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Routing issue when accessing from same network

Unanswered Question
Apr 10th, 2012
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I couldn't find a more decent title, I just can't explain it better.


This is the situation:

Cisco 2800 with WIC card,

ATM (ADSL) --> Dialer interface --> NAT with overload and Port Mapping --> Local ethernet


The issue:

I mapped port 80, DNS is fine, but I can't access the resource from the local network.

I try accessing mydns.info from the local network, nothing works. If I try accessing it from the internet all is fine.

DNS resolves fine, but packets as I see son't exit from the router. a traceroute gives me this:


traceroute  82.61.hey.253

traceroute to 82.61.hey.253 (82.61.hey.253), 64 hops max, 52 byte packets

1  192.168.0.120 (192.168.0.120)  1.886 ms *  2.338 ms


Is there a way to force the router to exit the network and ignore the routing table's entry? I need to access my resources using the external IP, so I can check if everything is working.


Thank you!!!!

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nkarpysh Tue, 04/10/2012 - 18:39
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  • Cisco Employee,

Hello,


If you traceroute stop on the first hop that does not necessarily mean that packet also stops there. Traceroute is UDP and rely on ICMP unreachable's sent from each hop. If UDP is blocked or no ip unreachables configured on the further hop - then you will not see any traceroute reply. SO this is not reliable test.


So you have your DNS resolved - good. Now keep in mind that connection to Internet is not only traffic forwarded to Internet but also traffic being sent from Internet to your source address and you need to check that both flows are working.


First check the forward traffic - see if your router has a correct route/default route to Internet ip address. Then make sure you have correct NAT on your router.


Basically you can configure router to do Policy Based Routing - to send particular traffic to the next hop which you explicitly specify - in that way outer will not rely on it's routing table. But this will depend on the router model.


Configs and show commands may help to look at your problem deeper.


Nik

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