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Configuring PATing on more than one router interface

haithamnofal
Level 3
Level 3

Hi,

Can I configure PATing using the keyword "overload" on more than one router interface; when trying to configure more than one NAT rule using the keyword "overload" it gives an error that dynamics NATing is already in use.

Regards,

Haitham

5 Replies 5

dradhika
Cisco Employee
Cisco Employee

Hi Haitham,

Yes you can use it on more than one interface.

'dynamics NATing is already in use' is unsually given when you are trying to change a rule from which the ip address is already in use.

Were you trying to give a different interface for the same access list?

Normally for one access-list you can use only a single interface.

Let me know if you were trying something different.

Thanks,

Radhika

Hi Radhika,

What I meant will be clearer when I give this senario and then let me know if what you mentioned in your post is applicable here or not:

interface FastEthernet0/0

ip address *.*.*.*

ip nat outside

duplex auto

speed auto

interface FastEthernet0/1

ip address *.*.*.*

ip nat outside

duplex auto

speed auto

interface FastEthernet0/2

ip address *.*.*.*

ip nat inside

duplex auto

speed auto

access-list 1 permit any

ip nat inside source list 1 interface FastEthernet0/0 overload

Now, when I try to enter the command:

ip nat inside source list 1 interface FastEthernet0/1 overload

I receive an error reading that dynamic NAT is already in use. I need to have dynamic NAT enabled on both fa0/0 and 0/1 because I am load balancing between the 2 link. Can you please clarify your point in your previous post based on my scenario?

Thanks,

Haitham

http://www.cisco.com/warp/public/556/12.html

I don't think you can have 2 separate instances of NAT overload, but you can define the pool to include more then one interface. (see the example in the above document)

I think you may be trying to accomplish this:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t15/ft_glbp.htm

Hi Haitham,

I can think of the following solution.

Try creating two extended access-lists,

Access-list one includes networks from f0/2 to f0/0 and access-list two includes networks from f0/2 to f0/1

now you can create two dynamic rules,

ip nat inside source list one interface f0/0 overload

ip nat inside source list two interface f0/1 overload

Now when the traffic goes through f0/0 its ip address will be used and when the traffic goes from f0/1 its ip address will be used.

Hope this helps,

Radhika

Amit Singh
Cisco Employee
Cisco Employee

I agree with Radhika on this. You can also achieve the same using the route maps along with NAT config.

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080093fca.shtml

HTH,

-amit singh

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