[RT-AC66R] [380.66] Is it DNS?

[Digital Noise]

I've got a situation that has me banging my head against my laptop and so I humbly come before people who are smarter than I am.

I'm having an issue where clients are successfully getting DHCP IP addresses from the router, but their host names are not being registered in DNS correctly despite being configured correctly on the client side. The RT-AC66R is set as the default gateway for all clients, and none of the clients in question have DNS server entries manually set.

To my admittedly limited understanding, the process should work like this:

1. Client requests IP from DHCP server and includes the configured hostname with the request.
2. DHCP server assigns IP address from pool, and registers/maps the hostname to the IP address.
3. Other clients on network that are configured to use the router as their initial DNS server should then be able to resolve other clients by hostname.

But what's actually happening is something akin to this:

1. Client requests IP from DHCP server and includes the configured hostname with the request (presumably)
2. DHCP server assigns IP address from pool, and seemingly ignores the hostname provided with the request.
3. Other clients on the network can only access the client via IP, and not hostname.

I can't seem to figure out why this is happening, and to make matters even more confusing, occasionally it will resolve itself seemingly out of nowhere. Or, as in the case I've got right now, we're going on day three and I still can't resolve via hostname, only IP.

Is there something I can look at on the router side to see if there's a reason why the requested hostname isn't being mapped to the assigned IP?

 

[john9527]

In order for local name resolution to work, you have to be using dnsmasq (the router caching nameserver) as the DNS server. Two things to check
- If you are using custom nameservers, make sure they are entered on the WAN page, and NOT the LAN/DHCP Servers page.
- If you have set alternate nameservers using Parental Controls, you are bypassing dnsmasq and local name resolution won't work.

 

[Digital Noise]

In order for local name resolution to work, you have to be using dnsmasq (the router caching nameserver) as the DNS server. Two things to check
- If you are using custom nameservers, make sure they are entered on the WAN page, and NOT the LAN/DHCP Servers page.
- If you have set alternate nameservers using Parental Controls, you are bypassing dnsmasq and local name resolution won't work.

So far as I know I'm using dnsmaq - like I said, none of the other clients are having this issue at the moment. DNS Server 1 & 2 on the LAN/DHCP page are empty, and I'm not using Parental Controls at all.

Something has occurred to me, however - the client in question is a TurnKey Linux appliance, which comes with the appropriate iptables rules already configured - since I know that DNS queries use port 53 by default, and presumably DNS registration would as well, could the following default rules be blocking DNS registration from the client? I'm very much a n00b when it comes to iptables and I'm trying to work on that.

root@mineos ~# iptables -L
Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:8443
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:25565
ACCEPT     all  --  anywhere             anywhere             state RELATED,ESTABLISHED

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

 

[bbunge]

I have noticed with Merlin 380.66_4 that the unit names when reserving IP addresses are different. My Ubuntu server comes up as Dell and not the system name ubuntu and my NAS shows WESTERN DIGITAL and not mybooklive.

Sent from my P01M using Tapatalk

 

[Digital Noise]

I have noticed with Merlin 380.66_4 that the unit names when reserving IP addresses are different. My Ubuntu server comes up as Dell and not the system name ubuntu and my NAS shows WESTERN DIGITAL and not mybooklive.

Sent from my P01M using Tapatalk

I've seen something similar - the MAC address being used for these clients that aren't having their hostnames used.

What I don't understand is why - if the client is configured correctly, then dnsmasq should be using the values that the client supplies.