Use Management/KVM ip addresses in several UCS domains

[itm.i11.team]

Hello,

we run several UCS blade servers in two UCS domains. In every domain we have configured an ext-mgmt IP pool for access to the CIMC of the blades. As our both infrastructures are growing, I was wondering if we could use the IP addresses we use for the pools in both domains?

I have read the management guide (http://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/ucs-manager/GUI-User-Guides/Admin-Management/3-1/b_Cisco_UCS_Admin_Mgmt_Guide_3_1/b_Cisco_UCS_Admin_Mgmt_Guide_3_1_chapter_01101.html) and as far as I understand it, if we use inband IPv4 addresses these addresses are only used between the fabric interconnects and the blade servers?

Therefore I could not address the KVM from "outside" though via the UCS Manager (Equipment -> Chassis -> Server -> Actions "KVM Console"). Am I correct? I did some testing though did not manage to start KVM without our current configuration (ext-mgmt IP pool providing Outband IPv4 addresses for every single server).

Thanks in advance!

Regards

 Martin

[Walter Dey]

Hi Martin

Talking about out of band (ext-mgmt IP pool): you are aware, that this pool has to be in the same IP subnet / vlan as the IP address of the fabric interconnects mgt interfaces (and VIP).

Therefore I would never share this pools, avoiding duplicate IP address issues !

You are most likely use private addresses anyway ? 

Walter.

[itm.i11.team]

Hi Walter,

yes those IPs are in the same subnet as the fabric interconnects and their VIP. We are also using private addresses.

These addresses are "only" used if we access the CIMC via KVM, right? So it would also help if there is a way to free some unused IPs. We only need KVM access during the installation of a server and perhaps later if there are any issues with the system.

Therefore an option to temporarily assign mgmt IPs when we need them would be a great thing.

 Martin

[Walter Dey · Accepted solution]

Hi Martin

I think this is not possible ! as soon as you insert a blade, it will take a IP address out of the ext-mgmt pool and assigns it to CIMC ! Therefore this IP address is allocated to a chassis / slot, meaning if you move the blade to another slot, most likely it will get another address. This is a challenge, if you want a DNS entry for a Blade / KVM access.

Walter.

[itm.i11.team]

Hi Walter,

thanks for the answer, I have done some testing and I also think that there is no way at the moment. Therefore I am trying to shrink my IP pools which leads me to the next question: what is the best way to achieve this?

I've got a pool with addresse from x.x.x.20 to x.x.x.60 in which only the numbers x.x.x.50 to x.x.x.60 are used. At the moment I see no option to shink the pool and "extract" number .20 to .49 from the pool.

What happens when I delete the IP pool with assigned IPs in it?

EDIT: I could also test this in our testing environment: I added a new IP pool with sufficient IPs for the already assigned IPs. After deleting the old pool, the UCSM automatically assigned new IPs from the new pool after a few seconds.

So this works for me as I will shift the IPs between different pools and therefore shrink the pool.

 Martin

[Walter Dey]

Hi Martin

You can indeed delete this IP pool without Problems (CIMC will just have temporarily no IP address);

Then you create a new pool, and the blades CIMC will automatically get an IP address.

Please don't Forget to choose "sequential selection" in the pool definition.

Walter.