Routing – routingloop.net

Don’t Have a Bad Day

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

Exploring CEF

25FebruaryStevenRouting

There are a few fundamental actions that a router must perform to take a packet coming in one interface and forward it out of another. The router must perform lookups to determine the exit interface and next hop information, it must rewrite the data link layer header and trailer for the egress link, and if

PIM RP Redundancy that (kinda) Works

10JanuarySteven1 CommentHome Lab, Routing

I spent a few minutes thinking about anycast RP for PIM sparse-mode deployment and thought of a way to provide RP redundancy without auto-RP or BSR to dynamically learn RPs, and without using MSDP to synchronize active source information between anycast RPs. There is a major pitfall to this approach but it can work. Demo

AS Boundary Links in IGP?

14DecemberStevenENSLD, Home Lab, Routing

Lately I’ve been focusing on honing my BGP skills to prepare for the ENSLD exam. While this isn’t a configuration focused exam, I’ve been spending some lab time on it to reinforce design concepts. I built out a 29-node lab in Cisco modeling labs featuring eBGP, iBGP, route reflectors, BGP confederations, and eBGP third party

Information Hiding in Routing Systems

19NovemberStevenHome Lab, Routing

One of the most effective methods to build stable and scalable routing designs is to summarize topology and reachability information in routing protocols. Summarization can help networks converge faster and limit the number of routers that need to perform route calculations when an event such as a link flap occurs. However, there are tradeoffs to

Static Routes, Exit Interfaces, Ethernets

9SeptemberStevenHome Lab, Routing

Ethernet Ethernet allows multiple hosts to share the same network segment. There are only 3 ways to deliver a frame to another computer over ethernet. You can send a broadcast and interrupt every host on the segment, send a multicast and hope that the intended receiver is listening, or send a unicast by placing the

Faster EIGRP Feasible Successor Failover

10AugustStevenHome Lab, Routing

The feasible successor is EIGRP predetermining an alternate next hop to reach a destination for fast failover. The feasible successor route is stored in the EIGRP topology table but is not installed in the RIB/FIB by default. The variance command can be used to promote the feasible successor to the routing table and traffic will

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Category Archives: Routing