topic RE: when dhcp snooping entries removed ? in ExtremeSwitching (EXOS/Switch Engine)

when dhcp snooping entries removed ?

Burak_Kale — Thu, 07 May 2015 19:03:00 GMT

Hi ;

I know that we can clear dhcp-bindings for a port manually.

Are there any way to clear dhcp-bindings when an interface is down ?

Is there any way to create a timer for that or am i have to wait for the dhcp lease time?

Regards,

Burak.

RE: when dhcp snooping entries removed ?

Hernandez__Josh — Thu, 07 May 2015 19:08:00 GMT

Burak Kale,

If you are using an Extreme EXOS device you can use the following command to set the lease timer for DHCP:

configure vlan dhcp-lease-timer

If you want to clear the existing DHCP allocations use the following command:

clear vlan dhcp-address-allocation

RE: when dhcp snooping entries removed ?

Burak_Kale — Thu, 07 May 2015 19:14:00 GMT

Hi Joshua;

Thanks for the quick reply.

Is it same when we are using different dhcp server ?

Because i am just asking about dhcp snooping.

Regards,

Burak.

RE: when dhcp snooping entries removed ?

Hernandez__Josh — Thu, 07 May 2015 19:21:00 GMT

Burak,

What can you specify the role the Extreme device plays in the DHCP process?

RE: when dhcp snooping entries removed ?

Burak_Kale — Thu, 07 May 2015 19:38:00 GMT

We are using the dhcp snooping feature to ensure about DHCP security

Thanks

RE: when dhcp snooping entries removed ?

Hernandez__Josh — Thu, 07 May 2015 20:07:00 GMT

Burak,

Please explain in greater detail what you are wanting to accomplish.

RE: when dhcp snooping entries removed ?

Sumit_Tokle — Thu, 07 May 2015 20:55:00 GMT

if you are good at script then you can match the port down log and clear the snooping entry using the simple script

RE: when dhcp snooping entries removed ?

BrandonC — Thu, 07 May 2015 20:56:00 GMT

Hi Burak,

You can clear the DHCP snooping bindings for a vlan, but they cannot be cleared per-port. You could configure a UPM profile to clear the bindings on a link down, but since this would be per-vlan, it would not do what you are asking.

-Brandon

RE: when dhcp snooping entries removed ?

Burak_Kale — Thu, 07 May 2015 21:02:00 GMT

So i understand from that last two answers , we can do it by using a script file.

clear ip-security dhcp-snooping entries vlan "Default" ports 7

@Brandon ; we can clear the bindings using the following command .

I think if i can write correct script that finds the ports that goes down , i can do that.

Thanks for the ideas. I will try that , and if i succeed i will share.

Regards,

Burak.

RE: when dhcp snooping entries removed ?

BrandonC — Thu, 07 May 2015 21:11:00 GMT

Burak,

I apologize, I misspoke previously. You can specify the port in that command.

You should be able to find information on setting up UPM profiles in the Universal Port section of the EXOS User Guide.