Hello. After 6.42.1 (Current) is installed on the Cloud Hosted Router, the VM starts periodically to be unavailable through the network interfaces, the error is preceded by a message in the dhcp, critical, error :: dhcp-client on WAN lost IP address XX.XX.XX.XX - lease expired.

Does anyone know the solution to this problem?

We're experiencing same issue. Loging to console and rebooting through ALT+CTRL+DEL (everything reboots perfectly – no freezes or problems) fixes problem temporary.
Also check same problem on different thread:
viewtopic.php?t=133716

We're experiencing a similar issue on Hyper-V, albeit without the DHCP component.

We're using CHR routers to front customer cloud environments, to route public and private traffic. Periodically these routers are deciding that the private interfaces aren't working; The symptom being that the next-hops associated with these interfaces are marked as unavailable when they are online. Restarting the CHR router magically resolves the issue. This has only started since the 6.42.1 update, would advise against upgrading in your on Hyper-V.

Don't forget to inform support by email. Otherwise nothing will happen...

I did, no reply after week and a half, so there you go, everyone is silent about this botched build

This issue has been resolved in 6.43rc: viewtopic.php?f=21&t=133420&start=50#p660193
(Specifically the issue mentioned in opening post)

Version 6.43rc7 has been released.

Changes since previous rc release:

*) capsman - allow to change "radio-name" (CLI only);
*) dhcpv4 - prevent sending out ICMP port unreachable packets;
*) dhvpv4-client - fixed DHCP client stuck in renewing state;
*) kidcontrol - allow to edit discovered devices;
*) lte - do not allow to send "at-chat" commands for configless modems;

A workaround is to downgrade to 6.40.8 or add a dhcp renew script (dhcp unicast fails, force renewal will fallback to dhcp broadcast sooner - before release):


Tune the interval to renew as late as possible but a few minutes before regular dhcp lease timeout.

RouterOS version 6.43rc23 just have been released. It involves CHR related fixes that might resolve problems mentioned within this topic.