Moving to Core 2,
well the console messages here sort of giveaway one of the problems,
stating that there's a duplicate address on gigabit 3.
Gigabit 3 has the 10.10 .10 .13 address on it.
With a 252 mask,
the 10.10 .10 .13 address would be on the 10.10 .10
.12 network so you would have 12, 13, 14,
and 15 on that subnet, and 13 and 14 would be the addresses,
and gigabit 03, well, that didn't work.
CDP must not be working on the other side,
but Core 1 and Core 3 are connected so it's none of those.
Let's go to Ral1 and see if that's it.
Well, I guess that must be it.
Ral1 still has the same console message from before and is also
configured with the 10.10 .10 .13 IP address.
So like I said, that's on the 12 network,
and the 13 and the 14 addresses are the valid network addresses on that subnet.
So if we change either side,
but we'll just change this side to the other address,
and see, that should make this reachable. And there's the network there.