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.
OSPF LSA
1. LSA Types OSPF uses different LSA types (Link State Advertisements) to share routing information between routers and build its LSDB (Link State Database). Each LSA type has a specific purpose and flooding scope where it is flooded only within or between areas. Find next more details about the LSA Types: 2. Wireshark First, let’s see the encapsulation of […]
OSPF Cheat Sheet
OSPF – Interior Gateway Protocol (IGP) Type: Link State Algorithm: Dijkstra Metric: Interface cost is auto-derived from bandwidth unless manually configured. Cost = reference-bandwidth / bandwidth Default reference-bandwidth = 100 000 000 (100 Mbps) External Metrics: Type 1: The sum of the internal costs plus the external cost. Type 2: Only the external cost assigned […]
OSPF Virtual Link
1. Intro For backbone areas only, create a virtual link to use in place of an actual physical link. All area border routers and other routing devices on the backbone must be contiguous. If this is not possible and there is a break in OSPF connectivity, use virtual links to create connectivity to the OSPF […]
OSPF Overload
1. Intro OSPF Overload: configure the local routing device so that it appears to be overloaded. You might do this when you want the routing device to participate in OSPF routing, but do not want it to be used for transit traffic. There is no overload bit, like we have in ISIS Overload. Instead, OSPF […]
OSPF Summarization
1. Intro In the previous post we applied OSPF basic config on our test network. We had 2 areas; one of them is a Totally NSSA area. In this post will do some OSPF route summarization on the same topology, continuing from where we left off. For easy reference find the OSPF database as it […]
OSPF Basic config
1. Intro In this post we will apply OSPF basic config on our test network. We have 2 areas; one of them will be a Totally NSSA area. In the next post will do some OSPF route summarization on the same topology. 2. OSPF Basic config We will configure a topology with multiple areas: The […]
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 […]