DHCP Snooping WLC

Hi,
I would like to DHCP snooping on the WLC.
Or a method to block DHCP pirate and authorized my DHCP.
Best Regards,
Julien Hernandez.

Here the client 192.168.0.0 :
(Cisco Controller) >show client detail 1c:99:4c:6f:c6:96
Client MAC Address............................... 1c:99:4c:6f:c6:96
Client Username ................................. N/A
AP MAC Address................................... 44:ad:d9:57:fd:20
AP Name.......................................... AP-INDE-106
AP radio slot Id................................. 0
Client State..................................... Associated
Client NAC OOB State............................. Access
Wireless LAN Id.................................. 1
Hotspot (802.11u)................................ Not Supported
BSSID............................................ 44:ad:d9:57:fd:20
Connected For ................................... 8127 secs
Channel.......................................... 11
IP Address....................................... 192.168.0.155
Gateway Address.................................. Unknown
Netmask.......................................... Unknown
Association Id................................... 8
Authentication Algorithm......................... Open System
Reason Code...................................... 1
Status Code...................................... 0
Session Timeout.................................. 15000
Client CCX version............................... No CCX support
QoS Level........................................ Silver
Avg data Rate.................................... 0
Burst data Rate.................................. 0
Avg Real time data Rate.......................... 0
Burst Real Time data Rate........................ 0
802.1P Priority Tag.............................. disabled
CTS Security Group Tag........................... Not Applicable
KTS CAC Capability............................... No
WMM Support...................................... Enabled
APSD ACs....................................... BK BE VI VO
Power Save....................................... ON
Current Rate..................................... m7
Supported Rates.................................. 5.5,11.0,6.0,9.0,12.0,18.0,
............................................. 24.0,36.0,48.0,54.0
Mobility State................................... Local
Mobility Move Count.............................. 0
Security Policy Completed........................ Yes
Policy Manager State............................. RUN
Policy Manager Rule Created...................... Yes
Audit Session ID................................. none
AAA Role Type.................................... none
Local Policy Applied............................. none
IPv4 ACL Name.................................... none
FlexConnect ACL Applied Status................... Unavailable
IPv4 ACL Applied Status.......................... Unavailable
IPv6 ACL Name.................................... none
IPv6 ACL Applied Status.......................... Unavailable
Layer2 ACL Name.................................. none
Layer2 ACL Applied Status........................ Unavailable
mDNS Status...................................... Disabled
mDNS Profile Name................................ none
No. of mDNS Services Advertised.................. 0
Policy Type...................................... N/A
Encryption Cipher................................ None
Protected Management Frame ...................... No
Management Frame Protection...................... No
EAP Type......................................... Unknown
FlexConnect Data Switching....................... Local
FlexConnect Dhcp Status.......................... Local
FlexConnect Vlan Based Central Switching......... No
FlexConnect Authentication....................... Central
Quarantine VLAN.................................. 0
Access VLAN...................................... 321
Client Capabilities:
CF Pollable................................ Not implemented
CF Poll Request............................ Not implemented
Short Preamble............................. Implemented
PBCC....................................... Not implemented
Channel Agility............................ Not implemented
Listen Interval............................ 10
Fast BSS Transition........................ Not implemented
Client Wifi Direct Capabilities:
WFD capable................................ No
Manged WFD capable......................... No
Cross Connection Capable................... No
Support Concurrent Operation............... No
Fast BSS Transition Details:
Client Statistics:
Number of Bytes Received................... 2526655
Number of Bytes Sent....................... 2425132
Total Number of Bytes Sent................. 2425132
Total Number of Bytes Recv................. 2526655
Number of Bytes Sent (last 90s)............ 64
Number of Bytes Recv (last 90s)............ 6764
Number of Packets Received................. 25105
Number of Packets Sent..................... 5996
Number of Interim-Update Sent.............. 0
Number of EAP Id Request Msg Timeouts...... 0
Number of EAP Id Request Msg Failures...... 0
Number of EAP Request Msg Timeouts......... 0
Number of EAP Request Msg Failures......... 0
Number of EAP Key Msg Timeouts............. 0
Number of EAP Key Msg Failures............. 0
Number of Data Retries..................... 1018
Number of RTS Retries...................... 0
Number of Duplicate Received Packets....... 56
Number of Decrypt Failed Packets........... 0
Number of Mic Failured Packets............. 0
Number of Mic Missing Packets.............. 0
Number of RA Packets Dropped............... 0
Number of Policy Errors.................... 0
Radio Signal Strength Indicator............ -60 dBm
Signal to Noise Ratio...................... 24 dB
Client Rate Limiting Statistics:
Number of Data Packets Recieved............ 0
Number of Data Rx Packets Dropped.......... 0
Number of Data Bytes Recieved.............. 0
Number of Data Rx Bytes Dropped............ 0
Number of Realtime Packets Recieved........ 0
Number of Realtime Rx Packets Dropped...... 0
Number of Realtime Bytes Recieved.......... 0
Number of Realtime Rx Bytes Dropped........ 0
Number of Data Packets Sent................ 0
Number of Data Tx Packets Dropped.......... 0
Number of Data Bytes Sent.................. 0
Number of Data Tx Bytes Dropped............ 0
