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Grant Edwards wrote: |
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> I don't understand why I have to do NAT. Can you explain why? |
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> (Or point me to docs that explain why?) |
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> |
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router01.your.network.com |
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eth0 - 10.11.12.1 |
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eth1 - 24.1.2.231 - Comcast |
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eth2 - 64.1.2.132 - Speakeasy |
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Naturally RFC 1918 space is useless outside your network so you have to |
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NAT. However you need to make sure that you are making your policy |
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routing decisions at eth0. You don't want traffic marked as originating |
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from 24.1.2.231 going out eth2 since Speakeasy could (and should) drop |
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traffic that is not origination from its IP space. Additionally traffic |
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will be routing back to your via Comcast connection resulting in |
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asymmetric routing which can increase the chances of packets arriving |
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out of order. |
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router01.your.network.com |
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eth0 - 24.2.3.1/29 |
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eth0 - 64.2.3.1/29 |
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eth1 - 24.1.2.231 - Comcast |
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eth2 - 64.1.2.132 - Speakeasy |
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Same case with this setup even with real IPs. The chances of convincing |
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any ISP to accept routes smaller than /24 from you are tiny. And finding |
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anyone who knows what you even want to do even when you have the IP |
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space is pretty much non-existent. I know, I've tried. Same thing in |
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this case, you'll NAT at eth1 and eth2 and policy router at eth0. |
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If you are doing this from a single machine with two IP's and no other |
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networks or interfaces, it should just work. Linux should use the IP of |
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interface the packet leaves from, but I'd use tcpdump to make sure. |
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kashani |
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-- |
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