IPV6 DNS Bug?

[rich09821]

Running RT-AC87U

I'm not sure if this is a bug or expected behavior, but when manually specifying DNS servers, no matter what I specify all of my IPV6 clients end up with the DNS server as the router's LAN IPv6 address instead of the values I specified. This is causing problems with some internal clients not hitting an internal DNS server for name resolution. I'm forced to manually set the IPv6 DNS server address on those clients.

I see the same behavior in the offical asus firmware versions as well.

If anyone has any thoughts on how to fix this, please let me know. If there's a script I can run, I'd be happy to.

 

[microchip]

this is expected behavior since the router functions like name resolver (DNS) device for everything attached to it but everything going out of the router uses the properly specified DNS servers you told the router to use

it's the same for IPv4, not just IPv6. Here on Linux in /etc/resolv.conf I have 192.168.1.1 as "DNS server" (read: router does the work)

 

[rich09821]

While that may be true, internal clients still can't use that IPv6 address to route in some cases. For instance, if I manually type in the IPv6 address on a client for a DNS VM that I have in my network, name resolution for my internal clients works just fine. If I toggle the DNS address back to autoconfig it uses the LAN IPv6 address of the router and name resolution for the internal clients fail.

Also, with IPv4, if I specify different DNS servers in the router, on my windows clients I can see the IPv4 DNS addresses that I've specified. The IPv6 address just shows the IPv6 address of the router.

 

[mlai]

While that may be true, internal clients still can't use that IPv6 address to route in some cases. For instance, if I manually type in the IPv6 address on a client for a DNS VM that I have in my network, name resolution for my internal clients works just fine. If I toggle the DNS address back to autoconfig it uses the LAN IPv6 address of the router and name resolution for the internal clients fail.

Also, with IPv4, if I specify different DNS servers in the router, on my windows clients I can see the IPv4 DNS addresses that I've specified. The IPv6 address just shows the IPv6 address of the router.

I have this problem as well. Something the router is not resolving right. I have internal DNS server on a Synology, which it also resolves some of my remote office addresses. Even when the ASUS routers (I tried it on AC66U/AC68U/AC87U) are set using the synology as DNS resolver, the router does not resolve the non-local office machines to IPv6 addresses, but directly using the Synology DNS will.

 

[rich09821]

mlai, your IPv4 DNS addresses are set correctly though, right? Just issues with IPV6?

 

[mlai]

mlai, your IPv4 DNS addresses are set correctly though, right? Just issues with IPV6?

Well.... Not with the router....

Setup is that DHCPv4 on my LAN is handled by Synology as well. All LAN clients get their IP configs from synology which tells them to use synology as the DNS resolver. So the clients have no trouble resolving IP addresses, as they do not use the ASUS router.

The ASUS router itself is ALSO configured to use the LAN IPv4 address on the synology as a dns. But everything I use nslookup, manually set the server to the router, and query a resolvable remote office name from the Synology DNS, the router will give a negative return. Local resolvable address from Synology DNS (via router DNS server) resolve fine.

This happens on both the IPv6 and IPv4 address of the router.

Major pain in the rear end for IPv6, as I rely on the router to provide stateless info and the router keeps on insisting broadcasting itself as the IPv6 resolver instead of the local synology DNS server IPv6 address.......

However, you can mitigate the problem by using postconf script. I did use the dhcpv6.postconf and replace the broadcasted router IPv6 DNS address with the Synology Address........

 

[mlai]

Update. I flashed back to ASUS firmware 378.3885 on my AC87U. I find that if I change the WAN DNS to manually specifying the IPv4 of my Synology DNS, all my clients pointing at the router for DNS resolution will still properly resolve local and remote hostnames set in the Synology DNS server even when their DNS is pointing at the IPv6 address of the router......

For some reason, the ASUS router itself still using IPv4 setting for DNS queries despite what is set in the IPv6 pages.......

 

[rich09821]

I just reverted back to 378.3885, however now I'm seeing that my windows clients aren't keeping their IPV6 addresses. If I do a ipconfig /renew6, I'll get my IPV6 address back, but after awhile the IPV6 address just disappears.

Do you see the same behavior?