MicroNugget: BGP Configuration Explained | CBT Nuggets

In this video, CBT Nuggets trainer Keith Barker provides a brief overview of how the Internet works together with BGP (Border Gateway Protocol), and how BGP chooses the best route when presented with multiple paths. Learn more about how BGP works to get started on BGP configuration.

We can all give thanks to BGP, which makes important forwarding decisions to choose routes, for the entire Internet.

This happens because entire clouds of networks receive autonomous system numbers (ASNs), and get addresses distributed amongst them.

The Internet Assigned Numbers Authority is responsible for managing all the IPv4 and IPv6 addresses. Regional Internet Registries handle the many requests that are generated by service providers to gain additional addresses.

With those blocks of addresses, enterprises can subnet and rent them out to customers. After a company takes those addresses and makes those routes and subnets, BGP comes in to advertise the routes to neighbors.

Those advertisements get propagated across the entire Internet. But when an AS learns that there are two different routes to get to a given network, it has to determine its path.

Fortunately, the address itself includes how many hops were necessary to reach the end. So the router just has to choose the one with the fewest hops.

0:20: An overview of what BGP does and how it chooses its routes
1:30: The relationship between IANA and RIR
2:35: BGP's job advertising routes
3:40: How BGP chooses a route between options
4:55: Live demonstration of the determination process

Start learning with CBT Nuggets:

[EViL]

8 years old... and still the best video I managed to find on this! Great job, thanks!

[vuttham]

11 yrs old video, but still it's the best to video to all the network engineers who just lost their basics and also the best video to all the novice network engineers.

Great Job Keith.

[KeithBarker]

You are very welcome. Thanks for your kind words.

Best wishes,

Keith Barker

[muhamj]

Keith Barker always makes things easy to understand. I really enjoy his style.

[xfox]

Thanks for the easy brief introduction to BGP, still one of the best vids out there.

[abrahamoz]

Thank you very much Keith, great BGP intro video it makes a lot more clearer now... :))

[ardentdfender]

This is so well explained and explained by Keith. Well explained for me and impending CCNA exam. Very relevant in age of FB down earlier this week.

[MyJonathanAlex]

Keith you are the man...thanks for putting this out there...simple and clear..you rock.

[dhhsncnd]

Keith's vids are always inspiring. I wish he has more detials for BGP in his personal channel.

[fieldzee]

This is the best video I've seen to explain how this works. I am a visual learner, so this works for me.

[francescogalli]

Simply love this channel✌🏻
As junior networker, it's my Bible 🏅

[SkynetWanoGth]

I Love Keiths teaching style he is the best

[KennyBentley]

Excellent video! I'm studying for some IT certifications and have learned a lot about TCP/IP on a LAN, but I've been curious about how it works on the Internet. Thanks for sharing.

[ryanmyers]

Absolutely great video, explained very well easily understood, Way better then the classroom....

[KeithBarker]

Hello- Great question.

If all the items up to and including the AS hops are equal, the following would be used, in this order:

lowest ORIGIN type (IGP, EGP then Incomplete, in that order)

if that is a tie then

lowest MED

if that is a tie then

eBGP over iBGP learned path

if that is a tie then

lowest IGP metric to the next hop

and there are a few more if those are tied as well.

Before the AS hops, there are a few checks it also does.

Hope that helps,

Keith

[karimaurelie]

allways simple to understand with you
thanks a lot

[TotemYuri]

thank you for the video, very helpful!

[rOnNiecHaRles]

PLEASE TEACH US MORE LIKE THESE, ONCE I GET HIGH SALARY I WILL ENROLL TO YOU CBT NUGGETS I PROMISE THAT!

[KeithBarker]

The router can recursively figure out the correct next immediate hop, to reach the BGP peer who sent the packet, based on its routing table and will forward it based on that. If MPLS is used, label switching could come into play, but that is another story altogether.

[pjtemplin]

MED is (normally) only a factor when there are multiple links from one AS to another AS, and your question only applies if the routers within one AS are running vastly different software versions so as to pick different favorites. The "incomplete" is merely an origin code, not an incomplete ASN.