Number of Realtime Packets Sent............ 0
Number of Realtime Tx Packets Dropped...... 0
Number of Realtime Bytes Sent.............. 0
Number of Realtime Tx Bytes Dropped........ 0
Nearby AP Statistics:
AP-INDE-108(slot 0)
antenna0: 5364 secs ago.................. -74 dBm
antenna1: 5364 secs ago.................. -87 dBm
AP-INDE-106(slot 0)
antenna0: 5364 secs ago.................. -67 dBm
antenna1: 5364 secs ago.................. -57 dBm
AP-INDE-106(slot 1)
antenna0: 5363 secs ago.................. -82 dBm
antenna1: 5363 secs ago.................. -87 dBm
AP-INDE-111(slot 0)
antenna0: 5364 secs ago.................. -94 dBm
antenna1: 5364 secs ago.................. -97 dBm
AP-INDE-119(slot 0)
antenna0: 5364 secs ago.................. -87 dBm
antenna1: 5364 secs ago.................. -91 dBm
AP-INDE-105(slot 0)
antenna0: 5364 secs ago.................. -68 dBm
antenna1: 5364 secs ago.................. -79 dBm
AP-INDE-105(slot 1)
antenna0: 5363 secs ago.................. -90 dBm
antenna1: 5363 secs ago.................. -87 dBm
AP-INDE-109(slot 0)
antenna0: 5364 secs ago.................. -75 dBm
antenna1: 5364 secs ago.................. -85 dBm
AP-INDE-109(slot 1)
antenna0: 5364 secs ago.................. -83 dBm
antenna1: 5364 secs ago.................. -78 dBm
AP-INDE-121(slot 0)
antenna0: 14490 secs ago................. -91 dBm
antenna1: 14490 secs ago................. -92 dBm
AP-INDE-126(slot 0)
antenna0: 8132 secs ago.................. -89 dBm
antenna1: 8132 secs ago.................. -92 dBm
AP-INDE-126(slot 1)
antenna0: 38197 secs ago................. -93 dBm
antenna1: 38197 secs ago................. -83 dBm
AP-INDE-116(slot 0)
antenna0: 5364 secs ago.................. -61 dBm
antenna1: 5364 secs ago.................. -50 dBm
AP-INDE-116(slot 1)
antenna0: 5364 secs ago.................. -82 dBm
antenna1: 5364 secs ago.................. -86 dBm
AP-INDE-112(slot 0)
antenna0: 5364 secs ago.................. -71 dBm
antenna1: 5364 secs ago.................. -71 dBm
AP-INDE-112(slot 1)
antenna0: 5364 secs ago.................. -88 dBm
antenna1: 5364 secs ago.................. -90 dBm
AP-INDE-107(slot 0)
antenna0: 8129 secs ago.................. -91 dBm
antenna1: 8129 secs ago.................. -85 dBm
AP-INDE-118(slot 0)
antenna0: 5364 secs ago.................. -94 dBm
antenna1: 5364 secs ago.................. -91 dBm
AP-INDE-114(slot 0)
antenna0: 5364 secs ago.................. -93 dBm
antenna1: 5364 secs ago.................. -85 dBm
AP-INDE-114(slot 1)
antenna0: 38197 secs ago................. -93 dBm
antenna1: 38197 secs ago................. -91 dBm
AP-INDE-123(slot 0)
antenna0: 5364 secs ago.................. -72 dBm
antenna1: 5364 secs ago.................. -83 dBm
AP-INDE-103(slot 0)
antenna0: 5364 secs ago.................. -91 dBm
antenna1: 5364 secs ago.................. -83 dBm
AP-INDE-104(slot 0)
antenna0: 5364 secs ago.................. -87 dBm
antenna1: 5364 secs ago.................. -90 dBm
AP-INDE-102(slot 0)
antenna0: 5364 secs ago.................. -90 dBm
antenna1: 5364 secs ago.................. -87 dBm
DNS Server details:
DNS server IP ............................. 0.0.0.0
DNS server IP ............................. 0.0.0.0
Assisted Roaming Prediction List details:
Client Dhcp Required: True
Allowed (URL)IP Addresses
(Cisco Controller) >show client detail ec:59:e7:e9:e5:68
Client MAC Address............................... ec:59:e7:e9:e5:68
Client Username ................................. N/A
AP MAC Address................................... 44:ad:d9:57:fd:20
AP Name.......................................... AP-INDE-106
AP radio slot Id................................. 0
Client State..................................... Associated
Client NAC OOB State............................. Access
Wireless LAN Id.................................. 1
Hotspot (802.11u)................................ Not Supported
BSSID............................................ 44:ad:d9:57:fd:20
Connected For ................................... 3043 secs
Channel.......................................... 11
IP Address....................................... 192.168.0.162
Gateway Address.................................. Unknown
Netmask.......................................... Unknown
Association Id................................... 4
Authentication Algorithm......................... Open System
Reason Code...................................... 1
Status Code...................................... 0
Session Timeout.................................. 15000
Client CCX version............................... No CCX support
QoS Level........................................ Silver
Avg data Rate.................................... 0
Burst data Rate.................................. 0
Avg Real time data Rate.......................... 0
Burst Real Time data Rate........................ 0
802.1P Priority Tag.............................. disabled
CTS Security Group Tag........................... Not Applicable
KTS CAC Capability............................... No
WMM Support...................................... Enabled
APSD ACs....................................... BK BE VI VO
Power Save....................................... ON
Current Rate..................................... m7
Supported Rates.................................. 5.5,11.0,6.0,9.0,12.0,18.0,
............................................. 24.0,36.0,48.0,54.0
Mobility State................................... Local
Mobility Move Count.............................. 0
Security Policy Completed........................ Yes
Policy Manager State............................. RUN
Policy Manager Rule Created...................... Yes
Audit Session ID................................. none
AAA Role Type.................................... none
Local Policy Applied............................. none
IPv4 ACL Name.................................... none
FlexConnect ACL Applied Status................... Unavailable
IPv4 ACL Applied Status.......................... Unavailable
IPv6 ACL Name.................................... none
IPv6 ACL Applied Status.......................... Unavailable
Layer2 ACL Name.................................. none
Layer2 ACL Applied Status........................ Unavailable
mDNS Status...................................... Disabled
mDNS Profile Name................................ none
