Routing
Routing is the process of selecting the best path for data packets to travel across one or more networks from a source to a destination. Over time this category will include posts for static routing, routing protocols, preference/administrative distance, redistribution and many more.
Different routing subcategories to explore:
Stay tuned for more.
ISIS Cheat Sheet
ISIS – Interior Gateway Protocol (IGP) Type: Link State Algorithm: Dijkstra Metric: 10 for any interface0 for Loopback interface Metric Type: Narrow and Wide by default. But, ISIS silently limits metric to 63.In modern ISIS deployments we should enable wide-metric-only. Preference (AD): 15 / 18 (L1/L2 Internal)160 / 165 (L1/L2 External) PDU Types IIH IS-IS […]
ISIS metric – 3rd trap, the differences between IPv4 and IPv6
1. Intro In this part we will focus on the ISIS IPv6 metric, more specifically, the differences between IPv4 and IPv6. But before that, let’s remind ourselves that this post is part of a 3 part series about the impact of ISIS Narrow and Wide metrics: 2. The test topology The topology is the same, […]
ISIS Metric – 2nd trap, the unexpected impact of wide-metrics-only
1. Intro In this part we will focus on the use unexpected impact of the wide-metrics-only knob. But before that, let’s remind ourselves that this post is part of a 3 part series about the impact of ISIS Narrow and Wide metrics: 2. The test topology We will update our test topology to demonstrate the […]
ISIS Metric – 1st trap of Narrow and Wide metrics
1. Intro The ISIS Metric topic will have 3 parts: 2. The ISIS metric defaults A quick review of the ISIS metric defaults: 3. The unexpected impact of using both Narrow and Wide by default As already mentioned, Junos uses a combination of both Narrow and Wide metrics. But why use both? Well, the advantage […]
BGP Attributes
BGP attributes are grouped in four main classes: These attributes are very important to master for the JNCIE-SP lab exam.
RIP – Quick notes
RIP is a distance-vector Interior Gateway Protocol. It calculates the shortest path by evaluating the distance to reach the prefix (vector). The distance used by RIP is the hop count. Routing updates are sent at a regular basis, which is 30 seconds by default. There are two versions of the RIP protocol, where version 2 […]
OSPF Neighborship Requirements and Troubleshooting
1. Intro It is often times a struggle to bring up an OSPF Neighborship between two routers. Well, it can be if you don’t clearly know all requirements. In this post we will see all OSPF neighborship requirements and how to troubleshoot when the neighbors are not UP. As a network engineer we must know […]
ISIS Overload timeout – Testing the timeout knob
1. Intro First of all, lets quickly review the what the official documentation is saying about the ISIS overload timeout knob: You configure or disable overload mode in IS-IS with or without a timeout. Without a timeout, overload mode is set until it is explicitly deleted from the configuration. With a timeout, overload mode is […]
ISIS Overload – Learn with a practical example
1. Intro The Overload statement causes the routing device to continue participating in IS-IS routing, but prevents it from being used for transit traffic. It is useful sometimes to deviate the traffic away from a particular router, so we can avoid traffic being impacted. We typically have 2 scenarios: Bonus scenario: ISIS will make this […]
ISIS PDU – Types and Wireshark sample packets
Intermediate systems send and receive packets and relay (forward) packets. ISO packets are called ISIS Protocol Data Unit packets, or in short ISIS PDU. There are four PDU types and all share a common header. This common header has the same structure and information for all four PDU types, except the ‘PDU Type’ filed as […]