Routing – routingloop.net

MPLS L3 VPN Forwarding

I never grasped what’s so great about MPLS VPNs until I learned that core routers do not need to carry customer routes. This magic trick greatly reduces state in the MPLS network core. This article will follow a packet’s journey though an MPLS Layer 3 VPN. We will follow an ICMP echo request from CUST2_CE1’s

RT Constraint: A Scalability Technique for MPLS L3 VPNs

28JuneStevenHome Lab, MPLS, Routing

MPLS Layer 3 VPNs (L3 VPNs) are a highly scalable way to deliver private multitenant connectivity. This article will not focus on overall L3VPN operation but will focus on Route Target Constraint, a control plane scaling feature. I’ll be using the topology below for demonstration. Ther is a lot going on here, so I circled

What a Typo Taught Me About B2B Label Switching

24MayStevenHome Lab, MPLS, RoutingMPLS

I’m starting to dive into MPLS based technologies, an area where I have very little experience. I started out with a two “customer site” VPLS network. After getting that working, I added 3rd CE and PE pairing. I made a configuration mistake on PE3 that helped me understand VPLS and MPLS a little better. This

OSPF NSSA and Type-7 LSA Translation

26AprilStevenHome Lab, Routing

OSPF stub areas are a special area where LSA type 5s for external routes are filtered, meaning we will never see a type 5 LSA in a stub area. This is a mechanism to shrink the Link State Database (LSDB) if the area does not need the external routes. The NSSA (That’s Not So Stubby

Integrated IS-IS Metrics

12AprilStevenIPv6, Routing

Intermediate System to Intermediate System, known as IS-IS is a link-state interior gateway routing protocol that was originally designed to route ISO Connectionless Network Protocol (CLNP). IS-IS was standardized in ISO 8473. IS-IS was later extended to route IP. The original IS-IS IP specification was ratified in IETF RFC1195. IS-IS for IP networks is sometimes

BGP Graceful Shutdown

14MarchStevenHome Lab, Routing

BGP Graceful Shutdown is a feature and technique that we can use to minimize traffic loss when administratively disabling a BGP peering session. Graceful shutdown utilizes a well-known community value that was standardized in RFC 8326. We can use the graceful shutdown feature to lower the local preference within the local autonomous system and signal

Remote Triggered Black Hole

1MarchStevenHome Lab, Routing

Remote Triggered Black Hole (RTBH) is a tool we can use to drop unwanted traffic in BGP networks using the forwarding plane. It’s called a remote trigger because once we have the base configuration on all our routers, we can initiate the black hole by making changes on just the “trigger” router. In this article,

Link State Microloops

9NovemberStevenHome Lab, Microloops, Routing

Routingloop.net finally lives up to its name! In this article, I touch on how microloops happen and display how I was able to create and observe a live microloop. What is a microloop anyways? A microloop is a temporary forwarding loop that can occur during network convergence, typically with link state protocols. Why link state?

IS-IS LSP Authentication

29SeptemberStevenHome Lab, Routing

I learned something today that now seems obvious. IS-IS LSP Authentication only impacts the trust of the Link State Packet itself, not IS-IS neighbor maintenance. Neighbor adjacency authentication is a separate function in IS-IS. Neighbors will still form if LSP authentication is mismatched but the LSP content will not be published to the Link State

OSPF v2 LSDB Illustrated

27SeptemberStevenHome Lab, Routing

In this lab exercise, I am going to attempt to draw a diagram of the network based on the OSPF Link State Database (LSDB) using the virtualized network shown below. The diagram will be based on R1’s view of the network. R1’s OSPF Router ID (RID) is 1.1.1.1. Let’s start by examining R1s LSDB at

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Category Archives: Routing