RP-AC55 Access Point handed out IP addresses?

[sfatula]

I have a pair of RP-AC55 devices functioning as access points on different sides of my long but skinny house. They have ethernet backhaul to an RT-AC5300. So, my router was offline for a bit and unreachable, moving stuff around. In the meantime, the access points were still plugged in and powered.

Once I plugged the 5300 back in, and, power returned, I found half the WIRED devices on my network non functional or reachable. Further investigation showed they had IP addresses different than the 5300 assigns them, and, their router was pointing to one of the access points, as well as their dns!

I thought access point disabled any ability of the RP-AC55's to hand out anything, how in the world could that happen? Any ideas? What am I misunderstanding? They all work fine normally, but this was very surprising and a total mess to find all the devices, power them off, and power back on one by one.

 

[KsWoodsMan]

yup , nature of the beast when the RP-AC55 can't connect to anywhere.

It wouldn't be so bad if the dnsmasq instance in them only gave 60 second dhcp allocations. The released them when it's connection came back up.
Or , maybe better yet , none at all so the clients continued looking for a dhcp server.

Dnsmasq is in there for those few times it is acting as a WiFi Proxy to connect to somewhere and yet hide the devices connecting through it.
Also to aid initial configuration when the owner connects by ethernet to set it up for their network.

I haven't played with mine in AI-Mesh mode, yet. The newest firmware now supports it for them as nodes.

 

[KsWoodsMan]

I thought access point disabled any ability of the RP-AC55's to hand out anything, how in the world could that happen?

I'm pretty sure it was a "race" from the time the switch in the 5300 started working till when it started giving out IP's with RP-55's already handing them out before deciding they had a connection of their own and stopped giving out "Wan down" IP's to the wired devices.

I don't know if enabling the WiFi Proxy mode on them then turning off the DHCP server would be "sticky" after setting them back to access points. Might be something to try, to stop this behavior when acting solely as access points.

 

[sfatula]

yup , nature of the beast when the RP-AC55 can't connect to anywhere.

It wouldn't be so bad if the dnsmasq instance in them only gave 60 second dhcp allocations. The released them when it's connection came back up.
Or , maybe better yet , none at all so the clients continued looking for a dhcp server.

So.... it sounds likely then that when we lose power, as happens from time to time, and power comes back, it's likely to encounter the problem. And if I'm out of town, all the worse as I need to access certain things at times.

I suppose the only workaround is to hard assign addresses on each device, where possible. Unless one had a device that could delay power on for the RP-AC55's.

 

[KsWoodsMan]

Unless one had a device that could delay power on for the RP-AC55's.

Or maintained power to the RT-AC5300 and gateway during the blackout with a UPS.

When the firmware for AI-Mesh 2.0 becomes available for them the wired nodes are supposed to stop this.
In the meanwhile I was curious about this on mine. So I tried a few things.
I was poking around in the nvram settings and found something that might help.

After logging in to mine remotely I looked over the nvram settings for a delay or wait and wasn't sure I wanted to play with any ATE statements there . But I did find dhcp_enable_x was set to 1.
Changing that setting from "1" to "0" stopped my RP-AC55 from handing out IP addresses when it couldn't find a connection to the outside world.

This also means when you try to connect to it without an internet connection it will revert to its default IP address of 192.168.1.1 or the unique value you've set in the GUI under LAN settings and it won't give you an IP address to connect to it. If, in the GUI, it is set to DHCP this value for it's LAN IP will be greyed out. To access it directly you'll need to manually configure the lan port of your conputer to the same IP range and subnet as the repeater. It would also help to have the ASUS Discovery app installed on your computer to find the repeater.

On mine with, current 384 firmware, telnet and ssh were both available.
I disconnected the lan cable to my RP-AC55 and connected instead to my desktop computer.
Then plugged in the repeater to AC power.
Soon after the repeater booted up, my desktop showed it had a valid IP address pointing it towards the repeater for configuration purposes.
I logged in via ssh . I gave the command nvram show | sort | less and it filled the screen with its settings sorted alphabetically making them easier to peruse.
I found the setting dhcp_enable_x=1 and made a note of it. I finished looking over other settings (wondering if I can add a guest account to this).
Exit from less by hitting "q" . Then issued nvram set dhcp_enable_x=0 ; nvram commit && reboot . To which it willingly obliged my commands.
In less than a minute it had rebooted but was no longer offering dhcp allocations for requests. The service dnsmasq is still running. But there is no config file. Without it, the repeater isn't replying to dhcp requests.
Resetting the AP to factory defaults either with the reset button or through the GUI should restore the dhcp function in case you need it for configuration purposes in the future.

