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ASR & Source Groups

I am a little confused with Portmapping and the advice on Source Groups in the documentation.

The section on "Configuring ASR" chapter 2 in the redundancy manual advises to Configure mutually exclusive port-map ranges on the redundant peers using the global-portmap command to avoid potential network port collisions.

However, we have a simple configuration that uses Source Groups to ensure that incoming requests to backend servers are Source NATted in a one-armed configuration. The content Rules and corresponding Services and Source Groups (with add DESTINATION service commands) are exactly replicated on each box.

The only differences in the configurations are the VLAN IP addresses for the redundant interfaces.

There is a single Virtual Router on a single redundnat interface on each box.

There is a separate ISC link between the two boxes.

Because the client request to backend servers are using Advanced Balance SSL, the backend server connection uses the delayed binding and a source port number is required.

When this conection is failed onto the "backup" router on the other box, I assume it will have to continue with the original source port number, otherwise the flow will break down.

Is this a correct interpretation and does it mean that there can be no conflict between the portmap ranges on the two boxes?

If so can I ignore this advice and leave the CSS to decide which port numbers to use?

Are there any implications with my configuration on the maximum number of flows that can be supported for a single rule with destination port defined and mapped to a different desination port on the backend servers?

Hope someone can advise ...... as it will save a lot of test setup and prooving!


Andrew T

Cisco Employee

Re: ASR & Source Groups

this restricion applies only if you are in the following condition :

"...if the master and backup CSSs have different ACL definitions .."

this is mentioned [not clearly] in the same documentation you referenced.