Port Security Is used to limit access to a port based on MAC addresses. Can only be configured on static access or trunk ports. No dynamic links. By default, once a port goes into ERR-DISABLE it doesn’t come out unless: Shut/no
When troubleshooting ports and trunks, consider the following: Confirm the state of the ports: # sh int | i line If an port is UP/DOWN, is it caused by
IOS can route or bridge a protocol, not both. Defaults: Routers have IP routed. Switches have IP bridged. Transparent bridging is subject to normal STP rules. Only one active path. Root bridge election. Root port election. IRB and CRB are
CAM Table Maintenance Static Entries Could be useful to statically hard-code which MAC addresses are reachable via which ports. Another use is to Null-switch a MAC address. If the port is down, traffic to that MAC will still be dropped.
MSTP Overview MSTP is the IEEE 802.1S-2002 standard inspired from the Cisco proprietary MISTP (Multiple Instances Spanning-Tree Protocol). MSTP decouples the VLAN to spanning-tree instance relationship to allow VLAN-independent instances. The instances are administratively created with multiple VLANs assigned to
RSTP was originally defined in the IEEE 802.1w standard to provide significant faster convergence while still backwards compatible. RSTP was later incorporated as section 17 in IEEE 802.1D-2004 standard for STP. The remainder of this section will reflect on the
STP was designed to prevent bridging loops in layer2 networks, typically created by redundant paths. The initial IEEE 802.1Q standard specified the transport of BPDUs over a native VLAN, with no support to differentiate between BPDUs from different VLANs. Originally
EtherChannel is a LAG (Link Aggregation) technology that aggregates multiple physical ports, which is presented and used as a single logical Ethernet port. The goal of EtherChannel is to provide greater bandwidth and better redundancy than using a single port.
Layer3 Routed Ports Same as a regular Ethernet interface on a router. Configured with “no switchport” and “ip address”. Some switches do not support layer3 routed ports anymore, instead the creation of an SVI is required for layer3 routing. Router-on-a-Stick
Is used to advertise VLAN attributes and ease administration of VLANs across multiple switches. VTP is a management protocol and is not need to use VLANs. The VTP domain name is the basic configuration needed for a switch to be