Home Lab – routingloop.net

EIGRP in Clos Topologies

Link state protocols or BGP are typically used for underlay routing in data center fabrics, deployment of these protocols is Clos (aka spine and leaf) topologies are well documented. I decided to experiment with EIGRP to get a better understanding of its operation in such topologies. Although I don’t expect to ever see a production

A Thing About EIGRP Summaries

2OctoberStevenHome Lab, Routing

IP route summarization, sometimes called aggregation, allows us to suppress the advertisement of multiple longer prefixes into a shorter prefix that encompasses a range of more specific routes. There are plenty of excellent guides on summarization, so I’ll spare those details here and jump straight into some EIGRP specific things about summaries. Demo Network For

Clear arp-cache vs clear ip arp

20SeptemberStevenHome Lab, Routing

Cisco IOS CLI provides two different commands that seem the same on the surface but have a slightly different outcome on the wire. Based on the title you probably guessed that it’s clear arp-cache vs clear ip arp. To see the difference, I connected two routers on network 10.0.0.0/30 with a SPAN enabled switch in

TCP CUBIC vs BBR Pt. 1

1AugustStevenHome Lab

TCP congestion control algorithms have a tough problem to solve. They need to estimate the available capacity of a network path without any knowledge of network. Remember that TCP runs in the end hosts. It’s important to estimate the network capacity to achieve the maximum throughput for a single flow while sharing network resources with

Don’t Have a Bad Day

31MarchStevenHome Lab, Routing

Anycast RP with Multicast Source Discovery Protocol (MSDP) is a great way to provide fault tolerance to your multicast network. Configure another router with the RP address, bang out a few msdp commands on the RP routers and you’re all set for a basic anycast RP design. It’s important to not get tunnel vision and

EIGRP Metric Calculation

27MarchStevenHome Lab, Routing

If you’ve worked with or studied EIGRP, you’ve probably seen that scary formula with the K values that EIGRP uses to calculate routing metrics. It turns out that if you’re using the default K values so that only bandwidth and delay are being considered, the math involved isn’t that bad. In this article we’ll explore

IPv6 Next Hop

16MarchStevenHome Lab, IPv6, Routing

Over the last two weeks I’ve been focusing on strengthening my knowledge of IPv6 and it got me thinking about usage of link local addresses as the next hop for routing. It became apparent that this difference from IPv4 makes it possible to have equal cost next hops via the same output interface and for

IPv4 Fragmentation

2MarchStevenHome Lab, Routing

One of the attributes that helped IPv4 stand the test of time is the ability to slice and dice big datagrams into multiple smaller ones on the fly. This provides tremendous flexibility for different data links and their maximum packet size, reduced MTUs inside of tunnels, and the like. The process of chopping up IP

Joining MST and PVST Domains

16FebruaryStevenHome Lab, Switching

Multiple Spanning Tree Protocol (MST) allows network operators to map one or more VLANs to a Spanning Tree Protocol instance. For example, VLANs 1,2,3,4, and 5 can be mapped to STP instance 1 while VLANs 6,7,8,9 and 10 are mapped to STP instance 2. Consolidating multiple VLANs into a single STP instance requires less overhead

Spanning Tree BackboneFast

8FebruaryStevenHome Lab, Switching

To close out this 3-part series on Spanning Tree convergence optimizations we’ll be diving into Spanning Tree BackboneFast. This feature allows “classic” STP 802.1D bridges to converge faster when a remote bridge loses connectivity to the root bridge, i.e. this allows faster convergence to indirect link failure. Demo Network To demonstrate convergence with and without

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