Blog posts


Submitted by rayc on Wed, 11/17/2021 - 08:41

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 Part 1

Submitted by rayc on Tue, 11/16/2021 - 08:09

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 to send its messages using the EIGRP protocol number 88. There are 5 types of EIGRP messages that a router will send.

Routing Protocols

Submitted by rayc on Mon, 11/15/2021 - 14:37

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.

Layer 3 etherchannels

Submitted by rayc on Sat, 11/13/2021 - 06:44

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. 


Submitted by rayc on Mon, 10/25/2021 - 10:51

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:


Submitted by rayc on Mon, 10/25/2021 - 10:51

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)

VTP v3

Submitted by rayc on Mon, 10/25/2021 - 09:52

The main functions of VTP V3 are exactly the same as with VTPv1 and V2, however VTPv3 has some additional features and configuration requirements. 

  • VTPv3 is backward compatible with switches running V1 and V2. 
  • Allows on the VTP Primary Server to make VLAN changes.
  • Supports all 4094 VLANs. 
  • Supports propagating MST configuration changes
  • Provides feature specific primary server configuration.
  • Allows the use of PVLANs (Private VLANs)
  • Per Port VTP configuration is supported


VTP v1 and v2

Submitted by rayc on Mon, 10/25/2021 - 09:52

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.