
-
455
-
456
-
457
-
458
-
459
-
460
-
461
-
462
-
463
-
464
-
465
-
466
-
467
-
468
-
469
-
470
-
471
-
472
-
473
-
474
-
475
-
476
-
477
-
478
-
479
-
480
-
481
-
482
-
483
-
484
-
485
-
486
-
487
-
488
-
489
-
490
-
491
-
492
-
493
-
494
-
495
-
496
-
497
-
498
-
499
-
500
-
501
-
502
-
503
-
504
-
505
-
506
-
507
-
508
-
509
-
510
-
511
-
512
-
513
-
514
-
515
-
516
-
517
-
518
-
519
-
520
-
521
-
522
-
523
-
524
-
525
-
526
-
527
-
528
-
529
-
530
-
531
-
532
-
533
-
534
-
535
-
536
-
537
-
538
-
539
-
540
-
541
-
542
-
543
-
544
-
545
-
546
-
547
-
548
-
549
-
550
-
551
-
552
-
553
-
554
-
555
-
556
-
557
-
558
-
559
-
560
-
561
-
562
-
563
-
564
-
565
-
566
-
567
-
568
-
569
-
570
-
571
-
572
-
573
-
574
-
575
-
576
-
577
-
578
-
579
-
580
-
581
-
582
-
583
-
584
-
585
-
586
-
587
-
588
-
589
-
590
-
591
-
592
-
593
-
594
-
595
-
596
-
597
-
598
-
599
-
600
-
601
-
602
-
603
-
604
-
605
-
606
-
607
-
608
-
609
-
610
-
611
-
612
-
613
-
614
-
615
-
616
-
617
-
618
-
619
-
620
-
621
-
622
-
623
-
624
-
625
-
626
-
627
-
628
-
629
-
630
-
631
-
632
-
633
-
634
-
635
-
636
-
637
-
638
-
639
-
640
-
641
-
642
-
643
-
644
-
645
-
646
-
647
-
648
-
649
-
650
-
651
-
652
-
653
-
654
-
655
-
656
-
657
-
658
-
659
-
660
-
661
-
662
-
663
-
664
-
665
-
666
-
667
-
668
-
669
-
670
-
671
-
672
-
673
-
674
-
675
-
676
-
677
-
678
-
679
-
680
-
681
-
682
-
683
-
684
-
685
-
686
-
687
-
688
-
689
-
690
-
691
-
692
-
693
-
694
-
695
-
696
-
697
-
698
-
699
-
700
-
701
-
702
-
703
-
704
-
705
-
706
-
707
-
708
-
709
-
710
-
711
-
712
-
713
-
714
-
715
-
716
-
717
-
718
-
719
-
720
-
721
-
722
-
723
-
724
-
725
-
726
-
727
-
728
-
729
-
730
-
731
-
732
-
733
-
734
-
735
-
736
-
737
-
738
-
739
-
740
-
741
-
742
-
743
-
744
-
745
-
746
-
747
-
748
-
749
-
750
-
751
-
752
-
753
-
754
-
755
-
756
-
757
-
758
-
759
-
760
-
761
-
762
-
763
-
764
-
765
-
766
-
767
-
768
-
769
-
770
-
771
-
772
-
773
-
774
-
775
-
776
-
777
-
778
-
779
-
780
-
781
-
782
-
783
-
784
-
785
-
786
-
787
-
788
-
789
-
790
-
791
-
792
-
793
-
794
-
795
-
796
-
797
-
798
-
799
-
800
-
801
-
802
-
803
-
804
-
805
-
806
-
807
-
808
-
809
-
810
-
811
-
812
-
813
-
814
-
815
-
816
-
817
-
818
-
819
-
820
-
821
-
822
-
823
-
824
-
825
-
826
-
827
-
828
-
829
-
830
-
831
-
832
-
833
-
834
-
835
-
836
-
837
-
838
-
839
-
840
-
841
-
842
-
843
-
844
-
845
-
846
-
847
-
848
-
849
-
850
-
851
-
852
-
853
-
854
-
855
-
856
-
857
-
858
-
859
-
860
-
861
-
862
-
863
-
864
-
865
-
866
-
867
-
868
-
869
-
870
-
871
-
872
-
873
-
874
-
875
-
876
-
877
-
878
-
879
-
880
-
881
-
882
-
883
-
884
-
885
-
886
-
887
-
888
-
889
-
890
-
891
-
892
-
893
-
894
-
895
-
896
-
897
-
898
-
899
-
900
-
901
-
902
-
903
-
904
-
905
-
906
-
907
-
908
-
909
-
910
-
911
-
912
-
913
-
914
-
915
-
916
-
917
-
918
-
919
-
920
-
921
-
922
-
923
-
924
-
925
-
926
-
927
-
928
-
929
-
930
-
931
-
932
-
933
-
934
-
935
-
936
-
937
-
938
-
939
-
940
-
941
-
942
-
943
-
944
-
945
-
946
-
947
-
948
-
949
-
950
-
951
-
952
-
953
-
954
-
955
-
956
-
957
-
958
-
959
-
960
-
961
-
962
-
963
-
964
-
965
-
966
-
967
-
968
-
969
-
970
-
971
-
972
-
973
-
974
-
975
-
976
-
977
-
978
-
979
-
980
-
981
-
982
-
983
-
984
-
985
-
986
-
987
-
988
-
989
-
990
-
991
-
992
-
993
-
994
-
995
-
996
-
997
-
998
-
999
-
1,000
-
1,001
-
1,002
-
1,003
-
1,004
-
1,005
-
1,006
-
1,007
-
1,008
-
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