spanning-tree instance. A bridge group establishes a spanning-tree instance based on the BPDUs it receives on only its member interfaces. This example shows configuring a Layer 3 port and an SVI, and combining them into the bridging process. Non-IP traffic will be bridged, and IP traffic will be routed.
Switch(config)# interface vlan2 Switch(config-if)# ip address 172.20.128.1 255.255.255.0 Switch(config-if)# exit
Switch(config)# interface gigabitethernet0/2 Switch(config-if)# switchport mode access Switch(config-if)# switchport access vlan 2 Switch(config-if)# no switchport Switch(config-if)# ip address 172.20.130.1 255.255.255.0 Switch(config-if)# no shutdown Switch(config-if)# bridge-group 10.24
UniDirectional Link Detection (UDLD)
UDLD is a Layer 2 protocol that enables devices connected through fiber-optic or twisted-pair Ethernet cables to monitor the physical configuration of the cables and detect when a unidirectional link exists. All connected devices must support UDLD for the protocol to successfully identify and disable unidirectional links. When UDLD detects a unidirectional link, it administratively shuts down the affected port and alerts you.
Unidirectional links can cause a variety of problems, including spanning-tree topology loops. UDLD works with the Layer 1 mechanisms to determine the physical status of a link. At Layer 1, auto negotiation takes care of physical signaling and fault detection. UDLD performs tasks that auto negotiation cannot perform, such as detecting the identities of neighbors and shutting down misconnected interfaces. When you enable both auto negotiation and UDLD, Layer 1 and Layer 2 detections work together to prevent physical and logical unidirectional connections and the malfunctioning of other
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