Posts tagged “networking”

CCNA 200-301

Last update: 2021-06-25.

Tags: networking, cisco

Today I passed Cisco's CCNA 200-301 certification exam. In short, they fixed a lot of old problems but added a few new ones. However, it's still much closer to an exam that a working network administrator can walk into from the street and pass, compared to the last time I've seen it. In this post I'll try to offer some preparation tips.

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Anycast routing

Last update: 2018-02-28.

Tags: networking, bgp

It is well known that due to limited practical size of a UDP packet that can be transmitted without fragmentation, the number of DNS root servers is limited to 13 addresses. There are indeed 13 root servers named from A to M (a.root-servers.net, b.root-servers.net and so on). However, if you visit root-servers.org, you can see that most of those servers somehow have dozens and even hundreds locations around the world. How is it possible for one server to have more than one location? The answer is anycast routing.

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