Symptoms:
After upgrading from 7.22 to 7.23, WAN connectivity broke. Sequence of troubleshooting:
DHCP client on ether1 initially stuck on "searching"
After a manual second reboot, DHCP client showed "bound"
Shortly after, it started flapping repeatedly between "bound" and "searching"
Ethernet link (R flag) on ether1 stayed up/stable throughout
Config (WAN in interface list, NAT masquerade rule, bridge ports) all correct and unchanged
When DHCP client did show "bound": dynamic default route (0.0.0.0/0, DAd) was present with a gateway address
Pinging the gateway IP itself resulted in "destination host unreachable"
ARP table entry for the gateway showed status "incomplete" (no ARP replies received)
No relevant DHCP or link/interface errors found in the log at the moments of the drop
Full cold power-cycle of modem (60+ sec unplugged, cable modem in bridge mode) did not resolve it
Test: connected a laptop directly to the modem, bypassing the router entirely — also failed to get a working connection
Conclusion so far: Since the laptop directly on the modem also failed, this currently points to a modem/ISP-side issue rather than a RouterOS 7.23 bug — but the timing right after the upgrade (7.22 → 7.23, no config changes made) was suspicious enough that I wanted to check if others have seen this.
Question: Has anyone seen ARP/gateway-unreachable behavior like this specifically tied to 7.23 with cable ISPs in bridge mode, or is this most likely unrelated to the RouterOS upgrade?
Also rolling back RouterOS and used packages to 7.22.2 resolved it.
I cannot tell you which 7.23 patch version it was since i kind of rushed to get back online with working from home being a necessity, and some weeks passed since i tried the update.
In ROS 7.23, there is a change whereby, in the default configuration, IPv6 RA packets are also sent to the WAN interface. This can confuse the modem, causing it to stop the service.
In ROS 7.24, MT has implemented a workaround here; however, this requires manual intervention to get IPv6 working again.
No, you only need to upgrade to something >= 7.23.3. Current long term is 7.23.7 and current stable is 7.24.4, so both are ok. WARNING: RouterOS 7 versions <= 7.23.3 and 7.24-7.24.1 have security vulnerabilities and should not be used.
If you upgrade from 7.22.2 to 7.23.7 or 7.24.4 then you don't need to make any configuration change. The router will be in a backward compatible workaround mode with the behavior from 7.22 and below.
But if you decide to make setting changes under /ipv6 nd then be aware of the new behavior that will then applies. See:
Yes, I would disable the entry for ‘all’ and create (copy) a new entry for each of the required interfaces or bridge. @CGGXANNX has already commented on the firmware.
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