Local DNS server not possible with TPlink router (C80)
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Hello,
Associated to the router, I have a WLAN area and a small ethernet based network (with a switch) connected to the router through an ASUS repeater in client mode (called media bridge by ASUS), as it has better throughput than CPL. So in a way, everything should be WLAN. I have set up dnsmasq on the client mode/ethernet based network on a raspberry pi to resolve local names and forward to real DNS servers if this is not local. I have configured C80 dhcp server with local+my ISP DNS servers, that is 192.168.2.xxx as primary and ISP as secondary. It works well, every connecting device, windows or linux, gets the DNS servers right
But it only works partially. The pi hosting the DNS server works OK to resolve names. Another device connected to the switch works OK, request goes to the pi. Other devices connected directly to the WLAN or ethernet ports of the router do not work. I have used tcpdump and I clearly see the request to 192.168.2.xxx local DNS server and an answer mentioning local name was not found (therefore it resolves something like myrequest.net). But this request to 192.168.2.xxx never really reaches the local DNS. Therefore, it looks as if the request (when not on the switch) goes inside the router, which redirects it outside, gets an answer and forwards it back to the device. Why is it not letting the DNS request go to the switch network ? Any ping or ssh/rsync/samba/dlna request to the raspberry pi works well.
Of course, I could fill the etc/hosts file but local DNS server looked much smarter. Is it expected behaviour, that is router always route DNS requests to the outside rather to local devices ? Do I need another type of router ?
Regards
I made some progress during lunch. Enabling another pi allowed me to test other locations for the local DNS server.
If plugged directly to an ETH port of the router, things work nicely, that is WLAN and LAN clients on other ports get their request served correctly. If put back on the switch, that is behind the Asus AC55 media bridge, it works only on the switch.
I thought the AC55 was as transparent as my CPL connections or a switch but it seems not. It is true that I realized that it tends to mess up a bit the network map (where router says that IP adress of my NAS is given to the MAC address of AC55) while all the rest works fine:
- DHCP allocation to the NAS and address reservation
- Hosting DLNA server, domoticz server, samba on pi -> all the other clients see that correctly
- port forwarding: domoticz can be seen easily from outside
- ping/ssh work fine
On my 192.168.2.xxx network, AC55 is 192.168.2.yyy. Is there some routing rule I should add to have the DNS queries go to this kind of subnetwork ?
The ASUS AC55 is definitely not transparent as you can see from below netfilter rules. I understand the presence of DNS and http server as there is an admin web page at repeater.asus.com. But these services do not seem to then pass info to the real local DNS server.
Well, it is in fact weird. Every xx minutes, there are several seconds where my local DNS server gets the queries. Then it keeps failing
Solution:
- set AC55 as my local DNS server and set /etc/hosts. Just a work-around
- go to ASUS forums ;-)
- find a compact device doing client mode. All my devices are TPlink (router, switch, USB to eth dongle, wifi dongle, CPL, CPL wifi and a nano router with USB storage sharing for travel). I was thinking about RE205 but I have the impression that it will keep working as repeater while also allowing connection on ETH port. As it also repeats, is it not somehow impacting the throughput ? Will it connect nicely to a switch and allow to have my DLNA/domoticz/DNS/samba... server ?
