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Dear YLs and OMs,
beware of the latest Mikrotik RouterOS version 6.21 and 6.22.
It generates strange IPIP packets adressed to the remote endpoint of an IPIP tunnel. The IPIP packets itself contains an IP packet that is addressed from the remote endpoint to the mikrotik router.
Pseudo packet capture
Frame: 1 Time: 0 Internet Protocol Version 4, Src: Mi.Kr.Ot.Ik (Mi.Kr.Ot.Ik), Dst: Re.Mo.Te.IP (Re.Mo.Te.IP) Internet Protocol Version 4, Src: Re.Mo.Te.IP (Re.Mo.Te.IP), Dst: Mi.Kr.Ot.Ik (Mi.Kr.Ot.Ik)
Frame: 2 Time: 10 Internet Protocol Version 4, Src: Mi.Kr.Ot.Ik (Mi.Kr.Ot.Ik), Dst: Re.Mo.Te.IP (Re.Mo.Te.IP) Internet Protocol Version 4, Src: Re.Mo.Te.IP (Re.Mo.Te.IP), Dst: Mi.Kr.Ot.Ik (Mi.Kr.Ot.Ik)
and so on, almost every 10 seconds.
Once I downgraded to version 6.20 the strange packets seem to have stopped appearing.
If someone discovers the origin of this issue and knows of a way to avoid the issue other than downgrading, please let me know.
Thanks to PE1CH for notifying me after seeing the strange IPIP packets on his system.
73 de Marc