gurfin gurf1n

After about a month of rest from studying I am itching to get started on the next certification. Naturally I will be going for one of the specialisation certifications within the CCNP Enterprise track. I have, since about 4 years back, planned to do CCNP, DevNet Associate, ENCOR and then ENARSI. So this will then be the beginning of the end of the initial certification plan that I had cemented.

It has been a while since I last posted to this blog. As is apparent, if one studies the topics I have been covering for the past months, I have been studying for the Cisco CCNP ENCOR 350-401 certification. On the 23rd of April 2025, I passed on my first attempt. That being said, I was sure that I would fail the exam and was mentally not prepared for a passing grade.

Who does not like a good old tunnel? There are different tunnel types available for us to use when building our networks. The ones we will cover here are GRE and IPsec, as well as briefly mentioning DMVPN, GET VPN and FlexVPN. GRE Generic Routing Encapsulation (GRE) is one of the most versatile tools to keep in your networking tool belt. This type of tunnel provides encapsulation without any sort of encryption.

In the beginning, God created IPv4 When the internet was first created, large public IPv4 address blocks were handed out and assigned to organizations. When the usage of the internet grew it became quite apparent that the available IPv4 address space would not be enough. One of the most implemented solutions to this problem is Network Address Translation (NAT), which allows Layer 3 capable devices to rewrite source and/or destination addresses.

This post will be covering some useful, but less heavy technologies, namely NTP and FHRP. These are essential to building a resilient and well functioning network. It’s funny, every time I work with NTP I am reminded of when I took a certain exam. During one of the labs there was a need for configuring NTP on a router - simple enough, I though. I spent about 40% of the entire allotted exam time on trying to get NTP to synchronize - turns out, that everything was correctly configured and NTP was just slow… 🤦‍♂️

Quality of Service (QoS) is a technology that you hope you never need to use, but when you do, it’s really handy! The core principal of QoS is to allow us to affect the network resource allocation based on the given service and it’s requirements. QoS is a technology that only becomes relevant when you have a network that is strained in one or more of the following ways: Insufficient bandwidth Jitter or latency Packet loss In situations where you are not experiencing the aforementioned issues, QoS will not bring any benefit to your network.

Ever wanted to try being your own ISP? Ever wanted to setup a transit AS while hosting some services on IP-addresses you own? Enter “dn42” (https://dn42.eu/), where you are able to build an overlay network of software or hardware based routers and do BGP peering with hundreds of other AS:s. For a couple of months now I have been itching to setup a dn42 network to learn some more about software based routing and networking in the cloud.

I have a special appreciation for the multicast technology. Back when I used to work in first line support for a Swedish service provider of IPTV, I was always intrigued by the efficiency of using multicast to deliver the TV to peoples homes. Using multicast drastically reduced the bandwidth requirements for the central streaming sources that were used to send out the TV broadcasts onto the fiber networks. Now, in recent years service providers have moved away from this and into using unicast streaming in stead.

A project I have recently undertaken requires me to use linux based routing processes to communicate with other peers. The software I have chosen to run is bird2, which allows me to establish adjacencies with and BGP peer, Cisco or other. I have noticed however, that I find myself google:ing the same commands over and over again. So I though I would collect all the commands I have found to be useful in a blog post, that I myself can refer back to.

Summer and winter time adjustments is something that causes quite the headache when you want all your devices to have an accurate clock. This is especially important when you are going to review logs. I will therefore share a short snippet of config which can be used to set the clock of a Cisco IOS-XE device to correctly adapt to the summer/winter time. clock timezone SWEDEN 1 0 clock summer-time SUMMERTIME recurring last Sun Mar 3:00 last Sun Oct 3:00 yeet