Hi. I am playing with IPv6 gateway/routing and noticed a strange behaviour that I don’t understand.
This is my network configuration:
PC->eth->router1->eth->router2
PC:
Link-local IPv6 Address: fe80::9/64
Default Gateway: fe80::3
Router1 (RouterOS 6.49.10):
Link-local IPv6 Addres on bridge interface fe80::3/64
no other IPv6 settings (so IPv6->Routes table is empty)
Router2 (RouterOS 6.49.10):
Link-local IPv6 Addres on bridge interface fe80::1/64
Global IPv6 Address on bridge interface: 1234::1/64
I am able to ping 1234:1/64 (Router2) from my PC, but I am not able to ping that from Router1 (no route to host)
Why?
Since Router1 has no route to Router2, I would expect the ping to fail also from PC, since Router1 is used as gateway and PC has no IP with 1324::/64 prefix
Seems like it’s connected with Windows Neighbor cache on Windows. After clearing it, the router1 is not pingable anymore.
But I think the question still stays. Even when the router1 is cached on Windows PC, how can it be pingable from fe80::/64 interface, when it has to come through the gateway (Router2), from which it’s not pingable?
Export /ipv6 config from both routers. This is likely misconfig.
I have left out a few details.
At first, the router1 had a IP on 1234::/64 range (and thus also a pingable route to 1234::1.). While it had that IP, I tested ping from PC to router2 and that’s when the neighbour got cached on PC. Only then I disabled the IP on the router1. But since on the PC the IP+MAC of router2 is already cached, does it even need to use router1 as a gateway? Because obviously, in order for the ping packet to reach router2, physically the packet needs to come through the router1. But maybe it does not need to be “routed”, only “switched” and that’s why it works even when the IP+route is disabled on router1?
Anyway, the configs:
router1: empty (default)
router2:
/ipv6 address
add address=1234::1 interface=bridge1