Dashboard and API inconsistent in updating new Client IP address?

[Steve_H]

We are using RADIUS CoA with the new bounce-host-port support to set client VLANs on MS switches.

The client device successfully gets a new IP address in the newly assigned VLAN reliably and quickly.

The challenge I have is getting visibility of this newly assigned client IP address from the API.

Note:

* we've disabled RADIUS accounting because it will either have no framed-ip-address on the initial accept, or will have the old IP address if we trigger an accounting update via a vlan change (cisco switches have aaa accounting delay-start to address this problem), so RADIUS accounting isn't useful for this scenario.

* syslog for MX dhcp events isn't useful because it will only send an event on a new lease, so if I move the client to a VLAN where it's had an IP address, no dhcp event is generated.

If I change the client IP address, it can take between 60sec and 4mins for an update to Dashboard.

Sometimes Dashboard doesn't update for 20+ minutes. 

If I look at the API:  https://dashboard.meraki.com/api/v0/networks/{networkID}/clients    - I may get the old address.

If I look at the API: https://api.meraki.com/api/v0/devices/{orgId}/clients?timespan=120  - I may get the new address (typically within 60-90 seconds).

I've opened a case with Meraki support to see if I can find out how this client-IP update process happens and try and understand why there are multiple places where this IP can be found and they're not consistently updated.

Does anyone have another way to reliably get the client IP address (local MX dhcp server so can't see this traffic via SPAN) - or has anyone else seen this issue?

Will update when I hear from support.

Thanks,
Steve

[jdsilva]

Are you a Windows shop?

Could you maybe use the DNS registration function of the Windows DHCP client to get this info from your DNS server(s)? If a client gets a new IP, and they are configured to register their DNS, then you should be able to get their new IP by resolving their hostname. 

[Steve_H]

Thanks jdsilva, not all clients are Windows and we can't use DNS for this. Trying to understand why there is such variability between different API calls that retrieve the client IP address and also trying to understand the process timers for collection of this info. 

e.g. the MS switch detects the client IP within X secs (immediately? assume it's via dhcp snooping but not sure)

MS switch updates internal tables after X seconds (ie, radius accounting only returns the correct client IP after several minutes)

MS switch updates Meraki cloud database every XX seconds

Dashboard updates from database every XX seconds

API - network - clients updates every XX seconds

API - org - clients updates every XX seconds

Thanks

Steve