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New Member

BGP down when we do NAT

nternet facing router is having a bgp peering with the ISP. When we do a static nat for one of the LAN IP and overload it with outside interface the BGP session is becoming active.


I have shared the configuration and sh ver along with this



HelloCan you show your config


Can you show your config?




Please don't forget to rate any posts that have been helpful. Thanks.

Could be following IOS bug

Could be following IOS bug -


Please post the show version as well.



New Member

Hi, I dont think it is



I dont think it is related to this bug. I am running an IOS where the bug is fixed. 

Hi, I would like to test this



I would like to test this case. Can you share the following outputs, my e-mail id is -


show tech

show ip bgp summary

show ip bgp neighbors

debug ip bgp

debug ip nat detailed

And the NAT Configuration that you apply on the router?



New Member

R1!interface GigabitEthernet0

interface GigabitEthernet0/0/1(connected to ISP)
ip nat outside
int GigabitEthernet0/0/0 (connected to LAN switch)
ip nat inside
ip nat inside source static interface gigabitEthernet 0/0/1
router bgp 133
 bgp log-neighbor-changes
 network mask
 neighbor remote-as 4755

R1 uptime is 11 weeks, 5 days, 20 hours, 1 minute
Uptime for this control processor is 11 weeks, 5 days, 20 hours, 2 minutes
System returned to ROM by reload
System image file is "bootflash:asr1001-universalk9.03.04.06.S.151-3.S6.bin"
Last reload reason: PowerOn




HelloCan you explain your lan


Can you explain your lan ip addressing, why are you natting on this address range and then advertising it - Is this an ip range you just selected  or was it supplied to you?

Is this bgp peering towards your ISP?




Please don't forget to rate any posts that have been helpful. Thanks.
New Member

 I want to NAT for only one


I want to NAT for only one or 2 users, hence using this IP range. 


Yes this BGP peering is towards the ISP. 


Hi , I have two question

Hi ,


I have two question after seeing your configuration

1) If is your inside network and your trying to hide to external world by nating to gig interface IP address, then why are you advertising it and to whom your advertising.

2) static nat is one to one nat. if you are nating server/host statically with interface,dont overload with interface it doesn't work.


When you do static nat with interface IP ,whenever there is any request come for router interface IP will redirected to nated IP so that's why services like telnet ,ping will be send to NATed IP address .In your case ,when there is request coming to your physical IP address ,router is looking for nat statement and sending to thats why your BGP neighborship is not working.




New Member

There are few sites which

There are few sites which allows access to only the IP of the ISP.

The range we are using is not registered in APNIC, but somewhere else in US, hence the access is denied.


We are trying to NAT to provide access to those sites.

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