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frittentheke
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How to use fe80::1 (IPv6 Link-Local) via VRRP to provide redundant default GW?

Wed Feb 28, 2024 11:13 am

It's somewhat common to use fe80::1 as link-local address to provide default gateway functionality to a segment.
So I wanted to configure this on a routers interface as (an additional) link-local address.
Apparently this does not work on Mikrotik / RouterOS (7.13):

1) Neither as native link-local address on an interface:
/ipv6/address/add address=fe80::1/64 interface=myinterface advertise=no
failure: can not add link local address

2) or as VRRP floating IPv6 addresss
/ipv6/address/add address=fe80::1/128 interface=myinterface-vrrp advertise=no
failure: can not add link local address


Is there any way to achieve this?
 
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eworm
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Re: How to use fe80::1 (IPv6 Link-Local) via VRRP to provide redundant default GW?

Wed Feb 28, 2024 11:16 am

I think you should use ULA (Unique Local Address) for this...
https://en.wikipedia.org/wiki/Unique_local_address
 
frittentheke
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Re: How to use fe80::1 (IPv6 Link-Local) via VRRP to provide redundant default GW?

Wed Feb 28, 2024 11:38 am

I think you should use ULA (Unique Local Address) for this...
https://en.wikipedia.org/wiki/Unique_local_address
No, they serve a different purpose. ULAs are routable addresses and thus cannot be the same for multiple segments, like link-locals can.
I have plenty global unicast addresses. But I explicitly want to achieve a uniform default gateway address.

Actually that IPv6 address is only used to find the MAC address of the segment router, nothing more.
IPv6 ND is used to determine which MAC address to send any non-local traffic to. So having a link-local address serve this purpose makes sense.
 
frittentheke
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Posts: 45
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Re: How to use fe80::1 (IPv6 Link-Local) via VRRP to provide redundant default GW?

Wed Feb 28, 2024 11:42 am

There was a similar question on Reddit a while back: https://www.reddit.com/r/ipv6/comments/ ... _mikrotik/

This approach is e.g. used by the Hoster Hetzner:
* https://docs.hetzner.com/cloud/servers/ ... tion/#ifup

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