To demonstrate allowing and disallowing the VLANs across a Trunk I am re-configuring the above Topology, but I wanted to touch quickly on the management domain output from my previous tired ramblings. The management domain VLANs have to do with VTP (next topic to cover), and in the case I was looking at, it was … Continue reading VLAN Management Domains explained at Layer 2 and 3 (from end of previous post), TSHOOT / Real world on the job troubleshooting of VLAN issues!
The above topology is a good reason you may not want to allow all traffic over your Trunk ports, which will be explained below, as you may have guessed! (I did change the switch configs / cabling for this lab session to the above topology) Adjusting switch 2 properly with port moving and deleting VLANs: … Continue reading Filtering VLANs “Allowed on Trunk” on the CLI, discussing options and methods, and some real world info mixed in there!
The above Trunk modes in the Topology will be representative of SW1 only, as SW2 will remain with Trunk ports in their default mode of Dynamic Auto, to see the difference in debugs and verification output. Fundamental information for Exam day! DTP is what makes negotiation possible, handling the negotiation between the Trunk … Continue reading DTP (Dynamic Trunking Protocol) fundamentals, labbing / explanation of verification commands, some oddities, and some debugging!
And so the Elephant begins the Trunking negotiation with the humans face! First I will tackle both modes and encapsulation types using IOS help, review as I go along, and a quick summary to wrap up both Modes and Encapsulations: SW2(config-if)#switchport mode ? access Set trunking mode to ACCESS unconditionally dot1q-tunnel set trunking mode to … Continue reading Trunking Modes, Encapsulation Types, and Trunk behaviors DEEP DIVE on the lab, NEED TO KNOW info for exam day!
To kick start things off, I still have our respective host / trunk ports, but for security purposes we don't want to keep the "Native" VLAN as 1, because as was said in the last post any untagged traffic showing up at an 802.1q Trunk will be forwarded across it as though it came from … Continue reading The Native VLAN – Configuration, verification, error messages to know for exam day!
The above image seems to be courtesy of the Cisco Learning Network, so thank you Cisco Learning Network! "Frame Tagging" is adding a VLAN ID tag to an Ethernet Frame when traversing a Trunk, depending on what encapsulation you are using it has different rules, and one important note is that when a Frame traverses … Continue reading Using ISL vs Dot1q for Trunk encapsulation (Frame Tagging), along with the pro’s and con’s of each!
This will be the logical topology being created for R1 - R4 to communicate over Trunks! Some things to get out of the way right off out of the gate regarding Trunks: By default, a Trunk is in all VLANs, so it will allow ALL Data across its link (including Broadcasts that we want to … Continue reading Intro to VLAN and Trunk configuration, behaviors, and labbing output to demonstrate the setup!