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ACL issue

libra_ali786
Level 1
Level 1

I have a small issue with ACL.

My local network are 10.2.1.0/24 and 10.2.2/24 , When i apply indise local NAT like below. It translate my 10.2.1.0/24 and 10.2.2/24 network sucessfuly.


ip access-list standard Nat_Traffic

permit 10.1.0.0 0.0.255.255

permit 10.2.0.0 0.0.255.255

 

As per my understanding NAT traffic  should be rejected because my network fall in different subnet.

Please correct me why my local network translated with that above NAT?

Please explain with small example,

Thanks

 

1 Accepted Solution

Accepted Solutions

The subnet 10.2.0.0 /16 covers the IP range 10.2.0.0 - 10.2.255.255  , so within that range are your two /24's, each with the corresponding range:

10.2.1.0/24 = 10.2.1.0 - 10.2.1.255

10.2.2.0/24 = 10.2.2.0 - 10.2.2.255

 

 

...have a play around with http://www.subnet-calculator.com/ . If you are not familiar with IP subneting there are numerous online tutorials:

https://www.computernetworkingnotes.com/ccna-study-guide/subnetting-tutorial-subnetting-explained-with-examples.html

 

cheers,

Seb.

View solution in original post

3 Replies 3

Seb Rupik
VIP Alumni
VIP Alumni

Hi there,

This router NAT statement, so the ACL will use wildcard netmasks.

 

The ACE which matches your two local subnets is:

permit 10.2.0.0 0.0.255.255

 

...this is equivalent to 10.2.0.0/16 , which your two subnets are matched under.

 

cheers,

Seb.

 

but my subnet mask are different 10.2.0.0/24. What about the subnetmask?

Please suggest any link which i learn and clear my doubt.

The subnet 10.2.0.0 /16 covers the IP range 10.2.0.0 - 10.2.255.255  , so within that range are your two /24's, each with the corresponding range:

10.2.1.0/24 = 10.2.1.0 - 10.2.1.255

10.2.2.0/24 = 10.2.2.0 - 10.2.2.255

 

 

...have a play around with http://www.subnet-calculator.com/ . If you are not familiar with IP subneting there are numerous online tutorials:

https://www.computernetworkingnotes.com/ccna-study-guide/subnetting-tutorial-subnetting-explained-with-examples.html

 

cheers,

Seb.

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