Bug in ipv6 link-local address is now generated from tunnel local-address

RouterOS General
1

In Release 6.37 there was this improvement:
*) tunnel - ipv6 link-local address is now generated from tunnel local-address;
Now, using Release 6.38 I’ve found what I think is a bug:
Let’s create a 6to4 tunnel with local address 10.0.0.1 and show the associated ipv6 link-local address:

[admin@MikroTik]>interface 6to4 add local-address=10.0.0.1
[admin@MikroTik]>ipv6 address print
#       ADDRESSS         FROM INTERFACE      ADV
...
6 DL  fe80::a00:1/64          6to4-tunnel1    no

a00:1 is the hexadecimal representation of 10.0.0.1
Now, let’s create another 6to4 tunnel with local address 11.0.0.1 and show the associated ipv6 link-local addresses:

[admin@MikroTik]>interface 6to4 add local-address=11.0.0.1
[admin@MikroTik]>ipv6 address print
#       ADDRESSS         FROM INTERFACE      ADV
...
6 DL  fe80::a00:1/64          6to4-tunnel1    no
7 DL  fe80::a00:1/64          6to4-tunnel2    no

As you can see, it’s the same local link address. I think it should be fe80::b00:1/64 instead.
As far as I have tested, it seems that the auto-generated link-local address ignores the 8th bit of the IPv4 local-address.

Is this a bug or a feature?

6to4 - fixed wrong IPv6 "link-local" address generation , what does it means?
2

I can confirm this behaviour with latest 6.39rc27 and it does look like bug. At least I can’t come up with any good explanation what kind of feature it could be.

3

It’s intentional. It used to be generated from the tunnnel name so if you created a tunnel called sitea_siteb on both routers they would have the same ll address and ospfv3 wouldn’t work over them.

4

The complaint is that it ignores one bit from address, so you can still get same LL addresses for two different IP addresses.

5

Ahh. I see. Yeah. That looks like a bug.

6

Thank you very much for your opinions. Anybody knows how to report this bug? Or maybe Mikrotik read this forum and will solve it?

Thank you again!

7

support@mikrotik.com

8

Thank you very much for the report, it seems interesting. We will try to fix it shortly.

9

This issue has been fixed in version 6.39.2. I’ve tested it and seems it is working fine.

Thank you very much!