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Tag: nat

Cisco IOS NAT Virtual Interface

Up until recently, I’ve had ADSL at home for some years. For the last year or so, I’ve used a Cisco 1812 as my router (the ISP-router was put into bridge-mode). A few weeks ago, when I got a 10/10Mbps fiber-connection, it suddenly became more relevant to host some services at home (why pay for web-hosting, when you can host it home, for free?). As a result of this, I stumbled upon a ?problem? that annoyed me a bit; loopback-support ? the ability to reach your services using your external IP, and hence applying port-forwards (this way you could use ?ssh externalip -p port number>? regardless if you are home or not). This is quite useful if you move between different networks a lot (e.g. using a laptop ? which was the case for me). This feature is known as tromboning, or hairpinning, and is something that often works on cheap routers you get from your ISP. So, why shouldn’t this work on a Cisco-device?

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