No. of mDNS Services Advertised.................. 0
Policy Type...................................... N/A
Encryption Cipher................................ None
Protected Management Frame ...................... No
Management Frame Protection...................... No
EAP Type......................................... Unknown
FlexConnect Data Switching....................... Local
FlexConnect Dhcp Status.......................... Local
FlexConnect Vlan Based Central Switching......... No
FlexConnect Authentication....................... Central
Quarantine VLAN.................................. 0
Access VLAN...................................... 321
Client Capabilities:
CF Pollable................................ Not implemented
CF Poll Request............................ Not implemented
Short Preamble............................. Implemented
PBCC....................................... Not implemented
Channel Agility............................ Not implemented
Listen Interval............................ 1
Fast BSS Transition........................ Not implemented
Client Wifi Direct Capabilities:
WFD capable................................ No
Manged WFD capable......................... No
Cross Connection Capable................... No
Support Concurrent Operation............... No
Fast BSS Transition Details:
Client Statistics:
Number of Bytes Received................... 13499
Number of Bytes Sent....................... 7662
Total Number of Bytes Sent................. 7662
Total Number of Bytes Recv................. 13499
Number of Bytes Sent (last 90s)............ 0
Number of Bytes Recv (last 90s)............ 0
Number of Packets Received................. 184
Number of Packets Sent..................... 69
Number of Interim-Update Sent.............. 0
Number of EAP Id Request Msg Timeouts...... 0
Number of EAP Id Request Msg Failures...... 0
Number of EAP Request Msg Timeouts......... 0
Number of EAP Request Msg Failures......... 0
Number of EAP Key Msg Timeouts............. 0
Number of EAP Key Msg Failures............. 0
Number of Data Retries..................... 61
Number of RTS Retries...................... 0
Number of Duplicate Received Packets....... 2
Number of Decrypt Failed Packets........... 0
Number of Mic Failured Packets............. 0
Number of Mic Missing Packets.............. 0
Number of RA Packets Dropped............... 0
Number of Policy Errors.................... 0
Radio Signal Strength Indicator............ -70 dBm
Signal to Noise Ratio...................... 18 dB
Client Rate Limiting Statistics:
Number of Data Packets Recieved............ 0
Number of Data Rx Packets Dropped.......... 0
Number of Data Bytes Recieved.............. 0
Number of Data Rx Bytes Dropped............ 0
Number of Realtime Packets Recieved........ 0
Number of Realtime Rx Packets Dropped...... 0
Number of Realtime Bytes Recieved.......... 0
Number of Realtime Rx Bytes Dropped........ 0
Number of Data Packets Sent................ 0
Number of Data Tx Packets Dropped.......... 0
Number of Data Bytes Sent.................. 0
Number of Data Tx Bytes Dropped............ 0
Number of Realtime Packets Sent............ 0
Number of Realtime Tx Packets Dropped...... 0
Number of Realtime Bytes Sent.............. 0
Number of Realtime Tx Bytes Dropped........ 0
Nearby AP Statistics:
AP-INDE-120(slot 0)
antenna0: 36159 secs ago................. -98 dBm
antenna1: 36159 secs ago................. -97 dBm
AP-INDE-115(slot 0)
antenna0: 11075 secs ago................. -96 dBm
antenna1: 11075 secs ago................. -96 dBm
AP-INDE-108(slot 0)
antenna0: 188 secs ago................... -96 dBm
antenna1: 188 secs ago................... -95 dBm
AP-INDE-106(slot 0)
antenna0: 188 secs ago................... -78 dBm
antenna1: 188 secs ago................... -67 dBm
AP-INDE-111(slot 0)
antenna0: 1451 secs ago.................. -98 dBm
antenna1: 1451 secs ago.................. -95 dBm
AP-INDE-119(slot 0)
antenna0: 188 secs ago................... -87 dBm
antenna1: 188 secs ago................... -95 dBm
AP-INDE-122(slot 0)
antenna0: 73165 secs ago................. -95 dBm
antenna1: 73165 secs ago................. -95 dBm
AP-INDE-105(slot 0)
antenna0: 188 secs ago................... -85 dBm
antenna1: 188 secs ago................... -86 dBm
AP-INDE-109(slot 0)
antenna0: 332 secs ago................... -91 dBm
antenna1: 332 secs ago................... -89 dBm
AP-INDE-121(slot 0)
antenna0: 2708 secs ago.................. -98 dBm
antenna1: 2708 secs ago.................. -96 dBm
AP-INDE-126(slot 0)
antenna0: 215 secs ago................... -84 dBm
antenna1: 215 secs ago................... -86 dBm
AP-INDE-116(slot 0)
antenna0: 188 secs ago................... -61 dBm
antenna1: 188 secs ago................... -61 dBm
AP-INDE-112(slot 0)
antenna0: 187 secs ago................... -83 dBm
antenna1: 187 secs ago................... -85 dBm
AP-INDE-107(slot 0)
antenna0: 188 secs ago................... -89 dBm
antenna1: 188 secs ago................... -90 dBm
AP-INDE-118(slot 0)
antenna0: 188 secs ago................... -95 dBm
antenna1: 188 secs ago................... -98 dBm
AP-INDE-114(slot 0)
antenna0: 187 secs ago................... -83 dBm
antenna1: 187 secs ago................... -85 dBm
AP-INDE-113(slot 0)
antenna0: 38981 secs ago................. -94 dBm
antenna1: 38981 secs ago................. -95 dBm
AP-INDE-123(slot 0)
antenna0: 187 secs ago................... -73 dBm
antenna1: 187 secs ago................... -65 dBm
AP-INDE-117(slot 0)
antenna0: 11013 secs ago................. -94 dBm
antenna1: 11013 secs ago................. -97 dBm
AP-INDE-103(slot 0)
antenna0: 187 secs ago................... -70 dBm
antenna1: 187 secs ago................... -80 dBm
AP-INDE-104(slot 0)
antenna0: 214 secs ago................... -95 dBm
antenna1: 214 secs ago................... -91 dBm
AP-INDE-102(slot 0)
antenna0: 215 secs ago................... -87 dBm
antenna1: 215 secs ago................... -88 dBm
AP-INDE-100(slot 0)
antenna0: 11014 secs ago................. -96 dBm
antenna1: 11014 secs ago................. -96 dBm
AP-INDE-101(slot 0)
antenna0: 11013 secs ago................. -96 dBm
antenna1: 11013 secs ago................. -95 dBm
DNS Server details:
DNS server IP ............................. 0.0.0.0
DNS server IP ............................. 0.0.0.0
Assisted Roaming Prediction List details:
Client Dhcp Required: True
Allowed (URL)IP Addresses

