Will the upgrade change my configuration or will I have to change this manually myself at some point?
It will be done automatically
What is the meaning of "Real IP" I am not sure what the means (reading up on it now)
It means that before 8.3 and higher versions when you created ACL's to allow traffic from outside to inside you always point the Natted IP address right? the global one....
Now beginning on 8.3 the whole concept changes and now we must point to the real IP address, the No-natted one.
- What else should I be concerned about during the upgrade?
Well, lot of things You are already aware of the memory, of some changes like the ACL stuff but remember that the entire NAT syntax also changes.
I would personally recommend you to avoid the 8.3 track. Go from the version you are currently now to an 8.4 version (the 8.3 is well known by having bugs)
Recommendations before the upgrade:
Disable the names feature
no names
Disable nat control if configured
no nat-control
Then u are good to go (make sure you have a configuration file saved of the version of 8.2 just in case you need to rollback)
Here is one document, Jounni (member of the CSC created) regarding nat
https://supportforums.cisco.com/docs/DOC-31116
This other is an 8.3 upgrade MUST know, make sure you read this
https://supportforums.cisco.com/docs/DOC-12690
Regards
Julio Carvajal
Senior Network Security and Core Specialist
CCIE #42930, 2xCCNP, JNCIP-SEC
