name resolution problem

English Network/Internet
#1

Hi there,

I have a name resolution problem. The situation is:

PC(192.168.178.21) <–(WLAN)–> FritzBox(192.168.178.1) <–(LAN)–> nas1(192.168.178.22)

My PC connects to a FritzBox via WLAN. The FritzBox serves as DHCP server and more to that as DNS server. As soon as I am connected I find the corresponding entry in my /etc/resolv.conf: nameserver 192.168.178.1

So far so good. :slight_smile:

My external storage is a NAS which is connected to the FritzBox via LAN. Its name is nas1 and it recieved IP 192.168.178.22 from the DHCP server.

The problem is: although I can dig/nslookup/host for nas1 (the name is perfectly resolved by the FritzBox), I am unable to ping nas1: unknown host. This is also true for browsing via an internet browser.

I’m sure there is a simple explanation for this, I just wasn’t able to find it. :expressionless:

All hints how to solve this are highly appreciated!

Thanks in advance,

Reinhard.

#2

This can’t work. Your WLAN is on the same network as your LAN. These should be two different networks.

#3

To prove this try to ping to the IP address instead of to the name. This will show you that it is not a name resolution problem (as you already proved by using nslookup, but a connection problem (that is where ping is for).

#4

All devices are in the same network, IP communication is fine. (Tested with ping / IP addresses).

Name resolution still gives me a hard time. Is it possible that ping works different from nslookup/dig/host?

Cheers, Reinhard.

#5

Yes, ping works different. ping uses the gethostbyaddress() function which uses not only DNS but also /etc/hosts (and other resources). The config for this is in /etc/nsswitch.conf. There it is configured where to look first (e.g. look first in /etc/hosts, when not found use DNS, when again not found fail).

nslookup and the like do what they say, looking in DNS only.

#6

Hi there,

thank you for your inputs! With the help of wireshark, I finally found the source of the problem: ping automatically adds the search domain (.mydomain.local) and this of course confused my DNS server on the FritzBox because Fritzbox does not know that.

So I removed all entries of .mydomain.local - I even had to reboot since restart of network services and netconfig update did not help. After the reboot, ping ask for nas1 instead of nas1.mydomain.local and everything is fine … for now :wink:

Thanks again!

Reinhard.

#7

You are welcome.

Not all those domains, names, etc. installed automagically, so newbies do not have to think about their configuration, are a blessing IMHO.