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Total Attempts       :        0   Startup Failures :        0
Successful Transfers :        0   Failed Transfers :        0
Successful Reads     :        0   Failed Reads     :        0
Successful Writes    :        0   Failed Writes    :        0
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Last Succeded Time : 07:18:07 EDT Wed Jun 15 2011
Last Failed Time : None
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Total Attempts       :       13   Startup Failures :        0
Successful Transfers :       13   Failed Transfers :        0
Successful Reads     :        0   Failed Reads     :        0
Successful Writes    :       13   Failed Writes    :        0
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Switch DHCP snooping is enabled
DHCP snooping is configured on following VLANs: Q,W,E,RT,TY,Y
Insertion of option 82 is enabled
Option 82 on untrusted port is not allowed
Verification of hwaddr field is enabled
Verification of giaddr field is enabled
Interface Trusted Rate limit (pps)
GigabitEthernetX/X yes unlimited
Port-channel    yes unlimited
port config port-channel
ip arp inspection trust
ip dhcp snooping trust
2960 config
Switch DHCP snooping is enabled
DHCP snooping is configured on following VLANs:Q
Insertion of option 82 is disabled
circuit-id default format: vlan-mod-port
remote-id: 1111:1111:1111 (MAC)
Option 82 on untrusted port is not allowed
Verification of hwaddr field is enabled
Verification of giaddr field is enabled
DHCP snooping trust/rate is configured on the following Interfaces:
Interface Trusted Allow option Rate limit (pps)
Port-channel yes yes unlimited
port config
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Hi Bonnie, as far as I know DHCP snooping is not on the SX200 switch.I also am unable to find documentation within release notes and the admin guide stating it does.

