The first post in this BGP mini-series looked at setting up BGP peering between routers. Now we’ll take things a step further and actually exchange some routing information between those peers. Here’s the network: The basic BGP config on each router looks like this: R1#sh run | s router router bgp 1 no synchronization bgp […]
We know that two OSPF routers will become neighbours if they can agree on certain parameters (see my previous post for details) and this is great, but suppose the bad guys were able to connect their own router to the same data link and then cause OSPF routing mayhem – how do we stop this??? […]
In this post we’re going to take a look at the process of two Cisco routers forming an OSPF neighbour adjacency, with an emphasis on what’s going on at a packet level. We’ll look at the packets sent and received on a multi-access network type, in this case Ethernet. Here’s our network: Our OSPF config […]
There are many reasons why you would want to implement route filtering. A good example would be to prevent routes to transit networks being advertised to a branch router, because no host in the branch would ever need to send packets to a host in the transit network. Filtering in EIGRP is configured using the […]
There are a couple of gotcha’s when running EIGRP over a WAN technology such as Frame Relay, as opposed to a LAN technology like Ethernet. To demonstrate one of them let’s consider a typical Frame Relay network operating in a hub and spoke configuration, with our HQ router being the hub and our East and […]
We know that enabling EIGRP on an interface has two effects: EIGRP Hello packets will start being sent out of the interface to multicast address 224.0.0.10. This means that neighbour relationships (adjacencies) can be formed with other routers directly connected to the same subnet and using the same EIGRP AS number the network that the […]
EIGRP will load balance traffic across up to 16 links (4 by default) of equal cost. One nice feature of EIGRP is that it can also be configured to load balance across unequal cost links, as opposed to other routing protocols like RIP and OSPF. Our topology is made up of two routers connected to each […]
So, my CCNP studies slipped onto the back burner recently as I focussed on passing my JNCIA-Junos cert, so it’s time to pick up where my last post left off and move on from a basic EIGRP config to some more advanced stuff. We know that two EIGRP routers will become neighbours if they have the […]
I passed the JNCIA-JUNOS (JN0-101) exam today 🙂 after a couple of weeks study, so thought I’d knock up a quick blog post about the experience and how it compares to other vendor exams I’ve taken. Firstly, the main reason I went after this cert is that I worked on the deployment of a new […]
Hello, is there anybody in there? Just nod if you can hear my EIGRP hello packets being multicast to 224.0.0.10…. Apologies to any Pink Floyd fans out there, but the opening line to Comfortably Numb describes perfectly what happens when an interface starts participating in an EIGRP routing process (well, not really). As […]