Section 2.1.c (ii) VLAN Database The vlan database is what holds all VLAN and some VTP configuration. This database is stored as the file vlan.dat in NVRAM/flash. Since vlan information is not entirely saved in the running or startup config, an erase of these configs will not remove vlans from the switch. One would need …
2.1.c (i) Access Ports
Section 2.1.c (i) Access Ports Access ports are used to configure end devices where we want to restrict their membership to a certain vlan. They are called access ports because they are mainly used in the access layer. If an access port receives a frame with a .1q header, it will drop it. What are …
2.1.c Implement and Troubleshoot VLAN
Section 2.1.c Implement and Troubleshoot VLAN We cannot discuss VLANs until we learn the dot1q tag in depth. The dot1q header comes before the ethertype field in ethernet. It is a 4 byte value used to denote these 3 fields: 802.1P (class of service/layer 2 qos) DEI: Drop eligible indicator ID: vlan membership
2.1.b (i) UDLD
Section 2.1.b (i) UDLD Unidirectional Link Detection is a Cisco Proprietary protocol used to detect issues with links that utilize separate cables (fiber). UDLD can be enabled and becomes active when it detects a neighbor from the other side (both sides must be configured) Thus UDLD can only successfully work when configured on both …
2.1.b (i) CDP, LLDP
Section 2.1.b (i) CDP, LLDP CDP: We will start this discussion with the Cisco Discovery Protocol (CDP), a proprietary protocol invented by Cisco for finding directly connected device information. CDP is encapsulated in 802.3 Ethernet not Ethernet II. This feature is enabled by default and transmits every 60 seconds with a hold/expire time of …
2.1.b Implement and Troubleshoot Layer 2 Protocols
Section 2.1.b Implement and Troubleshoot Layer 2 Protocols One thing I wanted to discuss in this section is Ethernet, and all of the forms it may take. When looking at wireshark captures, we may notice the Ethernet headers as “Ethernet II”. This is the most common Ethernet protocol we use today. The above screenshot …
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