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eldridge
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Strange Routing problem

Fri Jul 21, 2006 12:42 pm

Hi Guys

Have 2 mikrotiks setup wirelessly over a 15km link. Registration is good and communication working fine. Using no Firewall rules or Routing protocols. Got all the routes as static routes. IP address on Miktrotik1-wlan is 192.168.50.254 and on Mikrotik2-wlan is 192.168.50.253. Got static routes on Miktrotik2 to pass any traffic going to 10.* to 192.168.50.254.

Here's the strange thing. Clients sitting behind the Mikrotik2 on the LAN can ping and connect fine to any 10.* ip. Traceroutes show the correct path. But if i try and traceroute or ping from the Mikrotik2 router itself, i get a time-out. It shows me on the traceroute that it hops to 192.168.50.254 (other side of the wireless), but from there it times out. From the Mikrotik1 i can ping and connect to any 10.* ip, because the routes are there.

Any idea why i can connect everywhere from anywhere except from the Mikrotik2 router (and he is routing it through him)?

Any ideas would be appreciated.
 
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Eugene
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Mon Jul 24, 2006 12:19 pm

Because the packets originated from the router have different source address from packets coming from attached LAN.
 
eldridge
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Mon Jul 24, 2006 6:58 pm

Thanks for the reply Eugene. But still doesn't make sense to me. Static routes that i've added works on Destination IP address. Doesn't care where the packet orginates from (source). On the Mikrotik1 router i can ping devices everywhere (even devices sitting behind the Mikrotik2 router).

The ping from the Mikrotik2 router does hit the static rule and crosses the wireless link to the ip other side the link, but from there it dies. The Router should look at the destination ip in the packet and route it accordingly.

Am i missing something. Is source based routing somehow involved. My traffic is flowing 100% fine at the moment, but i need to sync my Mikrotik2 router with a NTP server that i can't reach on the other side of the network.
 
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tneumann
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Mon Jul 24, 2006 9:28 pm

But still doesn't make sense to me. Static routes that i've added works on Destination IP address. Doesn't care where the packet orginates from (source).
Yes, routing is usually based on the destination address, but exactly that is also true for the return traffic (for example the reply to your ping request), and then what has been your source address will become the return traffic's destination address, and there has to be a route for that as well.

Always check your routing bidirectionally.

--Tom

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