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Old 01-19-2015, 11:39 AM   #1
Michaelx
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Question demistify: LAN name resolution


Hi, i own a very small LAN, 1 PC + 1 NAS and two Routers,D-Link Router(LAN-internal) and 1 external Router, which goes out to the WORLD WIDE WEB.

Now, i discoverd that if i use my internal D-Link Router as a GATEWAY (GW) ;a nmap-command shows not only IP-Adresses, but also hostnames of the connected devices (NAS+Router).

But if i configure my external Zyxel-Router (the one that connects to the internet) if don't get the name resolution working ( i meant to say : no hostnames are beeing shown if i issue a nmap-command, but ip-Adresses only).

Quote:
nmap -sP 192.168.1.1-5

Starting Nmap 4.20 ( http://insecure.org ) at 2015-01-19 18:32 CET
Host 192.168.1.1 appears to be up.
Host 192.168.1.3 appears to be up.
Nmap finished: 5 IP addresses (2 hosts up) scanned in 0.556 seconds

So i wonder how my PC detects the hostnames of the connected devices if use the internal Router as a default GW (Gateway).
And i also wonder which deamon(service) maybe running on my internal Dlink-Router (ADSL 2+ 2741B) that enables my PC to see hostnames of the connected devices.

Quote:
nmap -sP 192.168.1.1-5

Starting Nmap 4.20 ( http://insecure.org ) at 2015-01-19 18:32 CET
Host Dlink(192.168.1.2) appears to be up.
Host NAS(192.168.1.3) appears to be up.
Nmap finished: 5 IP addresses (2 hosts up) scanned in 0.556 seconds

Please are you able to clearify this for me ?

Thank you.

Last edited by Michaelx; 01-19-2015 at 12:13 PM.
 
Old 01-19-2015, 11:44 AM   #2
dijetlo
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Your dlink router is passing out IP addresses.
Therefor it knows the hostnames. It has a list of leases it's farmed out, it's reading from the list.
The internet router has no such list.
 
Old 01-19-2015, 12:00 PM   #3
Michaelx
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dijetlo:

The Dlink Router has no DHCP-Server enabled. If this is what you are you refering to , is it ?

Number of Dynamic DHCP Clients : 0

But two entries follow, and one entry shows the NAS-hostname

Last edited by Michaelx; 01-19-2015 at 12:06 PM.
 
Old 01-19-2015, 08:02 PM   #4
dijetlo
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Where are they polling IP address from if not the dlink?
 
Old 01-19-2015, 10:05 PM   #5
onebuck
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Moved: This thread is more suitable in <Linux - Networking> and has been moved accordingly to help your thread/question get the exposure it deserves.
 
  


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