CML-Free Layer 3

Over the years, I’ve created a bundle of about 75 lab exercises here at the blog, called Config Labs. The idea is to read the web page for the lab, then do the lab, and then check your [...]

OSPF chooses the best route to reach a subnet based on the lowest cost among all possible routes. OSPF calculates the cost as the sum of the OSPF interface costs of all outgoing interfaces in the [...]

OSPF uses a router’s Router ID (RID) to identify each router. We see the RID in many OSPF verification commands, so using predictable, known OSPF RID values can help people operate [...]

The OSPF network type setting happens to be one of the more useful optional OSPF features. This setting changes a couple of details about how OSPF operates on an interface. Ethernet WAN links [...]

OSPF includes many optional features. Depending on the network, particularly the WAN, you may ignore some of those features while possibly using others. The choice to influence which router [...]

From the first days of OSPF in Cisco routers, OSPF configuration has included a network command. The network command enables OSPF on that router’s interfaces, but it uses indirect logic. In fact, [...]

This blog post begins with a router triangle, IP addresses, and working interfaces. All routers can ping their own IP addresses, but the routers only know their own connected routes. You job: Add [...]

The first time you learn about IP routing, some of the basic ideas just do not click until you think hard about the contents of the IP routing table. One of the best tools to make you think about [...]

One of the best ways to learn IPv4 routing is to think hard about IPv4 static routes. Today’s lab gives you more of that with a typical config lab. It starts with a topology and with IPv4 [...]

More practice practice practice! This time, you get some basic IP addressing requirements. Your job: calculate the IP addresses to be used by routers and hosts, and create the router [...]