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E Karlson

New Around Here
I recently decided to try outIPv6 on my home network, so I bought an ASUS RT-AC88U and deployed it as the router for my home network.

First thing was that the firmware had to be updated to the latest version (3.0.0.4.382_15850). Once that was done connecting to Comcast was straightforward ("native" IPv6 - otherwise known as SLAAC - wish ASUS would use the standard terms for these things).

First thing I found - when using DHCP-PD to pick up the IPv6 prefix from the ISP, it takes the /56 prefix from the ISP and turns it into a /59 prefix that it binds to the inside port by adding three 1's to the ISP prefix. No way to control or configure this that I can find. Not causing a problem at the moment, but it sure would be nice to be able to configure that behavior. If one has a static IPv6 prefix, one could turn off DHCP-PD and manually configure it, but that won't work if the ISP prefix is not static.

Second problem, and this is the real one: there are almost no options for configuring the RA options. There are several issues here.

Issue #1: The RT-AC88U makes *itself* the DNS server for the IPv6 network (via an RDNSS tag on the RA). Wrong. I have my own internal DNS servers that know about my internal, private domains. I need those to be the advertised DNS servers, not the ASUS unit. I can sort of work around this by manually telling the ASUS to use my DNS servers instead of the ISP servers, but this still leaves the ASUS unit in the middle of my DNS resolution (does the ASUS cache DNS responses? If so, what is in the cache? How does one flush the cache?).

Issue #2: The ASUS has no ability to configure a DNSSL tag on the RA, so I cannot advertise my internal domain names to my internal hosts for DNS resolution.

Issue #3: In terms of managed IP address assignment, the ASUS only allows for two options. The first is that the 'M' bit is cleared with the 'O' bit set and the 'A' bit set. The second is that the 'M' bit is set with the 'O' bit set and the 'A' bit cleared *AND* the ASUS now acts as a DHCP6 server. As I have an internal private domain that uses ULA's, I want the router assignment to have the 'M', 'O' and 'A' bits set and *NOT* act as a DHCP server (I want to tell my internal hosts to configure their global address using the router prefix *and* to consult my internal DHCP6 server to get an internal ULA). I have my own internal DHCP6 server that will serve up the ULA addresses (and provide DDNS services for the assigned addresses to my internal DNS server), but I cannot use it reliably when I set the 'M' bit to '1' because that also turns the ASUS into a competing DHCP6 server.

I have gone so far as to SSH into the ASUS unit and poke around looking for settings that I can manually tweak to configure the RA's, but I am not finding anything useful yet. There are a horde of variables in NVRAM, but it is not clear how or even if any of them are used in the construction of the RA's. I found one NVRAM variable called ipv6_radvd which is set to '1' which got my hopes up because I thought perhaps there would be a radvd.conf file that I could customize, but I cannot find such a file anywhere on the ASUS. There are also a large number of "ipv61_XXX" variables but I have no idea what "ipv61" stands for.

So has anyone else been able to fully configure their RA's from the RT-AC88U? If so, how? Failing that, if anyone has any information on whether there is a RADVD running on the ASUS and how to configure it, that would be helpful also.
 

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