Author: ccie14023

TAC Tales #15: Loopy

I’ve mentioned in previous TAC Tales that I started on a TAC team dedicated to enterprise, which made sense given my background.  Shortly after I came to Cisco the enterprise team was broken up and its staff distributed among the routing protocols team and LAN switch team.  The RP team at that time consisted of service provider experts with little understanding of LAN switching issues, but deep understanding of technologies like BGP and MPLS.  This was back before the Ethernet-everywhere era, and SP experts had never really spent a lot of time with LAN switches. This created a big problem with case routing.  Anyone who has worked more than 5 minutes in TAC knows that when you have a routing protocol problem, usually it’s not the protocol itself but some underlying layer 2 issue.  This is particularly the case when adjacencies are resetting.  The call center would see “OSPF adjacencies resetting” and immediately send the case to the protocols team, when in fact the issue was with STP or perhaps a faulty link.  With all enterprise RP issues suddenly coming into the same queue as SP cases, our SP-centric staff were constantly getting into stuff they didn’t understand. One such case came in to us, priority 1, from a service provider that ran “cell sites”, which are concrete bunkers with radio equipment for cellular transmissions.  “Now wait,” you’re saying,...

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On Being a Dinosaur

An old networking friend whom I mentored for his CCIE a long time ago wrote me an email:  I’ve been a CCIE for 10 years now, he said, and I’m feeling like a dinosaur.  Everyone wants people who know AWS and automation and they don’t want old-school CLI guys. It takes me back to a moment in my career that has always stuck with me.  I was in my early twenties at my first job as a full-time network engineer.  I was working at the San Francisco Chronicle, at the time (early 2000’s) a large newspaper with a wide circulation.  The company had a large newsroom, a huge advertising call center, three printing plants, and numerous circulation offices across the bay area.  We had IP, IPX, AppleTalk and SNA on the network, typical of the multi-protocol environments of the time. My colleague Tony and I were up in the MIS area on the second floor of the old Chronicle building on 5th and Mission St. in downtown San Francisco.  The area we were in contained armies of mainframe programmers, looking at the black screens of COBOL code that were the backbone of the newspaper systems in those days.  Most of the programmers were in their fifties, with gray hair and beards.  Tony and I were young, and TCP/IP networking was new to these guys. I was telling Tony how...

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Cisco Live US 2018

Cisco Live Orlando has wrapped up, at least for me, and I can relax until Cisco Live Europe in January.  I never realized how much work goes into Cisco Live until I became a TME.  Building labs, working on slides, preparing demos, and arranging customer meetings is a months-long process and always a scramble at the end.  It’s a great show, and I can say that having attended as a customer.  It’s more fun and less work to be an attendee, but for technical marketing engineers, it’s still a blast and the highlight of the year. Orlando had a...

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Two Years of Ten Years a CCIE

Two years ago I published my Ten Years a CCIE series.  Actually, I had written the series a couple years before I published it, but as I say in my introduction to the series, I felt it was a bit self-indulgent an uninteresting, so I scrapped it for a while.  The original pieces were dictated, and I’ve been meaning to go back and clean up some of the grammatical errors or grating phrases, but haven’t had the time.  Not a lot of people have read it, nor did I expect many to read it, since I generally don’t advertise the blog in social media, or anywhere really.  But the feedback from the few who have read it has been positive, and I’m gratified for that. Things have changed a lot since I got into networking in 1995, and since I passed my CCIE in 2004.  But it’s also amazing how much has stayed the same.  TCP/IP, and in fact IPv4, is still the heart of the network.  Knowledge of OSPF and BGP is still key.  For the most part, new controllers and programmable interfaces represent a different way of managing fundamentally the same thing. The obvious reasons for this are that networks work and are hard to change.  The old protocols have been sufficient for passing data from point A to point B for a long time.  They’re not perfect but they...

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TAC Tales #14: Stuck in Active

Everyone who’s worked in TAC can tell you their nightmare case–the type of case that, when they see it in the queue, makes them want to run away, take an unexpected lunch break, and hope some other engineer grabs it.  The nightmare case is the case you know you’ll get stuck on for hours, on a conference bridge, escalating to other engineers, trying to find a solution to an impossible problem.  For some it’s unexplained packet loss.  For others, it’s multicast.  For me, it was EIGRP Stuck-in-Active (SIA). Some customer support engineers (CSEs) thought SIA cases were easy.  Not me.  A number of times I had a network in total meltdown due to SIA with no clue as to where the problem was.  Often the solution required a significant redesign of the network. As a review, EIGRP is more-or-less a distance-vector routing protocol, which uses an algorithm called DUAL to achieve better performance than a traditional DV protocol like RIP.  I don’t want to get into all the fun CCIE questions on the protocol details, but what matters for this article is how querying works.  When an EIGRP neighbor loses a route, it sets the route as “Active” and then queries its neighbors as to where the route went.  Then, if the neighbors don’t have it, they set it active and query their neighbors.  If those neighbors don’t have...

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