That is correct Pieter-Jan

 

Regards,

 

Tyson Scott - CCIE #13513 R&S, Security, and SP

Technical Instructor - IPexpert, Inc.

Mailto:  <mailto:[email protected]> [email protected]

Telephone: +1.810.326.1444, ext. 208

Live Assistance, Please visit:  <http://www.ipexpert.com/chat>
www.ipexpert.com/chat

eFax: +1.810.454.0130

 

IPexpert is a premier provider of Self-Study Workbooks, Video on Demand,
Audio Tools, Online Hardware Rental and Classroom Training for the Cisco
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From: [email protected]
[mailto:[email protected]] On Behalf Of Pieter-Jan
Nefkens
Sent: Wednesday, April 07, 2010 1:35 PM
To: Brandon Carroll
Cc: Kingsley Charles; [email protected]
Subject: Re: [OSL | CCIE_Security] NAT with overload

 

HI Brandon, Kings,

 

If I remember correctly, if you do not specify overload, the first ip that
is matched from the access-list is natted to the external address, leaving
the other potential devices being unable to access the network. When the
nat-timeout occurs, the global ip address becomes available again. It is
comparible with the global pool for nat, but then with just one ip-address.

 

E.g. nat is being applied.

When using the overload keyword, pat is being used.

 

 

You can compare it with the global command on the pix / asa.

If you specify global (outside) 1 ip1-ip2

than the first two devices accessing the network are being translated, the
third one basically has bad luck until one of the first nat entries time
out. Thats why I (almost) always configure a global (outside) 1 ip3 as well,
so that PAT is occuring as well.

 

Just a tip, if you don't know it yet.

 

If you do a command like

"ip nat inside source 123 int dialer1 overload"

remember to also put a 

"ip nat inside source static tcp <internalipofrouter> 22 int dialer1 22
extendable"

in it as well. Otherwise you won't be able to remotely login to your DSL
router/modem, as the dynamic nat would take presedence.

 

 

I think it could even a troubleshouting item in the lab as well..

 

HTH

PIeter-Jan

 

 

 

On 7 apr 2010, at 18:37, Brandon Carroll wrote:





Kings,  

 

I believe the IOS automatically overloads now if you don't specify.  Older
IOS you had to use the overload command.


Regards,

 

Brandon Carroll - CCIE #23837

Senior Technical Instructor - IPexpert

Mailto: [email protected]

Telephone: +1.810.326.1444

Live Assistance, Please visit: www.ipexpert.com/chat

eFax: +1.810.454.0130

 

IPexpert is a premier provider of Self-Study Workbooks, Video on Demand,
Audio Tools, Online Hardware Rental and Classroom Training for the Cisco
CCIE (R&S, Voice, Security & Service Provider) certification(s) with
training locations throughout the United States, Europe, South Asia and
Australia. Be sure to visit our online communities at
www.ipexpert.com/communities and our public website at www.ipexpert.com
<http://www.ipexpert.com/> 

 

 

 

On Apr 7, 2010, at 9:11 AM, Kingsley Charles wrote:





Hi Brandon

 

IOS accepts the following command without "overload" keyword. Isn't the
following PAT?

 

ip nat source list 123 interface g0/0

 

 

 

 

With regards

Kings

On Wed, Apr 7, 2010 at 9:38 PM, Brandon Carroll <[email protected]>
wrote:

Overload takes you from using NAT to using PAT.

Regards,

Brandon Carroll - CCIE #23837
Senior Technical Instructor - IPexpert
Mailto: [email protected]
Telephone: +1.810.326.1444
Live Assistance, Please visit: www.ipexpert.com/chat
eFax: +1.810.454.0130

IPexpert is a premier provider of Self-Study Workbooks, Video on Demand,
Audio Tools, Online Hardware Rental and Classroom Training for the Cisco
CCIE (R&S, Voice, Security & Service Provider) certification(s) with
training locations throughout the United States, Europe, South Asia and
Australia. Be sure to visit our online communities at
www.ipexpert.com/communities and our public website at www.ipexpert.com
<http://www.ipexpert.com/> 




On Apr 7, 2010, at 9:06 AM, Kingsley Charles wrote:

> Hi all
>
> When we configure as following, all addresses matching 123 will be
translated to g0/0 and that is PAT. Port numbers are used to distinguish
each hosts.
>
> ip nat source list 123 interface g0/0
>
>
> What  does overload do?
>
>
> router1(config)#ip nat source list 123 interface g0/0 ?
>   overload  Overload an address translation
>   vrf       Specify vrf
>   <cr>
>
> router1(config)#ip nat source list 123 pool addr ?
>   overload  Overload an address translation
>   vrf       Specify vrf
>   <cr>
>
>
> With regards
> Kigs
>

> _______________________________________________
> For more information regarding industry leading CCIE Lab training, please
visit www.ipexpert.com <http://www.ipexpert.com/> 

 

 

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