DHCP Question

[drswimmer]

Hello, 

I am looking for some guidance on configuration. The scenario is as follows:

I have one MX95 acting as our firewall, one MS425 acting as our layer 3 and a series of MS225's acting as layer 2 devices spread around our campus. The MS225's were practically given to me from Cisco due to production issues with my original purchase of  MS125's. My issue here is I have some non Meraki AP's that aren't carrying over the DHCP on a open wifi vlan. The MS425 is the DHCP server for this VLAN. The other VLANs that are also on these non Meraki AP's are working as intended. Yes the ports are trunked for these specific VLANs. On the port the ap is connected to all the way to the layer3.

When I assign myself a manual address on this public vlan while connected to the ap with the guest network, I am able to browse and etc. Packet captures are seeing my client device request dhcp, dhcp saying hey to my device... Then nothing. I'm not sure if I need some sort of IP helper or relay or something on the MS225's. If so, I'm not really sure how i go about doing that. Any help would be greatly appreciated. Thanks. 

[Ryan_Miles]

If your VLANs are extended from the 225s to the 425 there'd be no need for DHCP helpers anywhere. You should open a Support case so they can see the config and better assist you. 

[drswimmer]

I called them, sat on the phone for two hours while the engineer assigned to my case literally said "huh, that is weird". Gave me a couple things to try, which I have. Hence, I'd try here before calling again to see if I get a better engineer or something. 

[alemabrahao]

Who is your network's gateway? Is it the MS425? If it is not it, it is necessary to configure the DHCP relay, for example: If it is your MX, it is necessary to configure the MX to make the relay:

[drswimmer]

The MS425 is the gateway. Thanks for the information. 

[cmr]

What code release are you running on the switches?  Anything from 14.32 to 15.19 has some weird bugs related to ARP tables not populating correctly, some if you have deleted an SVI, some if you have created one and some just happen.  We have moved one site that kept having issues to 15.20 and so far, so good.  It has only been 6 days though, so I will wait a little longer before being sure this is the fix.

[drswimmer]

One of the things the Meraki engineer had me do is jump all of my switches from 14.x to 15.20. Still experiencing issue.

[alemabrahao]

I think you are missing some configuration.

[Ryan_Miles]

I think I might have found your Support case. What VLAN specifically are you having DHCP problems on? If I'm looking at the correct dashboard I see 22 interfaces on the MS425 and 22 interfaces on the MX95. Which I also don't understand. Is the 425 is the L3 gateway there should only then be a transit VLAN to the MX. I see pretty much all the same VLANs/subnets on both the switch and MX?

[drswimmer]

The 425 is supposed to be the L3 gateway, but honestly some of the existing settings are carry over from the former MX100 and a Dell layer L3 that I didn't want to stir the pot too much. And it sounds like you did indeed find my case. The VLAN in question is 2.

[Ryan_Miles · Accepted solution]

I see you've now moved VLAN L3 interface from the MS425 to the MX95. I see 25 DHCP leases handed out from the MX95. I see the subnet was also changed.

So, is this resolved now?

[drswimmer]

Seems to be working now. Not what I would have liked, but it's working. Also going to be removing all the vlans from the MX and creating the transit vlan between the MX and MS from reading the documentation. Thanks.