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English version below

J'ai 2 routeurs A et B relié en série avec les ip respectives ( 10.0.0.1/30 10.0.0.2/30) sur le routeur A j'ai activé la fonction NAT avec un pool (200.0.0.1 - 200.0.0.15/28).

Lorsque je sors je prends donc un ip du pool par exemple 200.0.0.10.

Comment ça fonctionne sachant que ma nouvelle ip (200.0.0.10) ne se trouve pas sur le meme réseau que mon interface de destination (10.0.0.2)?


English:
I have 2 routers A and B, interconnected with a serial connection, with the ip's 10.0.0.1/30 for A and 10.0.0.2/30 for B. On router A NAT was activated with the pool 200.0.0.1 - 200.0.0.15/28.

When connection to this router, I get an ip from the pool, for example 200.0.0.10.

Knowing my new ip is 200.0.0.10, which is not on the same network as my destination interface (10.0.0.2), how can this work?

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If you are asking a question or making a comment, please use the 'add comment' link below the relevant answer / Si vous posez une question ou faire un commentaire, s'il vous plaît utilisez le lien «Ajouter un commentaire" ci-dessous la réponse pertinente. –  Mike Pennington Jun 10 '12 at 12:28

1 Answer 1

up vote 2 down vote accepted

As you are connected to the 2nd router with this IP, your 1st router with NAT has DHCP enabled and it sends an IP to the 2nd router in 200.0.0 network too. Anyways, you should use private IPs in the RFC1918 ranges and not 200.0.0 subnet. As your 1st router is in 10.0.0 subnet, you could use it for everything.

In french: Comme tu es connecté au 2eme routeur avec ton IP, le 1er routeur avec le NAT envoie un IP au 2eme dans la subnet 200.0.0 aussi. Il vaudrait beaucoup mieux utiliser les adresses RPF1918 pour les IP internes. 10.0.0 des routeurs conviendrai parfaitemment.

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I already use private IP for routers "10.0.0.0 / 30" but my NAT pool is public IP "200.0.0.0 / 28" so my connection is under what networks? (10.0.0.0 or 200.0.0.0) the networks without NAT is working properly but when I enable NAT pool with the mentioned I don't know which networks take the upper hand over the other? –  PITCHY Jun 10 '12 at 9:43
    
The NAT network (200.0.0.0) has the DHCP so it will be used to give IP to machines that don't have a fixed IP in the same subnet. The network used will be the public one but this will work only if you own the public IPs and nobody else is using them. –  laurent Jun 15 '12 at 12:33

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