Cheers !! and enjoy.

 

[KsWoodsMan]

Without it, the repeater isn't replying to dhcp requests.

A couple of other things it doesn't do now. The repeater isn't reporting to the main router what it's lan hostname is or how many clients are connecting through it. Devices that used to show up in the Network Map aren't there now and the repeater isn't identified as an RP-AC55 anylonger. Just by it's MAC address and the local IP address.
But , it's not giving out IP addresses while it thinks the WAN is down.
It also doesn't give out IP addresses now when set to WiFiProxy in Repeater mode.

One work around for this might be to set dhcp_enable_x back to "1" and change the lease time that it gives from 86400 seconds to less than 60 seconds. Your other devices would get an IP address from the RP-AC55 initially. But only for 30 - 60 seconds.
Of course, if it was ever used as a repeater with WiFiProxy enabled the clients would be banging away at it every 30 - 60 seconds to renew their lease.

 

[sfatula]

Yeah, I forgot I could even access the repeaters via ssh. For some dumb reason was thinking I only had the GUI without Merlin loaded, never used a generic ASUS before, lol. Lease time sounds like the better solution, assuming it works and is persistent.

The main router is on a UPS, that is taken care of, however, for longer power outages, it simply won't keep up. Also, my OP was a case where I simply took the router down to work on something, during that downtime, the RPs gave out addresses. So, a different case where a UPS doesn't help. Heck, even if the router simply needed rebooting I could "lose" devices. This a better solution was needed.

While I don't have time to test and am out of town anyway, I can vpn in and at least change the lease time and poke around a bit. Maybe it will prevent a disaster while out of town. Likely I won;t know for sure until the next power outage or extended router downtime. That could be a while, so, hard assigning IPs is on the table as a permanent fix should everything else fail.

Thanks for thinking about this, I clearly did not!

 

[KsWoodsMan]

Thanks for thinking about this ...

You are Welcome.

Possibly instead of fighting that behavior from them, you might embrace it and also hand set your static IP's up in the repeaters, with a short lease time. So the next time things go down or are brought down , they will happily give out short leases correctly till the authoritative DHCP server was back on line.
Once they realize a connection is available they should switch this off, handing over everything to the authoritative server.on your RT-G5300 .

Just a thought.

 

[sfatula]

When functioning as an access point, there is no screen to enter the 40 or 50 static ips in either RP-AC55. Would be simpler to just make them all static at the device level most likely than maintaining them in 3 places.

 

[KsWoodsMan]

When functioning as an access point, there is no screen to enter the 40 or 50 static ips in either RP-AC55. Would be simpler to just make them all static at the device level most likely than maintaining them in 3 places.

It is there . It just isn't advertized .

http://repeater.asus.com/Advanced_DHCP_Content.asp

40-50 places versus 3 places.
I would most definitely go with the 3 places.
or just 1 and migrate those settings to 2 more places.

 

[KsWoodsMan]

If you wanted to make it easier you could tranfer the output of the nvram get dhcp_staticlist from your main router to each of your repeaters and enable dhcp_static on them as well.

If you aren't comfortable working at a command line or mucking about with your nvram settings by hand then I wouldn't.
And probable best to use the link given to the Easter Egg above to do it.

For long lists with spaces or redirects be sure to encapsulate the value inside quotation marks .

dhcp_staticlist="<aa:bb:cc:dd:ee:ff>192.168.60.240>192.168.60.1<12:34:56:78:90:ab>192.168.60.1>"

 

[sfatula]

No, I know I can transfer manually the list. I just think the advantage of DHCP management is lost. I am sure I could script it too, and transfer every so often, etc. OR, I could just assign IP addresses on the devices and be done forever and spend less time. At least until if or when ipv6 some decade. But that's likely a subset of devices anyway. I will wait and see if I ever have any trouble first, I see little downside to 60 seconds or even a couple of minute lease times, so, I am hoping that just works and I don't have to do anything. I have enough work to do on drivers for home theater.

Again, thanks for your pondering of this situation and Happy New Year!

 

[KsWoodsMan]

You are welcome.
It wasn't a problem for me to try breaking mine. Then noting the results here in hopes you (or someone later found this and) benefited from it, also.

Glad Tidings and Happy New Year .

 

[chichow]

"When the firmware for AI-Mesh 2.0 becomes available for them the wired nodes are supposed to stop this."

You have faith that AI Mesh 2.0 will make it to the RP-AC55?