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Cisco Bug: CSCvs42498 - NAT Alias not created for some configuration when using application redundancy

Last Modified

Aug 29, 2020

Products (8)

  • Cisco IOS
  • Cisco 4221 Integrated Services Router
  • Cisco 4431 Integrated Services Router
  • Cisco 4321 Integrated Services Router
  • Cisco 4331 Integrated Services Router
  • Cisco 4451-X Integrated Services Router
  • Cisco 4351 Integrated Services Router
  • Cisco Cloud Services Router 1000V

Known Affected Releases

16.6.6 16.9.5

Description (partial)

A pair of IOS-XE routers are configured for application redundancy with NAT. When the primary device is failed to the secondary device, the NAT table entries are properly synchronized. When the original primary again resumes the active role, an IP alias does not get created. The device connected on the outside interface will be unable to resolve arp for the inside global address and connectivity will fail.

The inside NAT configuration is using a pool of inside global addresses, which is part of the outside interface subnet. This configuration relies on ARP to complete for any device attached to the outside interface when trying to send traffic to the inside global address.
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