C2950 IOS for DHCP Snooping and DAI

hi all,
anyone knows what image i would need for my 2950 to enable DHCP snooping and DAI features (just for lab purpose)?
or are these features just available on the bigger modular switches (4500 and 6500)?
>sh ver
Cisco Internetwork Operating System Software
IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(22)EA8a, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2006 by cisco Systems, Inc.
Compiled Fri 28-Jul-06 15:16 by weiliu
Image text-base: 0x80010000, data-base: 0x8056A000
Switch(config)#ip dhcp snooping ?
information DHCP Snooping information
vlan DHCP Snooping vlan
<cr>
Switch(config)#ip arp ?
% Unrecognized command

Hi Alain,
Thanks for this info! I've read you're CCNA Security.
Just curious, are you gonna write your CCNP Security soon?
Could you recommend a good lab switch for SECURE?
Sent from Cisco Technical Support iPad App

Help understanding DHCP Snooping and Dynamic ARP Inspection

Please help me to understand DHCP Snooping and Dynamic ARP Inspection.

HI Ezra,
In simple words:
DHCP Snooping is a feature which is available on switches. This feature is used to prevent rogue dhcp server attacks.
In the diagram, a valid dhcp server is connected to the network. The computers are suppose to receive dynamic ip addresses from the valid server. An attacker implants a rogue dhcp server on the network as shown in the diagram. The following steps are followed for a client to receive an ip address from a dhcp server.
When a client (computer) is connected to the switch and is configured to receive a dynamic ip address from a dhcp server, the dhcp service on the client, sends out a DHCP Discover packet, searching for servers on the network. This packet is broadcast in nature. DHCP servers on the network, would respond to the DHCP Discover packet sent from the client. In the example, both the DHCP servers would respond to the DHCP discover packet. The client would process the first packet it receives. If the response send by the rogue dhcp server reaches the client first, then the computer would have an ip address provided by the rogue dhcp server.
To prevent this, dhcp snooping is configured on the port on which the valid dhcp server is connected to. After the configuration is performed, no other ports on the switch would be able to respond to DHCP Discover packets from the clients. So even through the attacker has set up a rogue dhcp server, the port on the switch to which the attacker has connected would not be allowed to respond to DHCP discover packets. Thus dhcp snooping thwarts the attempt from the attacker in setting up a rogue dhcp server.
DAI:
Please read the expalined version from here: http://ciscocertstudyblog.blogspot.de/2010/06/ciscoblogpics.html
More about DHCP snooping and DAI: Please read this attached document with some detailed explanation.
Hope it helps.
Regards
Please use rating system and mark athe question answered it may help others.

