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I would like to do NAT while load sharing is active on R1 and R2 (cisco routers). Do you have any ideas how should I do it effectively? Is there some way to share a common NAT table between the 2 routers?

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    NAT cannot handle asymmetric routing. You will need to make sure that any flow only uses one of the routers, not both. A NAT table is not shared between the routers.
    – Ron Maupin
    May 24, 2019 at 15:09
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Dec 15, 2019 at 3:32

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In that scenario, the load-balancing decision needs to be done before branching to either router - within the core switch or between R1/R2 and the core switch. Also, there's no way to share a NAT table between routers, especially when their public IPs differ.

A more viable scenario is to connect both WAN links to each router and run the routers in a fail-over setup (e.g. VRRP or HSRP). Then you can load balance the L4 sessions based on source IP (range), destination IP (range), protocol, current link load, ... - depending on the router capabilities.

Load balancing within each L4 session isn't possible.

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Ether channel will solve your problem.

Following load balancing options are available in a switch.

  • dst-ip— Load sharing is based on the destination-host IP address.
  • dst-mac— based on the destination-host MAC address of the incoming packet.
  • src-dst-ip— based on the source-and-destination host-IP address.
  • src-dst-mac—based on the source-and-destination host-MAC address.
  • src-ip— based on the source-host IP address.
  • src-mac— is based on the source-MAC address of the incoming packet. Additionally you can try with FHRP protocols as well

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