Question about the operation of NAT

[wajahat]

Hi all, NAT is used to convert local ip addresses to global ip addresses.
This means that session can be started from the local host.Any host outside the local network cannot start the session.
In rfc 3022 there is a clause that in some cases the external host can also initiate the session.

How ?

Any detail in this regard would be helpful.
Thanks
wajahat

 

[oz]

Re: NAT???

Hi,
When NATing is activated in a router, an entry is created in the NAT table containing local and remote IP adresses and "virtual ports". When this router receives something from the public network, the source public IP is replaced by its own IP address and the source port by a port from a range of "virtual port Ids" managed by the router.

From the network side, the remote host / network element responds with a set of datagrams containing the router IP address (destination address) and "virtual port" defined by the router.

As such, NATing can be initiated by any element in the network as long as it supports this functionality.