Overview: Cisco Discovery Protocol CDP is a Cisco proprietary layer 2 protocol to help switches learn about neighboring switches Study Notes: Cisco Discovery Protocol (CDP) Cisco Discovery Protocol is a Layer 2, media-independent, and network-independent protocol that networking applications use to learn about nearby, directly connected devices Cisco Discovery Protocol is enabled by default […]
Overview: The CCNA will test you on the following Layer 2 protocols: 2.8.a Cisco Discovery Protocol (CDP) 2.8.b Link Layer Discovery Protocol (LLDP) Links: If you’re not already inundated by information or you’re just ready for a break where you aren’t required to remember any details, you might find this article interesting. It’s about […]
Overview: BPDUGuard protects against loops that STP can’t protect against when PortFast is enabled Study Notes: BPDU Guard complements the functionality of PortFast On PortFast-enabled ports, BPDU Guard provides the protection against Layer 2 loops that STP cannot provide when STP PortFast is enabled In a valid configuration, PortFast Layer 2 LAN interfaces (edge ports) […]
Overview: PortFast is a Spanning-Tree option that causes a port to immediately come up without going through initial STP learning and listening phases Study Notes: STP PortFast causes a Layer 2 LAN port configured as an access port to enter the forwarding state immediately, bypassing the listening and learning states You can use PortFast on […]
Overview: The optional features of the Spanning Tree Protocol (STP) enhance loop prevention, protect against some possible user misconfigurations, and provide better control over the protocol parameters. Although similar functionality may be incorporated into the IEEE 802.1w Rapid Spanning Tree Protocol (RSTP) standard, we recommend using these extensions. With the exception of PVST Simulation, all […]
Overview: The first step in STP is the root bridge selection. From there all other STP decisions are made. Study Notes: The key to Spanning-Tree Protocol is that a root bridge must be selected to become the focal point in the network All STP decisions in the network are made from the point-of-view of […]
Overview: Per-VLAN Spanning-Tree plus and Rapid PVST+ are enhancements to 802.1D STP Study Notes: 802.1D Spanning Tree Protocol (STP) has a drawback of slow convergence Cisco Catalyst switches support three types of STPs, which are PVST+, rapid-PVST+ and MST. Per-VLAN Spanning-Tree plus (PVST+) PVST+ is based on IEEE802.1D standard and includes Cisco proprietary extensions such […]
Overview: Spanning-Tree Protocol prevents loops in a network Problems that Spanning-Tree Protocol fixes: Switches are interconnected with redundant links for resiliency, but that caused loops and broadcast storms Connecting switches like this also caused inconsistent MAC address tables because the switch would see the same host MAC address on two different ports If the switch […]
Overview: The Native VLAN is used to pass untagged traffic (non-vlan associated) to a neighboring switch Study Notes: Native VLAN: On a trunk link, each frame must be distinguishable as being within exactly one VLAN If a frame does not carry an 802.1Q VLAN tag, it is considered to be in the Native VLAN […]
Overview: 802.1Q is the standard used for switches to communicate Layer 2 VLAN information between each other Study Notes: 802.1Q 802.1Q, or dot1q for short, is a way to tag vlans on an Ethernet frame It is an open standard and more popularly used than Cisco’s proprietary VLAN encapsulation protocol called Inter-Switch Link (ISL) […]