I know its a bit deep into the topics here, but I wanted a clear demonstration of what I mean when I say 3-Layer switch model, also known as the "hierarchical" switching model. Core Layer - Considered to be the "backbone" layer or "center" of a network, no routing or packet manipulation is done at … Continue reading A quick show of the 3-Layer switch model I have and will be referring to, if it’s been awhile since you’ve looked at Switching!
I found the most ancient Cisco phone model ebay had to offer for my lab, the old but reliable 7940, plugged just to the right of it on SW1 in port Fa1/0/24! Quick review of Voice terminology and definitions I'm going to dive just a bit into Voice terminology here at first, as the word … Continue reading Voice VLANs – Fundamentals, 4 types of Voice VLAN / traffic tagging config, verification commands, and a debug to finish!
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!
I wasn't sure what to put as a graphic here, so I thought a glimpse into troubleshooting hell would suffice, I dig the whole "chaos" theme of a million cables between devices 🙂 First I want to start with a couple things I previously had missed in prior articles: If you want to see only … Continue reading Dynamic VLANs, explained but no configuration, as config is not needed for SWITCH, the ups and down of using it!
That's right, we've gotten back to my crappy Paint topologies, as we all have come to know and love them. So given I don't have laptops around that I can piece into this home lab, I will be using a couple of my NBMA routers (2600XM series) as hosts C and D, while hosts A … Continue reading Configuring two broadcast domains, but creating one big problem, and some real world info!
This is the most basic VLAN graphic you could possibly find, it looks almost from the old CCNA v1 exam, however it perfectly illustrates the functions of VLANs! Just as ports on a switch break up "collision domains," VLANs break up "broadcast domains," which is not only required for traffic separation but also broadcast traffic … Continue reading VLANS: Static VLAN need to knows, configuration, verification, and troubleshooting on the CLI!
Power Over Ethernet in action on a phone so old it should have a rotary! One real world tip to start this off for finding a port # for a device like a phone, when things are mislabeled, and no one in the office knows what a switch even is and your troubleshooting remotely. If … Continue reading PoE Part 2 – Admin states explained exhaustively, with a lot of real world on the job info you might run into!
*The image above is courtesy / cited by air-stream.org, so thanks to you guys! This particular demonstration appears to be using an STP cable (Shielded Twisted Pair), however there are other alternatives that can be used, including foils and types of screens to keep the low voltage (hopefully) working properly. As we know from CCNA, … Continue reading PoE Part 1 – The fundamentals with a dip into some more complex topics, and PoE working in action and explained exhaustively!
So to begin with Port Speeds and Duplexing and configuring ports manually for full / half duplexing and speeds - Just don't do it. I say that first, because now, I am going to say why you don't want to do it. With Autonegotiation configured on two ports, they will send what is called FLP's … Continue reading Adjusting Port Speeds, Duplexing, and Autonegotiation – Don’t do it!