DHCP reservation in Meraki switch stack

[SrandaZitra]

Hi all, 

I work in a shop where it's usual to configure DHCP pools for switches. A colleague to mine struggles with configuring DHCP reservation for Meraki Switch Stack - is that practically possible? 

It's impossible to configure the same IP address reservation for multiple MAC addresses (stack members).

Is there any floating MAC address that's held only by active switch in the stack (of course DHCP request would need to be made from that MAC)?

Thanks in advance for your hints

[alemabrahao]

Meraki switches work in a different way, where even when stacked, each switch must have its own IP. In other words, it is not possible to reserve the same IP for different switches.

[alemabrahao]

Just a note, this statement is not true for the MS390 ande C9300 models, it does not follow this rule.

[SrandaZitra]

Thank you for the response, would you be so kind and elaborate a bit more about MS390 and C9300 models - i.e. what is the difference in comparison to lower class switches, e.g. 210? Thanks! 

[cmr]

The MS390 /C9300-M switches are Cisco Catalyst hardware that run the Cisco IOS-XE operating system.  For stable and RC firmware, the Meraki management software runs in a container on top.  For the beta it is part of IOS-XE.

The other switches are Meraki native with no IOS at all.

[cmr]

Adding to what @alemabrahao said, the management interfaces of each switch have their own Ip addresses, these normally remain constant, regardless of which member is the active stack master.

[SrandaZitra]

Thank you. 

I should've write it in my original post - the switches in question are 9300. As @alemabrahao wrote, these are different in comparison to lower class switches - meaning 1 IP is assigned to the stack members. 

I am curious about the details - ie. I have one IP address assigned to all the switches - how do I configure DHCP reservations? It's not clear to me due to answer of @alemabrahao that would need to be slightly more elaborated. 

[alemabrahao · Accepted solution]

To be honest the documentation is not clear about it, so I suggest you open a support case.

https://documentation.meraki.com/MS/Stacking/Switch_Stacks

[SrandaZitra]

Thank you. I believe this is the closest to answering my question. I will conduct an experiment to figure it out empirically and get back to this topic. 

[SrandaZitra]

Aight, so my colleague that has the stack on his table (different site) has performed a test with following results: 

1. DHCP reservation was created for active (stack-master) stack member

2. Active stack member was forcibly disconnected from power

3. New switch became active

4. This resulted in lack of connectivity to Meraki cloud for 30 minutes

5. After 30 minutes, the stack sent DHCP request resulting in having random dhcp-pool address, connectivity with Meraki cloud was renewed

6. After re-connecting the switch disconnected in step #2 , that newly-booted switch acquired random dhcp-pool address which was changed to stack active switch' address soon after

7. After reload of the whole stack, it took whopping 30 minutes for the stack to become visible in Meraki portal

8. The switch that was originally active is active again and has DHCP-reservation address
   
   To me this seems that assigning the stack a static IP and calling it a day will be the best we can do. 

[cmr]

Did any of this (other than the whole stack reboot) affect client connectivity?

As a side note, the native IOS-XE comes online much faster, once that is ready for production you would have a significantly better experience.

[SrandaZitra]

The clients were able to communicate even though the stack was searching for IP address. 

[annmarie24us]

In my experience the best option is to reserve the IP address with the MAC address in the DHCP pool after the switch stack has acquired it DHCP address coming online to the Meraki Cloud.