Illegal dhcp (DHCP Snooping )

hi,
in my network , where there is a dhcp (i use dhcp relay on my layer 3 switch),
often someone connect a pc with a service of dhcp service active , and this produces a problem.
i read in cisco.com and i find the documentation about how to fix this problem.
DHCP Snooping is the solution.
The release on my cisco 6509 with msfc2 not support this feature.
WHAT DO YOU THINK ABOUT IT ?
HAVE YOU A LINK WITH AN EXAMPLE OF ALTERNATIVE METHODS?
Thanks
FC

my version are:
IOS (tm) MSFC2 Software (C6MSFC2-JSV-M), Version 12.1(11b)E4
in CAT OS
WS-C6509 Software, Version NmpSW: 7.6(8)
Step 1. (Permit DHCP response from host 1.2.3.4). "set security acl ip SERVER permit udp host 1.2.3.4 any eq 68"
Step 2. (Deny DHCP responses from any other host). "set security acl ip SERVER deny udp any any eq 68"
Step 3. (Permit other IP traffic). "set security acl ip SERVER permit any any"
Step 4.(Commit the VACL)."commit security acl SERVER"
Step 5.(Map the VACL to VLAN 10 for example). "set security acl map SERVER 10"
WHAT DO YOU THINK ABOUT MY CONFIGURATION?
Thanks
FC

SGE2010P - DHCP Snooping - VLANs - Web GUI

Model: SGE2010P
FW: 3.0.0.18
In the web GUI:
Under DHCP Snooping ---> VLAN Settings
It does not allow you to enter a VLAN higher than 4092
I configured it to listen on VLAN 4094 via the CLI just fine.
I believe this should be fixed in the web GUI.

Yeah, I don't think I want to do that because of all the little troubleshooting steps they usually make me go through.
I buy high-end equipment so I can skip the simple stuff...they usually don't understand that.
I know it's a bug because I've already done the troubleshooting, I don't feel I should have to do the same stuff again.
I only make a call when absolutely necessary because I find the phone support for this product line very un-supportative.
At this level, I think I should get to skip the simple stuff.
If you can't submit a bug report thats fine, I'll just leave it at this.
It's no big deal, I just thought I'd let some one else know.

Nexus DHCP Snooping save database?

Is there a way save the DHCP snooping database on Nexus7K or 5K, either to flash or server? Without this, wouldn't DAI and IP Source Guard be triggered by normal traffic after a reboot?

Hi Sunil, that was the last idea I had got.
The one before the last was write on this support forum.
So I tried everythink but reboot. Which is little bit strange solution.
Thank you.

Configuring DHCP snooping

I am settting up DHCP snooping for the first time on an 3750. My DHCP server resides on another switch. The 3750 is connected through a Gig SFP fiber to a 3550 with DHCP relay.
Is the following config correct? The client will not get a dhcp with the option 82 enabled.
(config)#ip dhcp snooping
(config)#ip dhcp snooping vlan 2-200
(config)#no ip dhcp snooping info option
!The client will not get an ip with
!this option enabled.
! trusted interface connected to the 3550
(config)#int gi1/0/4
(config-if)#ip dhcp trust
! untrusted interface
(config-if)#ip dhcp limit rate 100
(config)#ip dhcp snooping database flash:/database1
(config)#ip dhcp snooping database timeout 30
(config)#ip dhcp snooping database write-delay 30

Have you enabled option 82 on your DHCP server? Also, on your DHCP relay switch, configure the following under the VLAN interface in question and see if it makes any difference.
Example:
c3550-A(config)#int vlan 1
c3550-A(config-if)#ip dhcp relay information trusted ?

DHCP Snooping WLC

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