After the connection between two switches could not be established I went to see the log of the uplink switch and the first thing I have noticed was this: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up %SPANTREE-7-RECV_1Q_NON_TRUNK: Received 802.1Q BPDU on non trunk FastEthernet0/1 VLAN300. %SPANTREE-7-BLOCK_PORT_TYPE: Blocking FastEthernet0/1 on VLAN0300. Inconsistent port type. The two switches were connected via access ports and this message was on my side, since the other side was the service provider and I was not given the technical details of "the other side". [wp_ad_camp_1]   In short, interface was receiving BPDU's which weren't supposed to be there. This was the interface configuration: interface FastEthernet0/1 description UPLINK switchport access vlan 300 switchport mode access spanning-tree portfast…
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