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gsauthof
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Mikrotik Switch breaking IPv6 SLAAC

Sat May 29, 2021 10:35 pm

So, I've connected a Mikrotik CRS326 Switch to a FritzBox router which has IPv6 properly set up.

Thus, the FritzBox acts as an IPv6 router.

The problem I have now is that SLAAC doesn't work for hosts that are connected to the Mikrotik CRS326.

In contrast, if I directly connect one of those hosts to the FritzBOX then SLAAC works.

If I replace the Mikrotik CRS326 with a managed Netgear switch then SLAAC works, as well (i.e. for the hosts that are then connected to that Netgear Switch).

Thus, it seems that the Mikrotik CRS326 somehow messes with IPv6 multicast and/or ICMPv6 which is required for SLAAC.

Is there some RouterOS configuration setting to tweak such that the Mikrotik switch just forwards (on layer 2) the IPv6 SLAAC packets?

Additional information: the CRS326 has pretty much default settings, i.e. RouterOS installed (updated to latest stable, though), all ports are part of the one default bridge/switch. There are 2 VLANs (configured via '/interface bridge' and vlan-filtering is enabled) and the FritzBox is connected to an untagged port.
 
gsauthof
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Re: Mikrotik Switch breaking IPv6 SLAAC

Sat May 29, 2021 11:32 pm

Discovered that there is a separate IPv6 RouterOS package which is disabled, by default.

I thus enabled it like this:
/system package enable ipv6
/system reboot
With that change, SLAAC then works for hosts connected to the Mikrotik CRS326 switch.

I'm not sure why it didn't work out-of-the box. I mean, shouldn't the Mikrotik switch just l2-forward the IPv6 SLAAC packets like a dumb switch?

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