RIP is probably one of the oldest routing protocols and if i'm honest, it should stand for Rest In Peace instead of Routing Information Protocol. In saying that, at one stage it was a great little lightweight protocol. RIP is a distance vector routing protocol that uses hop count as a metric. Each router in the path to a network is considered a hop.
EIGRP is considered a hybrid distance vector protocol. While EIGRP does keep track of hop count as a metric, it doesn't so much use it as a metric like RIP does. Instead EIGRP uses path attributes to determine the best route. Don't worry too much about these path attributes as I will go through them later.
Let's start with how EIGRP sends routing information. EIGRP uses the multicast address 224.0.0.9 to send its messages using the EIGRP protocol number 88. There are 5 types of EIGRP messages that a router will send.
This article brings us to the Layer 3 part of the Network world and routing in general. In order for a packet to be sent from its source to its destination, our network devices, either a Router or a MLS, need to know how to get there. And to do that, Routers need to know which next-hop device the packet should be forwarded to and in which direction (Interface) that next-hop device is. There are several ways for routers to learn this information.
In my last few articles, I've talked about etherchannels and what they are and how they work as far as being a layer 2 etherchannels goes. But what if we want to load balance across layer 3 interfaces and route traffic? Well, Cisco routers and switches (MLS switches at least) support both Layer 2 and Layer 3 etherchannels.
PAgP or Port Aggregation Protocol, is a Cisco proprietary link aggregation protocol. This protocol works in a similar way to LACP in that it uses PAgP messages to negotiate and establish the etherchannel bundle. Like LACP, PAgP has two modes for configuration:
In my previous article, I talked about the basic concept of etherchannels and how they work to provide additional redundancy and bandwidth in our networks. I also talked about how to configure an always on etherchanel. In this article, I will talk about how to dynamically establish an etherchannel using LACP (Link Aggregation Control Protocol)
We know that in a fully redundant Layer 2 topology, STP will find a Root Bridge, Find the shortest path to the Root Bridge, and block all other ports as shown in the below diagram.
In my previous articles about VTP I mentioned that frames are sent over all trunk ports and when utilising VLANs on switches to segment a network you need to use trunk ports to transport frames from each VLAN between network devices. But how do you configure a trunk port?
The main functions of VTP V3 are exactly the same as with VTPv1 and V2, however VTPv3 has some additional features and configuration requirements.
VTP or Virtual Trunking Protocol, is a Cisco proprietary protocol that is used to share VLAN information between switches. In a small topology such as our little 3 switch topology or it a small office network where you might have 3 or 4 switches, configuring VLANs manually on each switch might not be such a big deal. But think about a large scale campus network or Datacenter network where you have hundreds or thousands of VLANs and having to manually configure those VLANs or make changes on each device. This is why Cisco invented VTP.
