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Using a DLink 2640-T (ADSL2+Router). It cant resolve the internal hostnames. The manual is pointing to the firewall settings of the router to switch off the DNS-Blocking from external (which doesnt make sense to me). But even with that in place it just does not work. And all I got from DLink support: Please reset and try again... What I did, no change. Thanks for any advice

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which system exactly is DNS serving your internal hostnames? – Alnitak Jun 3 '09 at 6:47
The router itself does the internal DNS, as well forward to the outside DNS Server (ISP). – javadude Jun 3 '09 at 7:39

I seriously doubt that the D-LINK 2640-T has a built-in DDNS server. According to the Datasheet on that product it has DNS Relay support, and DDNS. The DDNS functionality is implemented as a DDNS client to update public DDNS sites so that your External IP of the DSL Router can automatically update DNS records on the Internet. I doubt they include a DDNS server that allows your "internal" clients to self-register with teh DSL modem/router device.

The DNS relay portion is to permit your "internal" clinets to point to the DSL router/modem and have it forward queries recursively to the Internet for resolution.

You will need to either use hosts files or run your own Internal DNS server.

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Your clients DNS settings should be pointing to the Dlink router's IP address, so that the client asks your router for names. The router should reply all internal names to your client, and should use your ISP's DNS servers for external lookups. I'm not sure that "DNS-Blocking from external..." has anything to do with it.

Are your client computers able to register in DNS? What OS are they running?

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The DNS config of all clients is pointing to the router. Mixed environment of Ubuntu, Windows XP and Linux Enterprise 11. Thanks – javadude Jun 3 '09 at 6:42
Firmware update from V3.02B01T01.EU-A.20071212 to actual V3.02B01T01.EU-A.20080725 did not solve problem. – javadude Jun 3 '09 at 8:38

In your case I'd strongly suggest running a real internal DNS server, rather than rely on the forwarder built into your router.

See my document draft-ietf-dnsext-dnsproxy for the whys and wherefores.

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Thanks.Pretty comprehensive document.You might be right. – javadude Jun 4 '09 at 0:19

+1 to what netlinxman said -- either an internal DNS server (harder) or entries in each machines host file (easy) is probably the way to go.

Alternatively, if these on Windows machines then turning on WINS should allow them to find each other.

The page for the 2640B version of this product does say that it supports DDNS, but this is for inbound access from the internet.

d-link TV vido explaining DDNS:

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Answering my question (after continue the hard way learning about networking, which I am not expert in)

The router supports the internal DNS relay provided the clients are in the same workgroup ! This is straight forward for Windows clients. But Ubuntu, or better Linux, doesnt really now about the workgroup concept (I guess) until you install/activate samba.

Ubuntu: sudo apt-get install samba

Check /etc/samba/smb.conf for workgroup setting.

Now I can ping the Linux clients from the Windows clients (fast), but the reverse is very slow! "ping windowshostname" or ping "anylinuxname" from linux host results in a 2..3 seconds waiting time followed by very slow response times. Maybe I ask as another question here ..

Thanks for your feedback !

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The DNS relay does not work this way. If you are getting name resolution, it's not b/c of the D-LINK device. When you installed the Samba package you probably enabled the nmbd service as well. It sounds like you are achieving name resolution via NetBIOS over IP. If everyone is part of the same workgroup and local subnet, you will get resolution of any clients that have NetBIOS over IP enabled b/c they will perform local subnet broadcasts for name challenge and resolution. The reason it takes so long is b/c DNS and other hostnaming has to fail first. – netlinxman Jun 10 '09 at 3:04
I believe my first response is still the correct response. The DNS relay function is to permit you internal clients to point to the D-LINK and have it forward or "relay" their DNS lookups for public Internet resolution. It is not intended for resolving your internal clients. It can't b/c it is not configured to be Authoritative for any DNS zone(s). It doesn't have any DNS code that allows clinets to self-register their names and IPs with it. – netlinxman Jun 10 '09 at 3:07

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