Local DNS issues

  • ATTENTION! As of November 1, 2020, you are not able to reply to threads 6 months after the thread is opened if there are more than 500 posts in the thread.
    Threads will not be locked, so posts may still be edited by their authors.
    Just start a new thread on the topic to post if you get an error message when trying to reply to a thread.

acbeers

New Around Here
I have a AC86U running stock firmware, and I'm having local DNS issues. Some names will resolve and some will not. I've noticed that clients that are labeled "DHCP" in the clients list have names that will resolve. Those marked "static" and "manual" will not.

I've also noticed I have many clients labeled "Static", even those with automatically assigned IPs inside the DHCP range, which I can't explain.

So, I have two questions for the forum:
- why are many clients listed as "Static" on the clients page, even when they are in the DHCP range?
- why don't any names resolve for non-DHCP clients?
 

dave14305

Part of the Furniture
DHCP clients can appear as “Static” in the GUI if the router or dnsmasq (DHCP server) are restarted since the client has last requested a DHCP lease or renewal. I imagine it will heal itself within 24 hours (if that is your lease duration).

I don’t know that you would normally expect a static client to be resolvable by the router’s DNS if the IP is not handed out by DHCP. It’s an interesting question since I know some OS and DNS servers can handle dynamic registration, but I don’t know how ASUSWRT would behave. The ASUS GUI might recognize the client’s name in the Network Map Client List, but it doesn’t mean it‘s propagated to dnsmasq for resolution on the LAN.

You could set phony DHCP reservations for those static IPs and define the hostname there so that it gets configured in the DNS server... The static client will never request the IP via DHCP, but it’s still defined in DNS. On second thought, I’m not sure if this is a stock feature or something from Merlin’s firmware...
 

OzarkEdge

Part of the Furniture
I have a AC86U running stock firmware, and I'm having local DNS issues. Some names will resolve and some will not. I've noticed that clients that are labeled "DHCP" in the clients list have names that will resolve. Those marked "static" and "manual" will not.

I've also noticed I have many clients labeled "Static", even those with automatically assigned IPs inside the DHCP range, which I can't explain.

So, I have two questions for the forum:
- why are many clients listed as "Static" on the clients page, even when they are in the DHCP range?
- why don't any names resolve for non-DHCP clients?

The client list has historically been a bit off. I just checked mine and its one Static and the rest DHCP is correct for a change. So, maybe the RC2-9 beta firmware is improving things.

I'm not sure what you are referring to when you say names don't resolve. My clients look like this:

1609389029535.png


OE
 

acbeers

New Around Here
I've since configured the router for ssh access and I've been looking around, and noticing regular restarts. That would explain the above - addressed handed out by DHCP before the reboot are forgotten, so aren't in dnsmasq and so therefore don't have resolvable names. Perhaps I need to get to the bottom of the restarts first!
 

acbeers

New Around Here
OazrkEdge - for me, clients that have DHCP next to them can be referred to - e.g. "ping OBi202" or "ssh OBi202". I've just understood my problem to be primarily that my router won't stay up for more than ~10 minutes without restarting, forgetting all of the clients to which it handed out a DHCP lease.
 

OzarkEdge

Part of the Furniture
I've since configured the router for ssh access and I've been looking around, and noticing regular restarts. That would explain the above - addressed handed out by DHCP before the reboot are forgotten, so aren't in dnsmasq and so therefore don't have resolvable names. Perhaps I need to get to the bottom of the restarts first!

Firmware 82072 is known to have installed as an auto update... not common. I don't know if this figures into any restarts. Maybe a reset to factory defaults and reconfigure from scratch is due. And consider the current firmware.

OE
 
Last edited:

OzarkEdge

Part of the Furniture
OazrkEdge - for me, clients that have DHCP next to them can be referred to - e.g. "ping OBi202" or "ssh OBi202". I've just understood my problem to be primarily that my router won't stay up for more than ~10 minutes without restarting, forgetting all of the clients to which it handed out a DHCP lease.

I understand you now. No, I can't ping any of the client names in my client list. I always considered those to just be labels/names.

OE
 

cptnoblivious

Regular Contributor
If you have name resolution issues on the client, go to one that's having problems, open a command prompt and type ipconfig /all, see what the DNS server is set to.

Compare that to your DHCP settings on the router. See if they match.
 

acbeers

New Around Here
Hey everyone - the core issue here was frequent restarts, which would cause DHCP client names to be forgotten until the lease would renew. It was restarting often enough (few times per hour) that most client names would be forgotten. The issue appears to have been the attached USB drive which was being used for Time Machine. The logs led me to believe this, so I took the drive off and the restarts stopped happening.
 

bluzfanmr1

Senior Member
Hey everyone - the core issue here was frequent restarts, which would cause DHCP client names to be forgotten until the lease would renew. It was restarting often enough (few times per hour) that most client names would be forgotten. The issue appears to have been the attached USB drive which was being used for Time Machine. The logs led me to believe this, so I took the drive off and the restarts stopped happening.

That sounds like the router running out of memory while running Time Machine backups. Do you have a swap file? Not sure if you can do it on stock but with Merlin firmware you can and it may alleviate the rebooting issue.
 

cptnoblivious

Regular Contributor
There's still a question on why name resolution would be having issues. No matter what, if a DNS server is handed to the client, and that DNS server is responsive, it shouldn't matter unless there is some sort of IP Address conflict.

Glad that there's a solution, but I'd still be curious why name resolution is impacted. :)
 

acbeers

New Around Here
Not sure on swap space - I've also moved to BigSur, which changed the supported filesystem for Time Machine (AppleFS instead of HFS) - not sure if Merlin supports that new FS.

re: name resolution - earlier posters hit on that. local names for machines registering via DHCP are entered into dnsmasq, which stores them in memory. On reboot, these are all forgotten, and clients that haven't renewed their leases are listed as "static" (i.e. IP given out my someone else) vs. "DHCP" (i.e. IP given out by the router)
 

Latest threads

Sign Up For SNBForums Daily Digest

Get an update of what's new every day delivered to your mailbox. Sign up here!
Top