Having trouble understanding Outside Local address

[zcc4123]

For the question above, I don't understand how 192.168.1.30 is the outside local address. Wouldn't the outside local address be 15.16.17.18 since that is the ip assigned to the host on the outside network?

I have been searching for the reasoning and have been getting 2 answers that are confusing me.

One where it goes 
Inside local - Outside local  -- Inside global - outside global  (1st pic)
and one 
Inside local - Inside global --  outside global - outside local   (2nd pic)

Can you explain to me if there's a difference or if i'm misinterpreting it.
Thanks!

 

[M02@rt37 · Accepted solution]

Hello @zcc4123 

First, by definiton, outside Local is the private IP assigned to an external device from the perspective of the inside network.

source: CCNP-ENCOR-350-401

The outside local address is how the external host (HostB) appears from the perspective of the internal network. In NAT, when an internal host accesses an external server, the external IP might be mapped to another local IP that the router recognizes. In this case, 192.168.1.30 is the outside local address because RouterA translates the outside host’s real IP (15.16.17.18) to a local representation inside the private network.

15.16.17.18 is the outside global address, which is the actual public IP of the external device. The question specifically asks for 'outisde local' , meaning how the external device is seen from within the private network.

[paul driver]

Hello

Local addressing =  Seen by devices on the inside
Inside Local (IL) = inside host addressing hidden and not advertised to the outside
Outside Local (OL) = outside side host addressing seen by inside hosts

Global  addressing = Seen by devices on the outside
Inside Global (IG) = inside hosts addressing seen by outside hosts
Outside Global (OG) = outside host addressing hidden and not known to the inside

[Giuseppe Larosa]

Hello @zcc4123 ,

just to add in this network scenario as we can see from the picture and from the details about source and destination IP addresses on the inside and the outside of the network the router is performing NAT not only from inside to outside that is called source NAT or SNAT it is also presenting the external server with a private IP address 192.168.1.30 and this is actually the Outside Local. So from outside to inside the router is also NATTing the destination address.

For this reason the show ip nat translations output reports 4 columns

Inside local Outside Local Inslde Global Outside Global

in standard scenarios where the router performs only SNAT from inside to outside Outside Local = Outside Global = public IP address but not in the scenario of the question

Hope to help

Giuseppe