Dyndns and internal network routing

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gehenna

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#57326 9-Feb-2010 20:17

Hey, I'm curious about this more than anything, maybe some network guru can give me an answer.

I've got a server on my home network that I access at home and remotely. At home I use the internal IP or DNS name to get into it using RDP. Externally I use my dyndns domain name to get to my router, which then NATs me in to it.

I'm just curious - since my dyndns details are configured on my adsl router, is it smart enough to know if the RDP request is coming from the internal or external network?

For example: If I RDP the server from within my home network will the request go out to the internet and then come back in through dyndns to my router then my server? Or will the request go to my router, which then see's the dyndns request and routes it internally before it goes to the internet?

The reason I ask is that I often choose my Home shortcut instead of my Remote one while I'm out and about, or vice versa if I'm at home. If I can delete the Home one altogether and just use the dyndns shortcut that would save me some frustration

Also I don't want to have to use my internet bandwidth to RDP the server from home if I can help it - hence the home shortcut and this question in general!

What do you think?

freitasm

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#297499 9-Feb-2010 20:52

It depends on the router. Most routers won't be smart enough to route back to the LAN if they detect the IP is the one assigned to itself.

My suggestion? Forget about RDP, install LogmeIn Free (www.logmein.com...) and connect from anywhere, no port foward, more than one PC per LAN, etc.

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grant_k

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#297503 9-Feb-2010 21:02

gehenna: For example: If I RDP the server from within my home network will the request go out to the internet and then come back in through dyndns to my router then my server? Or will the request go to my router, which then see's the dyndns request and routes it internally before it goes to the internet?

I have a LinkSys router and it is smart enough to do what you say i.e. if I access my Desktop PC via VNC from within the LAN, using the external IP address (assigned using DynDNS), the router sees that the IP address used is assigned to its WAN port, so it routes the traffic directly, without going via the internet. I can tell this, because the WAN light on the router doesn't flash.

However, I still have two shortcuts set up on my laptop for VNC, one via the LAN and one via the DynDNS address, because that way I can configure the connection appropriately for use via the internet (with a restricted colour pallette) or via the LAN (with a full colour pallette). Then when I'm away from home, I'm not using unnecessary data traffic via my Mobile Broadband modem.

freitasm

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#297509 9-Feb-2010 21:28

Do you have Linksys running stock firmware or DD-WRT?

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#297544 9-Feb-2010 22:55

Just the stock firmware that came with the router. I never changed it since buying it in Oct 07.

drou

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#297600 10-Feb-2010 10:59

I think that the router route the packets to internet...Because must to know what IP address belong to xxxx.dyndns.org from the dyndns.org homepage... Forward the request to those DNS and establish the connection in the WAN port....And (i'm not sure) the router never send/receibe the packets in the same inteface..
(sorry about my english i'm from Argentina...)

Ragnor

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#297676 10-Feb-2010 14:52

Many routers support NAT loopback in their stock firmware in addition DD-WRT, Tomato and OpenWRT do also.

Dyndns conveniently has a support page about loopback problems with some alternative solutions if your router doesn't support NAT loopback
http://www.dyndns.com/support/...

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aellis

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#297841 11-Feb-2010 02:16

Most Linksys routers will handle the Loopbacks with your NAT properly so you should be able to use just the one shortcut.

IRT the mention about our loopback issue article, it essentially talks about how to edit your hosts file so you can have your hostname resolve to your internal IP, instead of going through the router, when you are on your LAN but that's really for desktops that remain on the LAN.

gehenna

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#298034 11-Feb-2010 17:28

Turns out after doing some traceroutes and some other sniffing that my router is capable of it as well, it basically routes from internal interface, to external and back to internal all on this side of the network. Quite cool really.

Logmein is fine and I use it here and there to administer family computers but it's not really suitable for what I need to do here on my own server.

sultanoswing

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#299511 16-Feb-2010 14:49

IMHO, it's more 'sexy' to avoid middle-men third parties, such as logmein, when it comes to connecting home-to-road PC's and networks.

But that's just me enjoying the features and freedom of dd-wrt, putty and openssh - fun times!

webwat

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#300967 22-Feb-2010 12:52

The DNS resolves a name to the router's external IP address, so if you go to that IP address from inside your LAN then you always get to the router and no further (although the DNS resolution is done on internet). A lot of routers dont do NAT loopback like yours does, but still pointless to rely on DNS for a local address that doesnt change. The local address still works even if your internet isnt stable.

Time to find a new industry!