MikroTik behind a Fitz!Box

RouterOS Beginner Basics
1

Hello,

I have an ipv4 setup with a Fritz!Box that does NAT, and a MikroTik behind it that supports vlan, firewall etc. So everything is well connected.

My Fritz!Box receives a /56 prefix length ipv6, however, when adding a DHCPv6 client on MikroTik, it keeps saying that it is searching.

/ipv6 dhcp-client add interface=ether1 pool-name=IPv6-local-pool add-default-route=yes use-peer-dns=yes request=prefix

I would need to setup some kind of mechanism for the dynamic ipv6, DS-lite, I have from my ISP. There are various Fritz!Box options regarding DHCPv6 server or SLAAC, but I am unsure what to use, and my fiddling around did not help at all.

I do not know how to debug this, anyone has an idea? Also ChatGPT seems to be very hallucinating regarding this topic…

2

You should investigate if DHCPv6 server on Fritz is actually capable of passing out prefixes. I'd guess that typical end-user CPE (which Fritz essentially is) might not be capable of doing it. (you may set "request=prefix,address" to see if your MT can get at least IPv6 address from Fritz).
If you want to support multiple subnets (VLANs if you wish), then Fritz would need to support handing out shorter prefixes (e.g. /60 ... to support 16 /64 subnets). Which it might not (it's a non-trivial thing to do on ROS as well).

Additionally: don't set "add-default-route=yes" on MT's DHCPv6 client. It's a cludge and might not work properly in certain cases. DHCPv6 protocol doesn't actually support setting gateway address, the MT's cliedge instead takes DHCPv6 server address and sets it as default gateway. Which may not be correct. IPv6 instead offers mechanizm Routing Advertisements (RAs), which carry gateway information and should be used.

It might be easier to put Fritz into "transparent mode" (if you need Fritz for some particular reason, e.g. to act as xDSL modem or POTS gateway or ...) and configure MT to do the communication towards ISP directly. This way you'd avoid one layer of NAT for IPv4 and get possibility of doing IPv6 in an easy way.

3

It might be easier to put Fritz into "transparent mode"

This is true. Unless there’s a specific reason keeping double NAT, have an open firewall and verbose dns logs.

4

I have set this on my Fritz!Box:

image
image800Ă—517 79.9 KB

Its a FritzBox 7412, I cant find a bridge-mode setting…

5

Why do you need to use the Fritz!box? Perhaps if we knew that, we could start by working out the best configuration.

6

There’s no “transparent mode” on newer UNBRANDED ones.
Only exposed host.

Branded models might be different

Since we're talking about DS-Lite I'm assuming OP is using the Fritzbox as a DSL Modem.

Edit i just saw the 7412 which is a special case in this territory.
Anything newer than FritzOS 6.83 wont work as a Bridge Modem

7

Can Mikrotik do DS-Lite?

8

Yes.
Its also called IPIP-Tunnel

9

check here:

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