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looping when traceroute

Level 1
Level 1

        Hi All,

I have dynamic nat on the router

ip nat pool route  202.15.16..224  netmask

ip nat inside source list 166 pool route overload.

ip route 202.15.16.x

with above config everthing works fine.when i  excute show ip nat translations i get correct output.

when i do traceroute from outside network to

output reaches to first isp router as 202.15.16.X than to and agin to 202.15.16.x this looping goes on to 30 hops.

Can i know why this is happening .But i am able to  access the internet, everything works fine.

5 Replies 5

Raju Sekharan
Cisco Employee
Cisco Employee

You are using dynamic nat. Nating will happen only from inside interface to outside interface. Also it will allow the reply packets for packets originated from inside

If you ping from outside to inside, it won't work.

if you need outside to inside access, you need to configure static nat

It is looping becasue your default route is pointing back to 202.15.16.X


** rate if the post helps***

Hi rajs2

Thanks for explanation.

The thing is  isp has provided ip .I have already configured static nat for some servers . and for lan range i have carried out dynamic pat.

I have to point out route to 202.15.16.x as it is isp end.

So there any way to prevent this,Thus it have any effect on the traffic.(loops)

There is no issue with this. Only if someone tries to reach a non-used IP, this will happen

Hi Prashant,

Raj is correct whenever you will do ping to any ip of pool it will reach to the destination with any you are pinging to one of ISP IP it is going back to natted ip that is other end of ISP it is getting looped but I dont think u will face the same issue while doing a ping or trace to pool ip.

Leave it as it is not going to affect ur traffic or not lead to any issue.


Pls rate helpful info.    

Thanks amit and rajs2

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