%NAT: System busy. Try later

Unanswered Question
Jul 3rd, 2008
User Badges:
  • Silver, 250 points or more


Everytime I do a show run, wr mem or try to add a NAT statement, I get %NAT: System busy. Try later. I did the following but no luck:

%NAT: System busy. Try later

The %NAT: System busy. Try later error message appears when a show command related to NAT or a show running-config or write memory command is executed. This issue is due to the increase in the size of the NAT table. When the size of the NAT table increases, the router runs out of memory.

Reload the router in order to solve this issue. If the error message appears when HSRP SNAT is configured, configure these commands in order to resolve the issue:

Router(config)#standby delay minimum 20 reload 20

Router(config)#standby 2 preempt delay minimum 20 reload 20 sync 10

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Steve Lyons Sat, 07/05/2008 - 06:40
User Badges:
  • Cisco Employee,

It appears you are running out of memory when using NAT. You could try lowering your nat timeouts and see if problem clears up. I would recommend opening a TAC case and have TAC review your configuration.

Tshi M Thu, 07/10/2008 - 12:32
User Badges:
  • Silver, 250 points or more

Thanks. I cleared the NAT table and reloaded teh routers since my last posting. I have yet to see the same problem. If it does come back, I will open a TAC case.


purohit_810 Thu, 07/10/2008 - 15:39
User Badges:
  • Silver, 250 points or more

1) Can you see how much memory available free?

2) If memory is available free more

than 12MB, it is not momory problem. - It is an IOS problem.

3) How much traffic pass by each NAT statement?

4)Observe by show NAT statement.

5) Do free memory by deleting older IOS or unecessary configuration.

See this could helps you...


Dharmesh Purohit

purohit_810 Thu, 07/10/2008 - 15:40
User Badges:
  • Silver, 250 points or more

Here is one caveats:


Symptoms: When you enter a show command that is related to NAT or you enter the show run command when there is a NAT configuration, the "%NAT: System busy. Try later" error message may be generated. In addition, "%SYS-2-NOBLOCK" messages may be generated and the CPU utilization may be very high in the IP Input process.

Conditions: These symptoms are observed on a Cisco 1750 that runs Cisco IOS Release 12.3(9) and that is configured for NAT with SIP traffic (the router is a gateway for IP phones).

Workaround: Reload the router.


Dharmesh Purohit


This Discussion