Category Archives: Cisco

OSPFv2 vs OSPFv3 LSA’s

In this post we will talk bout the differences between OSPFv2 and OSPFv3 LSA’s An LSA (Link state advertisement) is a packet-type used by OSPF to communicate information about to network to its neighbors. OSPFv2 uses a number of different LSA’s as listed below. LSA Type 1 – Router LSA – Generated by all routers… Read More »

OSPF Interface Costs

In this example we will use OSPF Costs to allow us to load balance between links. We have 2 paths to router 2. The fist is directly connected the second is via R1. Lets first trace to R2 and see what path we are using R3#traceroute Type escape sequence to abort. Tracing the route… Read More »

Reliable Default Route – OSPF

In this post we will configure and test a reliable default route using OSPF. First we need to look at the network digram. R1, R2 and R3 are all in the same OSPF area. R3 and R4 are peering via BGP. All devices have a loopback interface x.0.0.0/8 where X is the routers number. As… Read More »

Cisco Basic Zone Based Firewall

In this post we will cover the basic set up of Zone Based firewalls on the Cisco routing platform. We will use the following network for our example. Router R2 will be our Zone Based firewall (ZBF) and R3 will be the outside of our network and C1 is our client computer (which is another… Read More »

BGP Communities

In this post we are going to use the BGP community PA to set the Local preference for our routes. We will be using the following diagram The Local Preference is a BGP Path Attribute (PA) which is a well-known discretionary PA. The route with the highest Local Preference is preferred over the route with… Read More »


In this post we will cover MPLS VPN using the following digram. We have a customer with 2 different sites. We need to creat an MPLS VPN so that site A and site B can share routes. We will be using EIGRP between the 2 sites and between the CE and PE. We will be… Read More »

BGP Route Reflector

In this post I will explane BGP route reflectors. We will be using the following network digram for this post. Just like all routing protocols BGP has its own loop prevention mechanism. One of these mechanisms is the split horizon rule. The Split horizon rule for routing protocols is “don’t send updates back on the… Read More »

Site To Site VPN

In this post I will explain how to set up a site to site VPN on Cisco routers. First of all we need our network setup like this. Once we have set up the network we need to assign IP address according to the dirgram.  The next part will be to set up the VPN.… Read More »

OSPF Virtual Link

In OSPF everything has to connect to the backbone area with is area 0. So if we had a situation where we had 3 areas, area 0, area 1 and area 2 and area 2 was connected to area 1 and not directly connected to area 0 then we would have a problem. This is… Read More »

Basic BGP setup on Cisco

To begin with we need to set up the below network. We need to configure the IP addressing for all routers. Now we have setup the network we need to configure the iBGP neighbour relationship between R1 and R2. iBGP (internal BGP) is a type of BGP that is used between routers in the same… Read More »