Cisco Systems Dynamic Outside NAT

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Subject Author Date
Dynamic Outside NAT Darren Green 11-30-05
Posted by Darren Green on November 30, 2005, 4:43 pm
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Hi,

Any help on this would be appreciated.

If I want to implement dynamic outside NAT but my 2 x outside sites have
the same IP ranges is there a workaround.

                                        --------Site 1 ---192.168.1.X
Central Site (inside)----PIX---(outside)
say 10.1.0.1 /24                        --------Site 2 ---192.168.1.X

I have seen examples where outside NAT allows me to translate address to
a suitable address range on the inside. But what happens if the 2 x
remote sites have the same IP's ranges (NB The above remote IP ranges
belong to different companies).

Can't see an expample on Cisco.com but still searching.

How could I distinguish between the 2.

Regards

Darren

Posted by mcaissie on November 30, 2005, 5:47 pm
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Assuming you want to establish a VPN with both sites,
You can always do double policy NATing.
I got it to work in lab, but didn't go further. There is
the problem that each site sees the central inside subnet with
different IPs, wich was a problem in my case.



Central Site translation
access-list Site1 permit ip [Central Inside real subnet] [Site1 translated
subnet]
access-list Site2 permit ip [Central Inside real subnet] [Site2 translated
subnet]
static (inside,outside) [Central translated subnet for site1] access-list
Site1 0 0
static (inside,outside) [Central translated subnet for site2] access-list
Site2 0 0


Sites translations
access-list b-Site1 permit ip [Site1 Real subnet] [Central translated subnet
for site1]
access-list b-Site2 permit ip [Site2 Real subnet] [Central translated subnet
for site2]
static (outside,inside) [Site1 translated subnet] access-list b-Site1 0 0
static (outside,inside) [Site2 translated subnet] access-list b-Site2 0 0


Crypto ACLs
access-list Map1 permit ip [Central translated subnet for site1] [Site1 Real
subnet]
access-list Map2 permit ip [Central translated subnet for site2] [Site2 Real
subnet]


crypto map xxxxx 10 ipsec-isakmp
crypto map xxxxx 10 match address Map1
crypto map xxxxx 10 set peer x.x.x.x
crypto map xxxxx 10 set transform-set xxxxxx
crypto map xxxxx 11 ipsec-isakmp
crypto map xxxxx 11 match address Map2
crypto map xxxxx 11 set peer x.x.x.x
crypto map xxxxx 11 set transform-set xxxxxx
crypto map xxxxx interface outside

This way when the central calls a site using the Site's translated
address, the site will see the
packet coming from the central translated addresses for this specific site.

This way you can have crypto maps that are mirror image, without any IP
conflicts.

But as you may saw in my other post "VRF aware IPSEC" , i am investigating
others ways to
resolve those kind of issus.



> Hi,
>
> Any help on this would be appreciated.
>
> If I want to implement dynamic outside NAT but my 2 x outside sites have
> the same IP ranges is there a workaround.
>
> --------Site 1 ---192.168.1.X
> Central Site (inside)----PIX---(outside)
> say 10.1.0.1 /24 --------Site 2 ---192.168.1.X
>
> I have seen examples where outside NAT allows me to translate address to a
> suitable address range on the inside. But what happens if the 2 x remote
> sites have the same IP's ranges (NB The above remote IP ranges belong to
> different companies).
>
> Can't see an expample on Cisco.com but still searching.
>
> How could I distinguish between the 2.
>
> Regards
>
> Darren



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