Comment by AStonesThrow | Hacker News Reader

Comment by AStonesThrow | Hacker News Reader

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True indeed, true indeed.

Cisco offers some simulator tooling. It basically virtualizes a lot of networking devices and allows you to play LEGO/SimCity with them: Cisco Packet Tracer

https://www.netacad.com/learning-collections/cisco-packet-tr...

Now, we built toy networks from scratch while I was working toward my certification. Surely larger-scale simulation files could be loaded into Packet Tracer. And perhaps, vendors have simulators on a larger scale than the free downloads?

https://developer.cisco.com/modeling-labs/

When I worked at a regional ISP, my supervisor was the BGP wizard. He referred to exterior routing as "a black art". Even more, the telcos were deploying their own technologies like Frame Relay and SMDS, which are Layer 1/Layer 2 protocols beyond the standard "point-to-point" leased lines.

We once experienced a fiber cut on our T-3 backbone (construction workers didn't dial 811). So my supervisor arranged the BGP routes to send everything over a 56k line, IIRC. He gloated about it. The packet loss rate was absurd, but our customers had connectivity!

>When I worked at a regional ISP, my supervisor was the BGP wizard. He referred to exterior routing as "a black art".

Yep this seems like a very common experience. I tend to find most environments have one guy making BGP changes outside of project work.

>We once experienced a fiber cut on our T-3 backbone (construction workers didn't dial 811). So my supervisor arranged the BGP routes to send everything over a 56k line, IIRC. He gloated about it. The packet loss rate was absurd, but our customers had connectivity!

The modern version of this: At a small national ISP, we had our intercarrier lines cut. Megaport has this billing model where you only pay for the capacity you use, so our backup intercapital was a 1MB megaport service. Intercapital goes down, everyone kicks over to the megaport and we just log on to the megaport portal and raise the bandwidth to a few gig temporarily. Cost almost nothing to keep it sitting there ready for use. And yeah the engineer responsible was extremely and deservedly smug.

>And perhaps, vendors have simulators on a larger scale than the free downloads?

My experience is that you need both the exact hardware/firmware AND the exact config to perfectly simulate some of the weird and wonderful stuff. Largely because so much of the protocols issues, like the OP suggests, is down to individual vendor implementations of the protocol.

For instance, I used to consult for a small ISP that had a very unreliable peer. That peer would send them routes for everything, but occasionally their PE's routing plane would collapse and stop forwarding traffic to/from their other peers.

We still received enough packets to not trip any failover, and routes were still being advertised. So until they realised and rebooted their hardware, we had to withdraw our routes.

This is the specific behaviour between (IIRC) Cisco IOS-XR on our end, their predominantly mikrotik environment, and their other peers who I believe were mostly juniper.

I cant imagine simulating that without the relevant hardware and configs.

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