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Super Contributor II

Problem with DHCP Local L2

Hi experts,

 

I am trying to understand the DHCP scope Local L2 in Instant. I have built a lab which is made up of one IAP, one router and one firewall, as illustrated below:

dhcplocall2.png

The configuration of the IAP is as follow

dhcplocall2iap.PNG

When I connect my laptop to the WLAN Test, it gets an IP in the 172.16.2.0/24 subnet but it can't access the Internet, even I can't ping the gateway 10.10.10.1. What am I missing?

 

Regards,

Julián

 

Re: Problem with DHCP Local L2

Hey, did the IAP actually accept this configuration? My thoughts are that your client has an IP in the 172.16.2.x range but the clients default gateway is 10.10.10.1 which I expect wouldn't work? In Local L2 mode, the DHCP is completed by the IAP but the gateway would be hosted by another device in the same subnet e.g a core switch for the client vlan.

 

Are the VLAN's defined on 10.10.10.1 as well?


ACMA, ACMP, ACSA
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Super Contributor II

Re: Problem with DHCP Local L2

Hi zailon0,

 

Yes, you are right, although the IAP did accept the configuration. Then, you think if the segment between the IAP and the router is in the 172.16.2.0/24 subnet and the default gateway is 172.16.2.1 (the router interface) the scenario would work, don't you?

 

Regards,

Julian

Re: Problem with DHCP Local L2

Yes, providing the vlans are available and and the router is able to provide vlan routing

Sent from my iPhone

ACMA, ACMP, ACSA
If my post addresses your query, give kudos:)
Super Contributor II

Re: Problem with DHCP Local L2

Hi zailon0,

 

After changing the segment between the IAP and the router to subnet 172.16.2.0/24 and the default gateway to 172.16.2.1 (the router interface), the WLAN works. The only thing I don't understand is it works if the VLAN of the DHCP server is 1, but if the VLAN of the DHCP server is other than 1 (2, 3, ...) it doesn't work. The IAP is directly connected to the router interface. Do you know the reason?

 

Regards,

Julián

Super Contributor II

Re: Problem with DHCP Local L2

Hi zailon0,

 

Do you know the reason for what I explained above?

 

Many thanks,

Julián

Re: Problem with DHCP Local L2

Hey, sorry I was busy and unable to respond sooner. Is your router able to understand vlan tag's?


ACMA, ACMP, ACSA
If my post addresses your query, give kudos:)
Super Contributor II

Re: Problem with DHCP Local L2

Thanks man.

I think it is, because I have been able to test the DCHP Local and DHCP Local L3 with VLANs other than 1.

On the other hand, I wanted to exclude some addresses as show below

dhcplocall2_bis.png

but I don't understant the red message. It seems you only can exclude the entire address range, which makes no sense. If a try to exclude the addresses separately like this

dhcplocall2_bis2.png

I test and the client is not able to obtain IP address, again it seems the Instant exclude the entire address range. And also I don't understand the help message. Do you know anything about this or why the client can't get an IP address when I exclude these two IP addresses?

 

Regards,

Julián

Super Contributor II

Re: Problem with DHCP Local L2

Hi zailon0,

 

Were you able to check my last message?

 

Regards,

Julián

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