03-14-2019 09:43 AM
I am facing issue when i configured Ip dhcp snooping comman in c2960x ,3750 & 3650...
Issue : users/clients do not receive Ip address automatically after configuring the ipIdhcp snooping command.
Do you have any idea about this?
Kind regards,
Mahendra Gharbude
03-14-2019 10:02 AM
We need to know what is the version of IOS you running, and show us your configuration.
do you have any debug logs, when they enable ip dhcp snoop.
03-14-2019 10:33 PM
03-14-2019 10:33 PM
Hi,
iOS version is 15.2(2)E7 ,model- 2960x
Configuration on switch- Ip dhcp snooping vlan 1- 999
Currently snooping is disabled on switch.
Attached screenshot.
03-14-2019 10:05 AM
Hi @GMahendra ,
Could you show us the settings you enter?
This tool is implemented to avoid attacks by fake DHCP services.
In addition, you must indicate which interfaces will be reliable, that is, by which interface if addresses can be received through DHCP.
Regards
03-14-2019 10:45 AM - edited 03-14-2019 06:09 PM
Hello
Disable option 82 insertion on the access layer switches where snooping is applied also trust the switches uplinks then test again
Sh ip dhcp snooping
No ip dhcp snooping information option
03-14-2019 09:28 PM
Thanks Paul,
If I remove option 82 ,what will be impact in network. How is option 82 works?
What is command to enable the option 82 again in network.
Kind regards,
Mahendra
03-15-2019 03:15 AM
Hello
Its only applicable when dhcp snooping is enabled and as you have reported that some of your clients are not able to receive dhcp allocated after snooping is activated so the suggestion would be to try and disable option 82 on switches (3560's.3650's) that by default this feature on when snooping applied.
You can reapply it by simply - ip dhcp snooping information option
Please review this document - it will explain a lot clear then i ever can
03-15-2019 09:13 AM
Thanks Paul. I will try it and let you know.
03-14-2019 11:19 AM
Adding something else, dont forget to define and insert the command under the trusted interface that can able transport dhcp packets.
ip dhcp snooping trust
check it for more information: https://www.cisco.com/c/en/us/support/docs/smb/switches/cisco-small-business-300-series-managed-switches/smb5715-configure-dhcp-trusted-interface-settings-on-a-switch-throug.html
03-15-2019 11:27 AM
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