Link local address PPPoE WAN interface and Link local LAN adddress

[staticznld]

Hi,

It looks like the link local address of the WAN PPPoE is the same as the link local address of the LAN interface.

Code Select Expand

igb2: flags=8a43<UP,BROADCAST,RUNNING,ALLMULTI,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=802028<VLAN_MTU,JUMBO_MTU,WOL_MAGIC>
ether 40:62:31:02:cb:19
inet6 fe80::4262:31ff:fe02:cb19%igb2 prefixlen 64 scopeid 0x3
inet6 2a02:a450:839:XXXX:XXXX:XXXX:fe02:cb19 prefixlen 64
inet 172.19.0.1 netmask 0xffffff00 broadcast 172.19.0.255
media: Ethernet autoselect (1000baseT <full-duplex>)
status: active
nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>

pppoe0: flags=88d1<UP,POINTOPOINT,RUNNING,NOARP,SIMPLEX,MULTICAST> metric 0 mtu 1500
inet6 fe80::4262:31ff:fe02:cb17%pppoe0 prefixlen 64 scopeid 0xf
inet6 fe80::4262:31ff:fe02:cb19%pppoe0 prefixlen 64 scopeid 0xf
inet 77.XXX.XXX.91 --> 195.190.228.50 netmask 0xffffffff

There are no troubles using IPv6 connectivity on the IGB2 LAN network.
From the LAN side i am unable to ping the link local address of the router!
Running a traceroute from a client to google reports the GUA address as the first hop.

Anyone capable of explaining this behaviour?

[franco]

pppoe0 runs on top of igb2?

Link local addresses are unique to their interface (scope) and can overlap between interfaces without an issue. I suspect if the above is true the link-local gets cloned from the parent - maybe it shouldn't but that's for mpd5 software to decide/fix. The strangest thing seen here is that pppoe0 actually gets two link-local addresses and that doesn't make much sense as it only needs one.


Cheers,
Franco

[staticznld]

pppoe0 runs on top of IGB0!
Thats the strange thing!

So i suspected the link local address would be generated from the MAC address of IGB0 and not IGB2.

The pppoe tunnel is build over Vlan6 on IGB0

[franco]

> pppoe0 runs on top of IGB0!

> The pppoe tunnel is build over Vlan6 on IGB2

So which one is it? :)

[staticznld]

IGB0 sorry :-[

In Interfaces Overview WAN the fe80::4262:31ff:fe02:cb19/64 is used as link local.

[franco]

Ok, since addresses are just 2 digits apart and your NICS probably also have close addressing due to MAC address being close I think something just calculates from an offset and hits the other offset of the physical odering.

But as said the duplicated addresses are no problem going from scope to scope. Why it has 2 link-locals I do not know. I don't believe we are doing that.


Cheers,
Franco

[staticznld]

IGB0: 40:XX:XX:02:cb:17 WAN
IGB1: 40:XX:XX:02:cb:18 LAN currently unused
IGB2: 40:XX:XX:02:cb:19 GUEST
IGB3: 40:XX:XX:02:cb:1a unused
IGB4: 40:XX:XX:02:cb:1b unused
IGB5: 40:XX:XX:02:cb:1c LAN


Last night i moved my LAN from IGB1 to IGB5, the link local address on opnsense ends with CB:1C as expected.
I was also able to ping the link local address from the lan to opnsense.

From my guest network i am unable to ping opnsense through link local ending with CB:19.

Before is switched my LAN to IGB5 i had it on IGB1.
In this scenario is was unable to ping the link local address of opnsense.
The link local address was the same CB:18 address as link local of the PPPoE tunnel!

I am not having any problems with guest interface but found this behaviour strange.