Blog – Page 3 – routingloop.net

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

ToS Byte Reference Sheet

10JanuaryStevenENSLD

This morning I put together a spreadsheet all about the Type of Service byte and it’s associated DSCP and ECN markings. Feel free to download it and reference or modify it as you see fit.

STP Priority

31DecemberStevenHome Lab, Switching

When learning protocols, I like to build out a lab, take packet captures, debugs, and show commands and try to understand and justify the output. My most recent exercise is with PVST+. I built out the 6-switch topology below in CML. One of the first things I experimented with is bridge priority configuration. VLAN 10

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

OSPF in Phase 1 DMVPN Networks

21JuneStevenENSLD, Home Lab, Routing

When designing hub and spoke networks, most architects will opt for distance or path vector routing protocols when given the choice. I don’t blame them, distance/path vector provides several benefits that work well in hub and spoke topologies. EIGRP based hub and spoke networks can scale to thousands of spokes without much work. Route summarization

OSPFv2 Link State Advertisements

14MayStevenHome Lab, Routing

Link State Advertisements (LSAs) are one of hardest things to understand while learning OSPF. I believe that having a basic understanding of the LSA types and being able to interpret them is crucial to understanding OSPF operation. LSAs are flooded to populate the Link State Database (LSDB) on routers participating in OSPF. The content of

Back to the Books

26AprilSteven1 CommentENSLD

Back in mid-February, I sat and passed Cisco’s 350-401 Enterprise Core exam. The final crunch before the exam wore me thin so I took a few days of rest and celebration. The current CCNP structure requires passing a core exam and 1 concentration exam within the same track. During my ENCOR studies I was torn