hi
I have a problem with updating the arp table in clients suddenly and I couldn`t figure out what is the problem!

we have a 3011 router in the router with dhcp and hotspot enabled, suddenly I noticed some devices lost the internet connection! searching and find out that they cant ping the router because they didn`t have the mac address of the router! I check the router and saw all the MACs in the arp table of router so I think the router does not complete the arp request! after restarting the router all the clients lost the connection to the router! the only devices that work were the devices with static addresses! dhcp clients didnt have the mac of the router! the problem solved by itself after some time but it still is glitchy , and is not working as expected ! plus the web page of the hotspot enabled on the problematic bridge is unreachable on some devices! even after reconnecting to the the mikrotik! the router os version is 7.14.3 which is latest!
any idea what could be the problem?

Just an educated guess here. Since the clients with static IP addresses can reach the router, but DHCP clients can not, this sounds like an IP, not an arp issue. Go to one of the non working PCs and open a command prompt and execute: ipconfig /all Confirm that the computer received an IP address, and has a default gateway address (should be the router IP). Of course the default gateway is not needed to reach the router, but since they can't reach the Internet, it may be a clue. Next execute: arp -a See if the IP and MAC of the router appear in the list.

tnx for reply, they do have Ip addresses and all! actually the local traffic works fine! all the clients can communicate to each other just the mikrotik mac address does not exist in arp /a table of clients! although the mikrotik table is fine and it has all the clients mac addresses!

I also use a MikroTik 3011 and have experienced a similar issue with my Apple TV, which couldn't access any external network resources. Initially, the problem resolved itself but then reoccurred. I found that manually removing the IP from the ARP table immediately restored connectivity. Upon checking my DHCP server settings, I noticed that "Add ARP for Leases" was enabled. I suspect this setting might be the root of the problem, so I have now turned it off. Let's see if this resolves the issue permanently.

In case of Apple TV, could be issue with combination of DHCP setting "Add ARP for Leases" and Apple TV Wi-Fi privacy (Wifi MAC randomization).

In case of Apple TV, could be issue with combination of DHCP setting "Add ARP for Leases" and Apple TV Wi-Fi privacy (Wifi MAC randomization).

Good point. However, it turns out that my Apple TV does not have the Wi-Fi privacy feature as it is a model prior to the 4K version, which excludes the Wi-Fi MAC randomization capability. Thank you for highlighting this potential issue!

I found that manually removing the IP from the ARP table immediately restored connectivity. Upon checking my DHCP server settings, I noticed that "Add ARP for Leases" was enabled.

Playing with non-default ARP settings (both in DHCP server and bridge properties) is most often not necessary so it's best to avoid doing it if one doesn't know exactly what he's doing. It's a handy functionality in certain use cases ... but then I'd assume that one implementing the "certain use case config" knows how to use these features safely.

So I suggest you to set "add-arp=no" on DHCP server (default setting) and "arp=enabled" on bridge (if it's not left at default). This will allow bridge (switch chip) learn MAC addresses (per port) the normal way.

I also use a MikroTik 3011 and have experienced a similar issue with my Apple TV, which couldn't access any external network resources. Initially, the problem resolved itself but then reoccurred. I found that manually removing the IP from the ARP table immediately restored connectivity. Upon checking my DHCP server settings, I noticed that "Add ARP for Leases" was enabled. I suspect this setting might be the root of the problem, so I have now turned it off. Let's see if this resolves the issue permanently.

well my 3011 router was with the default dhcp settings and "add arp for leases" was disabled from the beginning! I tried to enable this but nothing happen! the problem is that somehow mikrotik mac does not exist in clients arp list! the mikrotik already has the mac of the devices! so when I ping router from the clients I get the error of "Destination host unreachable" because there is no arp record for the router IP! in that moment nothing solves the problem! replunging the ethernet cable, ping from router .....
I think ther is some kind of bug in routeros version 7! as I am an experienced network admin and there was no logical problem to solve this issue and the problem solved by itself!