In the previous blog post, we looked at a few fundamental OSPF concepts, including neighbor and adjacency formation. As we continue through the basics of OSPF, this post will examine router roles, timers, and metric calculation.
A designated router (DR) is the router interface that wins an election among all routers on a multiaccess network segment such as Ethernet. A backup designated router (BDR) is the router that becomes the designated router if the current designated router has a failure on the network. The BDR is the OSPF router with the second highest priority at the time of the last election. OSPF uses the DR and BDR concept to assist with efficiencies in the operations of OSPF.
Keep in mind that a given OSPF speaker in your network can have some interfaces that are designated and others that are backup designated, and others that are non-designated. If no router is a DR or a BDR on a given...
The OpenShortest Path First (OSPF) dynamic routing protocol is one of the most beloved inventions in all of networking, widely adopted as the Interior Gateway Protocol (IGP) of choice for many networks. In this blog series, you'll be introduced first to the basic concepts of OSPF and learn about its various message types and neighbor formation.
Where does the interesting name come from when it comes to OSPF? It is from the fact that it uses Dijkstra's algorithm, also known as the shortest path first (SPF) algorithm. OSPF was developed so that the shortest path through a network was calculated based on the cost of the route. This cost value is derived from bandwidth values in the path. Therefore, OSPF undertakes route cost calculation on the basis of link-cost parameters, which you can control by manipulating the cost calculation formula.
As a link state routing protocol, OSPF maintains a link state database. This is a form of a network...
One of the big announcements this week at Cisco Live was the launch of their new DevNet certification track. Cisco CEO Chuck Robbins reiterated the fact that knowledgeable engineers are always going to be in-demand. Contrary to what many believe, network automation and A.I. integration is not designed as a replacement for those skills, but rather these advancements allow the ability to manage numerous network devices and their services through software. For large scale networks, usage of API’s for automation is the way of the future.
The launch of this new certification track is aimed at joining the skills of software developers with network professionals, with the goal of accelerating the progress of network automation in organizations throughout the world.
Here's a breakdown of the current DevNet certification offerings:
This entry-level certification is accessible to those who are...
By now I'm sure you've heard of the sweeping changes Cisco is making to their certification tracks, which was announced at Cisco Live on Monday June 10, 2019. I covered the CCNA exam changes in a previous post, so here I'll specifically address updates to the CCNP track.
First, if you've already started working toward any current CCNP certification - keep going! You have until February 24, 2020 to complete your certification, and in the new program, you'll receive credit for work you've already completed.
Let's begin by looking at the current list of CCNP certifications, set to expire next February:
Now, here are the new CCNP certifications that will be rolling out:
You may notice the absence of CCNP...
On Monday June 10, 2019 Cisco announced an unprecedented revamp of their certification program. This post dives into one of the major updates, the new CCNA certification. (We'll have a future blog post with updates on the CCNP changes.)
First, if you’re currently preparing for your CCNA R/S (or any other CCNA for that matter), don’t panic. You have until February 24, 2020 to complete your certification, at which time you’ll be given the new CCNA certification, plus a “badge” indicating your area of specialization (based on which CCNA you earned). So, Cisco recommends you “keep going” if you’re working towards any CCNA certification.
Even if you’re just thinking about going after a CCNA cert, personally, I would do it now before the February deadline hits.
However, just having a current CCENT certification won't help. You'll need a full CCNA to be granted the new CCNA certification. So, if you do just have your CCENT,...
Cisco just announced their certification program is getting a MAJOR update. Here’s what you need to know:
This post is the 6th and final in a series of Border Gateway Protocol (BGP) posts. If you missed any of the first five parts, here are the links:
In this post, we're going to take a look at how we can work with BGP in IPv6.
You will recall from this chapter that BGP was constructed to support many different protocols and NLRI right out from its creation. As a result, we have robust support for such technologies as IPV6, MPLS VPNs, and more.
You will also relish in the fact that once you master the basics of BGP that we have covered in this , working with BGP in IPv6 is much more similar than it is different!
BGP is so remarkably flexible, as discussed earlier in this chapter, you can use IPv4 as the “carrier” protocol for IPv6...
This post is the 5th in a series of Border Gateway Protocol (BGP) posts. If you missed any of the first four, here are the links:
In this post, we're going to take a look at BGP scalability mechanisms and related concepts.
Just as IP address depletion has been a concern with the Internet, so has the depletion of available autonomous system numbers. To help solve this, the engineers turned to a familiar solution. They marked an AS number range as private-use only. This permits you to experiment with AS construction and policy in a lab (for example) and use AS numbers that are guaranteed not to conflict with Internet-based systems.
Remember, the AS number is a 16-bit number permitting up to 65,536 AS numbers. The private space is marked as 64512-65535.
This post is the 4th in a series of Border Gateway Protocol (BGP) posts. If you missed any of the first three, here are the links:
In this post, we're going to take a look at configuring BGP to advertise Network Layer Reachability Information (NLRI), and also the configuration of a BGP routing policy.
Before we even begin advertising NLRI using our various commands in this section, let’s take a moment to discuss an old feature of BGP that Cisco disables by default for you. The feature is called BGP synchronization. For proof that Cisco has disabled this feature on your device, just perform a show running-configuration on one of your lab BGP speakers and under the BGP process you will find the command no synchronization. If enabled, the synchronization feature prevents a BGP speaker from entering prefixes into BGP...
This post is the 3rd in a series of Border Gateway Protocol (BGP) posts. If you missed either of the first two, here are the links:
Now, in this post, you'll learn about how BGP neighborships are formed, within an autonomous system, between autonomous systems, and even between routers that are not directly connected. Also, we'll check out BGP authentication.
Given that BGP is an AS-to-AS routing protocol, it would make good sense that external BGP (i.e. eBGP) is a key ingredient in its operations. The very first thing that we need to keep in mind with eBGP is that the standards are built so that there is a requirement for a direct connection. This is something that we can work around (of course), but this point is worth consideration. Because a direct connection is assumed, the BGP protocol does two things: