Solved RT-AX68U Pro trying to reserve IP address my results

[Tech9]

I think you are confusing manually assigned (i.e. reserved) DHCP addresses with a statically defined address on the client.

Paraphrasing Eric's advice here... This remains my practice.

No, I tested it with static IP devices and the default DHCP pool. Asuswrt finds whatever IP is taken already and doesn't duplicate the IPs. In case the static IP device shows up later on the network the IP conflict will be resolved on the next DHCP lease or on reboot. I know what you guys are saying and it is correct, but in this specific home router case it works even if the user doesn't know about it and uses the defaults. It also works in a similar user-friendly way on TP-Link routers. We all know how to di it properly first time, but apparently this is not expected from an average home user. Not sure if Dnsmasq is doing it by itself or something else is helping in the process.

 

[OzarkEdge]

Still, it might be advisable to stick with a more universal, failsafe practice.

OE

 

[ColinTaylor]

Asuswrt finds whatever IP is taken already and doesn't duplicate the IPs.

dnsmasq doesn't have the ability to "find" anything that's been statically set on a client. The only scenario where dnsmasq would not offer a reserved IP address is if it knows that it has already given that address to a client.

 

[Tech9]

The only scenario where dnsmasq would not offer a reserved IP address is if it knows that it has already given that address to a client.

Perhaps this is how it works plus the chance 1:254 to offer the same IP. If IP conflict happens a reboot fixes it. I use static IPs outside of the DHCP pool like everyone else in this thread, but wanted to see what happens if the user has no idea how it works. Worst case they have to reboot and Dnsmasq takes care of things offering the same IP to the same MAC. I actually don't know why people waste time to assign IPs when they rarely change after DHCP auto assignment, if ever. Perhaps some like to see devices in some type of specific order in client list.

 

[bbunge]

I actually don't know why people waste time to assign IPs when they rarely change after DHCP auto assignment, if ever.

Rarely change? With the several recent Asus, and Merlin, firmwares I have had DHCP clients get different IP addresses after a firmware reset or change from Asus to Merlin and back. Often the change is one or two IP addresses higher or lower but it was a change none the less. And that is why static IP addresses are good for things like printers, NAS and other clients/servers that rely on "fixed" addresses (not fixed like the cat).

 

[dave14305]

The dhcp leases from dnsmasq should remain stable per client as long as the client MAC address, and the start and end of the lease range stay the same. It even will try to ping the address before issuing it.

asuswrt-merlin.ng/release/src/router/dnsmasq/src/dhcp.c at 6fc90ba530f1f3cb78fd72d8e6e52a8742e1f44f · RMerl/asuswrt-merlin.ng

Third party firmware for Asus routers (newer codebase) - RMerl/asuswrt-merlin.ng

github.com

 

[Tech9]

Rarely change?

Very rarely and because the default DHCP lease time is relatively long you can actually see a situation where you reset the router, change the firmware if you want, and when you boot it up the clients are still holding the same IP addresses. Again - I know what everyone is saying and why, I know it's the right advice in general, but static IP inside DHCP works okay in Asuswrt and not critical. Add relatively large IP pool for a home network and real issues are unlikely. In case IP conflict happens it fixes itself on DHCP renew or after reboot.

Seems like things are made easier these days. I found my UniFi gateway on IP conflict sends me a notification and by the time I open the Control Panel I find it fixed already. It just reconnects the auto IP assigned conflicting client and the life goes on with no drama. Perhaps useful when the network has 1000+ clients. This type of IP conflict may happen only if fixed IP device is connecting to a life system. UniFi OS has something called "Conflict Detection" and pings the devices before leasing an IP address. Asuswrt may have something similar.

 

[jksmurf]

I actually don't know why people waste time to assign IPs when they rarely change after DHCP auto assignment, if ever. Perhaps some like to see devices in some type of specific order in client list.

Yup that’s me, I like to assign them for two reasons; naming them and grouping them by sets of the last three numbers (octets?) eg series 192.168.x.120-129; 130-139 (10 device types), 140-159 (up to 20 device types) etc. Personal preference.

 

[Tech9]

Understood, personal preference indeed, but Asuswrt client list is quite inaccurate and that perhaps adds to the OCD.