We will be undergoing scheduled maintenance on May 20th, 2013 at 02:00 GMT.
Implementing Cisco IP Switched Networks (642-813 SWITCH) Tutorials
Switch and VLAN Basics / VLAN Trunking pt. 1
Subtitles of the Movie (Implementing Cisco IP Switched Networks (642-813 SWITCH) / Switch and VLAN Basics / VLAN Trunking pt. 1)
In this video we're going to talk about VLAN Trunking and VLAN Trunking is really a CCNA level topic for the most part. However, to make sure we're all on the same page with regards to the terminology and the technology involved, I'm going to go over VLAN Trunking and we'll also talk about a very common error you'll see when you're setting up VLAN Trunks. We'll talk about that in the very last slide. So in what situations would you use a VLAN Trunk? Well let's say you have a network that's kind of set up like this. You've got two switches and you've got three VLANs and you've got machines on both switches connected to each of these VLANs. For example, VLAN 50 you've got some computers on this switch and that switch and same with all three VLANs. So how does the traffic get between one switch to another? Well that's that purple link that you see right between the two switches and that is the VLAN Trunk. Now if you're coming from a non Cisco background, if you're working on 3Com or HP switches, I've got a customer of mine that uses HP switches. They don't call these Trunk Ports, they call them Tagged Ports which is kind of a more logical name for them in my opinion, because you're not really trunking anything, you're just tagging the packets as they go across this port and they're decoding the tags on the other end of the trunk. So that you can then split it out amongst all of the machines on that local switch. So what is the purpose of a VLAN Trunk? It is used to flood broadcast and multicast packets to all the Switch Ports on the same VLAN. Going back to our diagram up here, we'll go back a couple of slides. If I am sitting on this PC and I want to send a broadcast so that this machine over here gets it, well I'll send it over here, it'll go across this trunk, because this switch realizes, hey this is a broadcast, I need to flood it over to this other switch. And then it will take that broadcast and broadcast it to this other machine that's sitting on VLAN 50 on the other switch. Now there is a way to prevent this if you don't actually have any ports on that second switch that's in VLAN 50. It's called VTP Pruning and we'll talk about that a little bit when we talk about the VLAN Trunking Protocol. So how does it do it? How does Trunks work? Well the Trunk Ports basically prepend a VLAN ID to the front of the Ethernet Frame and it does that in a couple of different ways and we'll look at the layout of the packets here on the next couple of slides and you'll be able to see the difference in the two trunking mechanisms, the two trunking methods. Two types of trunking, there is the Inter-Switch Link, the ISL Trunk and this is a Cisco proprietary protocol. It's being phased out, so much so that the newer switches, you'll buy the 2960, the 2950, the 3500 and the 3600 series of switches, 3600's really a router but the newer switches that you'll buy, don't even have ISL as an option. Now when we get into my lab, I have an older switch, it's a 2900XL switch that I use just to demonstrate some of the features that are available or the lack of features that are available on the older hardware and software revisions. And you'll see on that switch we have an option for either an ISL or an 802.1Q Trunk. Whereas on the new switches, we only have a .1Q type of trunk or actually it doesn't even give us the option at all, but we'll, we'll talk about that when we get into the lab. The ISL Trunking was created before the IEEE formalized the 802.1Q VLAN Tags and ISL works by basically encapsulating the packet and we'll get into that on the next slide when we look at the packet layout for an ISL packet. The other type of trunk is 802.1Q VLAN Tagging, this is industry standard, you can take a Cisco switch and hook it up to an HP switch and send 802.1Q VLAN Tags across Trunk Ports and the HP switch will understand what the Cisco switch is speaking. It's supported by all the modern switches, if you bought a switch in the last 6 or 7 years, in fact I've seen some switches as old as 10 years old, support 802.1Q VLAN Tagging. 802.1Q basically just inserts a priority and a VLAN ID in the Ethernet Header, it doesn't re-encapsulate the entire frame. So it's a lot less overhead on the switches because these switches don't have to constantly add and take away these headers and trailers on the ISL type packets. So we'll pause here and we'll talk about the various types of trunk packets and the most common trunking error in the next video.
Tutorial Information
| Course: | Implementing Cisco IP Switched Networks (642-813 SWITCH) |
| Author: | Greg Dickinson |
| SKU: | 34304 |
| ISBN: | 978-1-61866-041-1 |
| Release Date: | 2012-04-20 |
| Duration: | 8.5 hrs / 102 lessons |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |
VTC Sign up & Benefits
- Unlimited Access
- 81,350 Video Tutorials (14,200 free)
- Video Available as Flash or QuickTime
- Over 715 Courses
- $30 for One Month Access
- Multi-User Discounts Available
