Loss of a CX4 module in an IRF stack: the master switch works, the switch become master not working

[LLarouanne]

Hello,
I need to know if it is possible to ensure that all elements forming IRF stack continue to have access to network resources when IRF stack is separated.

Here is my architecture:
- I have two core network 10504 chassis IRF.
- Switch to access: several stacks of 5120 (still IRF) consisting of 3 or 4 switches. These stacks are formed via a CX4 module in slot 1 of each switch. The # 2 slot was taken by the module 2-port 10 Gigabit.
- Switch "server": 5900 stacks consisting of two switches.

Each cell is connected to the core network by means of an aggregate of two 10-Gigabit ports.
My core network is configured to use LACP MAD-bearing function to a loss of IRF link between the two frame.

My problem:
If I simulate a failed CX4 module on one of my piles of 5120, my stack is then separated into two. Initially switch Master, Master remains, and connected users always access networks over resources.

Initially Backup switch becomes Master, but the link to the related aggregate the switch to the core network is blocked by the LACP.
So I have quite a switch, or even 2 or 3, which no longer access the ressouces networks in case of failure of a CX4 module.

My question is: is there a way that all the switches of the IRF stack access to network resources in the event of failure of a CX4 module. 

PS: I made a model with the spanning-tree: it works but I lose everything in advance of the aggregate: what does not suit me.

If you find me a solution, I would be grateful.

Laetitia.

[Ian Vaughan]

Howdy,
The IRF is designed to "fail safe" - you are not supposed to have two nodes on yuor network with duplicate IP addresses and bridge ID's therefore the non-master half gets all the access ports shut-off by the MAD process.
If you want a fully resilient design you need to supplement your CX4 modules. Can you add DAC cables for local stacking in the second "spare" port of the SFP+ 10Gb module?
Any 10Gb physical port should be able to be added to the configuration as an IRF port.
HTH
Ian

[LLarouanne]

the solution of the DAC-cable Resolve my problem completely. This is beast but I had not thought of.

Thank you.