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Cisco Bug: CSCus55505 - ASRNAT: Static PAT commands are lost from the config after reboot

Last Modified

Mar 15, 2018

Products (1)

  • Cisco ASR 1000 Series Aggregation Services Routers

Known Affected Releases

15.5(1)S

Description (partial)

Symptom:
It is possible to configure static PAT to router interface (or interface IP) and dynamic PAT to router interface (or interface IP) at the same time. This is a valid and supported configuration used by many customers which have single public IP address. Example:

ip nat inside source static tcp 10.1.75.2 23 interface GigabitEthernet0/0/1.99 5000
ip nat inside source list 100 interface GigabitEthernet0/0/1.99 overload

In this case, static PAT command will be lost after router reload, because we put commands into the running-config and startup-config in reverse order. Dynamic PAT command is processed first during bootup, NAT allocates dynamic TCP portblock 4096 - 5119 for dynamic PAT and static PAT command is rejected, because TCP/5000 is within the 4096 - 5119 range.

So, the requirement is: we need to place static NAT/PAT commands into configuration before dynamic NAT/PAT commands and process them first after reboot.

Conditions:
IOS-XE versions have this defect.
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