Is Stateful-NAT embedded with HSRP? Can it be implemented with IP-SLA?

[ps12]

Is Stateful-NAT embedded with HSRP? Is there no way that Stateful-NAT can be implemented stand-alone or with IP-SLA? 

[AndreaTornaghi]

Dear,

I think that you can use Stateful-NAT only with HSRP.

From my point of view IP SLA has a different scope, ex. you can monitor a destination ip via icmp and check if it is reachable and associate this ip sla to a track on a ip route. 

"The Scalability for Stateful NAT feature allows Stateful Network Address Translation (SNAT) to control the Hot Standby Router Protocol (HSRP) state change until the NAT information is completely exchanged. The ability to change the default TCP mode to User Datagram Protocol (UDP) mode, and the ability to disable asymmetric queuing have been added. When UDP mode is used, SNAT will send messages over UDP mode using a proprietary acknowledgement/retransmit mechanism."

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/12-4t/nat-12-4t-book/iadnat-scalability-stateful.html

[ps12]

In my scenario, I want to have redundancy between R1-R2 [active] and R2-R3 [backup] path. I cannot implement HSRP because I do not have a switch, hence, for redundancy, I am using IP-SLA. 

Now I want all traffic leaving from R1 to be NAT-ed, and NAT should be stateful [to be shared with R3]. How do you suggest I implement that?  

[AndreaTornaghi]

Have you configured IP SLA on your layer 3 switch?

You have three routers, but I'm not understanding which role has R2 in your topology. It has three interfaces, one towards SW and others two towards  R1 and R3.  So it's a point of failure in your topology but it's not very clear which is its function.

However if R1, R2, R3 are sharing the same subnet towards the switch, so they are connected on the same vlan on switch you can configure HSRP on routers.

[ps12]

No, the L3 Switch does not have IP-SLA configured on it. My L3 Switch has some networks configured on it which need to reach to the networks beyond R1 and R3. All the routes from L3 Switch need to pass through R2 only and from R2 these networks take R1 path. R3 works as a backup. When networks are leaving from R1 they need to be NAT-ed.   

The link connecting R1-L3 S/W and R3-L3 S/W currently aren't participating. They have a different purpose, part of a vrf.  

[AndreaTornaghi]

Have you configured IP SLA on your layer 3 switch?

You have three routers, but I'm not understanding which role has R2 in your topology. It has three interfaces, one towards SW and others two towards  R1 and R3.  So it's a point of failure in your topology but it's not very clear which is its function.

However if R1, R2, R3 are sharing the same subnet towards the switch, so they are connected on the same vlan on switch you can configure HSRP on routers.