Topic: dynamic DNS behind another gateway

[Gordon]

All,

It has become clear that dynamic DNS is not an option if my Linux has a static IP.  My SME server is connected to a DSL modem/router combination with a firewall.  I can configure the SME server to accept DHCP and specify a dynamic DNS provider (dyndns.org), but the Linux cant reach the internet (the test fails) even though it reaches the rest of the LAN.  

Any ideas?

Thanks in advance.

Gordon.

[Tom Veitch]

Gordon,

Can you ping the gateway box and does it have internet access,


Tom

[Gordon]

Tom,

Yes.  The gateway box and the rest of the LAN (apart from Linux) have
internet access, and every address (including Linux) can be pinged.
If I configure Linux in server only mode with a static IP address, it works
fine, but no dynamic DNS.

Thanks

Gordon.

[Bill Talcott]

Does the SME have a private or public IP address? Dynamic DNS services are designed to point a domain name at your computer all the time, regardless of IP changes. Rather than having to type http://1.2.3.4 to get to your website the first time, then http://1.2.3.5 the next time, and http://1.2.3.6 the next, and so on. Instead of finding some way to tell people what your IP is and then having them use that, dynamic DNS points a domain name at whatever your current IP is.

If people from the internet can't access your server by its IP address (private IP), then having a dynamic name pointing at that IP isn't going to do you any good.

[Gordon Chatterton]

Bill,

Thanks for your reply.  The address is public.  What I meant to convey in my last post was, if I configure the SME in server only mode, and provide it with the IP address of the gateway box, it can reach the Internet.  With the correct ports opened up, I can host websites and run mail exchange all day long.  

However, each time my ISP changes my Internet address, I have to manually go to the dynamic DNS provider (dyndns.com) and update the host name myself.  Server only mode does not give me the option of turning on the SME built in dynamic DNS service which would automatically send that update to dyndns.com.  

Do you know if I can change the configuration files so that I CAN turn that feature on in Server only mode?

Thanks again.

Gordon.

[Charlie Brady]

Gordon Chatterton wrote:

> Do you know if I can change the configuration files so that I
> CAN turn that feature on in Server only mode?


How is the server to know when the gateway gets a new address, and learn what that new address is?

Charlie

[Gordon Chatterton]

>>How is the server to know when the gateway gets a new address, and learn what that new address is?<<

Good point.  Although I dont know enough about the dynamic DNS logic to say it isnt possible for the program to query the gateway box and determine the current Internet address.

Assuming it can't, I suppose that means the only configuration that supports dynamic DNS is if the SME server IS the true gateway.  

What about using a client from another machine on the LAN?  Does anybody have experience with something like this?

Thanks again.

[Charlie Brady]

> What about using a client from another machine on the LAN?

Exactly the same problem exists - how is the client to know that the address has changed, and what it has changed to.

Charlie

[Gordon Chatterton]

The first client I looked at indicates it features: "local & remote IP detection with dsl/cable router support."  (DirectUpdate v.3.5.6)  I havent tried it yet.

[Bill Talcott]

I'm confused. Does the SME have a public internet IP address, or does the gateway have a public IP and stuff is forwarded to the SME's private IP behind the gateway?

If the SME has a public IP, then it's just a matter of gaining access to the dynamic DNS stuff while in server-only mode. If the SME has a private IP, then you'd have to find out the new IP from the gateway somehow, and have the software pass that for the update.

It seems like it should be fairly simple to make the dynamic DNS stuff work in server-only mode, though I haven't looked at it myself. Everything is already there, and I'm assuming it's basically just "turned off" in that mode. I'd guess you'd just have to manually add a command or enter a setting somewhere to enable it. Just my random guesses though...

[Gordon Chatterton]

>>It seems like it should be fairly simple to make the dynamic DNS stuff work in server-only mode, though I haven't looked at it myself. Everything is already there, and I'm assuming it's basically just "turned off" in that mode. I'd guess you'd just have to manually add a command or enter a setting somewhere to enable it. Just my random guesses though...<<

The gateway box has the public IP and passes information to the SME server's private IP.  I agree the option should be able to simply be turned on in server mode, since the clients available for dynamic DNS are able to get the public IP address from the DSL modem/router.  

I dont have the slightest idea though what kind of command that would look like however.  

Gordon.

[Bill Talcott]

Gordon Chatterton wrote:
>
> The gateway box has the public IP and passes information to
> the SME server's private IP.  I agree the option should be
> able to simply be turned on in server mode, since the clients
> available for dynamic DNS are able to get the public IP
> address from the DSL modem/router.
>
> I dont have the slightest idea though what kind of command
> that would look like however.
>
> Gordon.

Ok, then you will need to have the dyndns client (on whichever box you choose) check the gateway for the updated IP. There are programs (like the one at mywanip.com) that will show your internet IP, even behind a router. And like you pointed out, it looks like even some of the clients can do it. While it would probably be nicer to have the server updating the dyndns stuff, it'll probably be easier with one of those other clients on a PC for now (since the SME script doesn't support the remote IP detection).

[RICHARD]

hi,
im using dns2go dynamic service,
ive got one client on my sme gateway serveur xxx.dns2go.com, and another one on one windows computer on the lan yyy.dns2go.com.

Both url are functionnal and points to the ip given by my provider. So i think that could be your answer

[Gordon Chatterton]

Thanks, that's what I ended up doing, and it works great.  If anybody ever comes up with a command to customize the SME server in this regard, I would still love to know about it.  

Gordon.