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New Member

CSS-11503 redundancy

Does anyone know if one can use a non-dedicated interface (i.e. one through which other traffic flows) for redundancy? I ask this as the pair of 11503's in question will only have the two gig interfaces available, both of their slots filled with SSL accelerators.

The documentation states that one must use a dedicated interface for redundancy, unfortunately with only 2 interfaces on an 11503 we don't have many choices....

New Member

Re: CSS-11503 redundancy

You can depending upon your network topology. We have recently completed a successful deployment of redundant 11503's with two GE interfaces, connected to Catalyst 6513's at the core. At the recommendation of our Cisco SE, we have architected a simple box-to-box redundancy configuration using a dedicated circuit VLAN on the CSS for app session redundancy. We've tested this under significant traffic loads and it performs brilliantly. If you're interested, email me directly at and we can discuss further. Best regards.

New Member

Re: CSS-11503 redundancy

Does anyone know if this is this a "TAC supported" configuration? We're looking at doing the same setup.


Cisco Employee

Re: CSS-11503 redundancy

This is actually not recommended and not supported by the TAC.



Re: CSS-11503 redundancy


Only a direct Connection between the CSSes is supported compare to the Usage Guidelines in

I'm havin more or less the same problem as I've a customer with 2 locations and the use ISC would help a lot. My only possibility to solve this is a DWDM link between those 2 locations but that's quite an expensive solution. Maybe the possibility of a using a VLAN (L2 infrastructure) for ISC like the FT-VLAN at the CSM would be great idea for the future...

Kind Regards


New Member

Re: CSS-11503 redundancy

I am not sure this will be much help but we have pairs of 11503's with just 2 gig interfaces and have them configured as one-armed configurations.

This gives the user VLAN on one Gig interface and frees the second for the redundancy interface.

Not much use if you need to position the CSS as a boundary/barrier point in the physical configuration, or if your backend servers cannot tolerate the Source addres NAT that the one-armed config requires..... but great if you do not need these.

Good luck

Andrew T

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