EIGRP Stub – It is actually one of the EIGRP Scalability features but also it helps many other things in EIGRP. Also, in this post, we will share a topology that will be used to explain some design caveats with EIGRP design.

Before we explain the EIGRP Stub, let me explain some EIGRP convergence behaviors.

If you are looking for much more detail on EIGRP Design and Practical Labs, have a look at our EIGRP Training.

When the EIGRP node loses the Connection to the prefixes. If there is no feasible successor installed in the EIGRP topology database.

The router is marked as active and the EIGRP query is sent to every neighbor.

In the above topology, Router D doesn’t know the 192.168.0.0/24 network. Router C sends a summary 192.168.0.0/16. That’s why it replies without asking Router E.

Router B has an alternate path, thus, Router B replies immediately.

Router J doesn’t have any EIGRP neighbors. It replies to the Query immediately.

Router G doesn’t know the 192.168.0.0/24 network. Router F filters the 192.168.0.0/24.

That’s why Router G replies without asking Router H.

So, as you can see, Continue reading

ABR vs ASBR in OSPF. If you are new to Network Engineering and you are learning Dynamic Routing Protocol from scratch, you want to understand the differences between ABR vs ASBR and if there are similarities you would like to learn those too. In this post, we will learn both similarities and differences.

Let’s first understand both of these terms. ABR is purely an OSPF terminology, but ASBR is not. In fact, the detailed post about ASBR and the usage of ASBR in Different Places of Networking is explained in our What is ASBR Blog post.

ABR – Area Border Router is a device which is connecting two different OSPF Areas. One of those OSPF areas has to be Area 0, which is also known as Backbone Area.

In the above topology, R3 is an ABR, connecting Area 0 and Area 1, R4 is an ABR as well, connecting Area 0 and Area 2.

R1 is referred to as Internal Backbone Roter as it doesn’t have any other connection than Area 0, Backbone Area.

In this topology, there is also an ASBR – Autonomous System Boundary Router. It is called ASBR because on that router external prefixes are injected Continue reading

What is MPLS used for?. A very common question among IT Engineers. What are the common use cases of MPLS – Multi-Protocol Label Switching? 

When it is first invented, 20+ years ago, it was considered one of the most scalable ways of doing VPNs. Faster packet processing could be achieved compared to IP destination-based routing because the IP address was 32 bits long but the Labels are just 20 bits long.

But, quickly after the first invention purpose, MPLS VPNs became the most dominant reason for Networks to deploy MPLS – Multiprotocol Label Switching technology.

It supported Ethernet over MPLS – EoMPLS, which is known as Point to Point Layer 2 MPLS VPN, and then soon after VPLS, which is Virtual Private Lan Service, vendors started to support.

VPLS is any to any, or also known as many to many technologies. It means you can connect. your multiple sites in Layer 2 and extend IP subnet by using VPLS technology. It works based on a full mesh of Pseudowires.

After Pseuodowire based Layer 2 VPNs, MPLS actual boom happened with MPLS Layer 3 VPNs.

With MPLS Layer 3 VPN, which is also known as Peer-to-Peer VPN, MPLS CE, Continue reading

Before Starting Cyber Security

Cyber Security, sometimes you might find it as Cyber Operations, CyberOps, is the branch of Network Security that focuses on attacks, from the internet or from the inside of the network, gaps, bugs, look for them before they get used, fix them, and look again.

so the engineers continue to keep looking and fixing, as the internet is always evolving and generating more threats.

How to Study Cyber Security

generally, the domain of security (Information Security, Cyber Security) has nowadays hundreds of certifications and exams from many different vendors.

some are involved in the industry of making security devices/components, others are there just to teach us and make us the best engineers in the domain.

and mostly, cyber stuff comes from companies that focuses on creating the content/references more.

rather than information security exams and books that comes from vendors that produces platforms (Firewalls, IPS, IDS, NGFW, NGIPS, ESA, WSA, and many others).

so as a beginner, up to higher than an expert, many exams should be studied.

of course alongside with some other general/networking exams that you might already hold before studying the cyber security, and these exams will be mentioned below.

Top 10 Cyber Continue reading

CCNP ENCOR vs ENARSI

is it even related?, or should I ask “comparable?”

yes it is both actually, and in this blog we will review both of the exams, talk about the agenda, which one should be taken before the other, and result of both of them.

Relation between CCNP ENCOR vs ENARSI

both the exam belongs to the certificate of Cisco CCNP Enterprise,  and taking each individually will grant you A Certificate!

• Cisco Certified Specialist – Enterprise Core
• Cisco Certified Specialist – Enterprise Advanced Routing and Service

so it is a win-win scenario, but still the question is which one should i take first, and that will be followed below

Difference between CCNP ENCOR vs ENARSI Agenda

ENCOR first, generally a Technology Core exam, focusing on 7 domains of knowledge:

• Architecture
• Virtualization (Device, Path, and Network Virtualization)
• Infrastructure (Switching, Routing, and IP Service)
• Assurance
• Security
• WLAN
• Automation

and NO DEEP DIVE in any of these!!!

while for ENARSI:

• Virtualization (Path Virtualization)
• Infrastructure (Routing and IP Services)
• Security

and that’s it!,

• no Architecture
• in Virtualization no Device nor Network Virtualization, and for the path Virtualization it is different than ENCOR.
• as in the ENCOR you Continue reading

What is ASBR? Autonomous System Boundary Router. This seems easy, it is just used in OSPF, isn’t it?. In fact, that is wrong. You will learn in this post something, that is hopefully you will learn the first time. Let’s have a look at it.

ASBR is a node, that is connecting two or more networks. It can be a router or switch and it can be positioned at the Internet Edge. The router at the Internet Edge is referred to as IGW (Internet Gateway) Router and it can be an IGW Router.

It can be located between two different networks to provide MPLS service for example. Between two networks, service is referred to as Inter-AS MPLS VPNs and in RFC 2547, Section 10, 3 different Inter-AS MPLS VPN Options are explained. In all of them, the routers that are connecting two different Autonomous System is referred to as ASBR as well.

On those routers, usually, BGP runs in Inter-AS MPLS VPN service. OSPF is not mandatory.

Thus, saying it is used in OSPF would be a false claim. It can be used for many different services in the networks and ASBR can run any routing protocol, not just Continue reading

What Layer is MPLS?. This basic question needs to be clarified for the Network Engineers.

MPLS – Multi-Protocol Label Switching first was invented for fast packet processing. As MPLS Label is 20 bits, and IP address is 32 bits, processing MPLS Label was considered faster back in old times.

Today, as of 2022 MPLS is used for many different purposes, one of the most common reasons to have MPLS in the Networks is VPN.

MPLS VPNs, MPLS Layer 2 VPN, and MPLS Layer 3 VPN are two of the most common VPN mechanisms in large Enterprise and Service Provider Networks.

The label is used for two reasons in MPLS VPNs.

A tunnel label or transport label is used for the reachability between the edge devices, PE devices in MPLS networks.

And another label, which is the VPN label is used to differentiate the customers in MPLS VPN.

Both of these labels are placed between MAC Header and IP Header in IP Packets.

Thus, as you can see from the below picture as well, MPLS is commonly referred to as Layer 2.5.

Figure – MPLS is Layer 2.5

As you can see, from the above Continue reading