Next to the proposed faults of:
- remove secondary IP
- change subnetmask on R5
There are two other mistakes as well:
- Loopback interfaces on SW3-4 are identical to SW1-2
- Vlan 89 has wrong IP-subnet according to diagram. In Sol Guide it mentions 89.0/24 again, so something's off here.
Not so good for troubleshooting...I should receive 4 points in the lab for this! ;-)