Is it possible to create BGP on LAN

@ReneMolenaar @lagapides

I have a quick question!
Can we implement BGP on a LAN?

Thanks in advance!

Best Regards,
-Akshay.

Hello Akshay

It is possible to implement BGP on a LAN. However, it is not at all desirable. There are many reasons why, but probably the most important one is convergence time.

Internal Gateway Routing Protocols (IGRPs) such as EIGRP, OSPF and RIP are designed for comparatively fast convergence. This means that if a router goes down within your network, typically routing will be restored (assuming an alternative route exists) within dozens of seconds. BGP typically has a network rerouting time exceeding 3 minutes. This of course can be tweaked, however, for typical internal networks, IGRPs are always your best bet.

If you are Microsoft or Cisco and you have a huge worldwide corporate network, you may want to employ BGP between your sites, however, internal routing will always be IGRP for the vast majority of networks.

I hope this has been helpful!

Laz

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It really depends. There’s a use-case for everything. A friend of mine works for Oracle Cloud and they deploy BGP on their LAN because it allows for very granular control of advertisements. As everything is already redundant, no one cares about high convergence time. My friend and I were surprised to see this, but it works really well.

When I worked for an ISP we deployed BGP between all our edge routers and used BFD with 300 ms timers to detect link flap over circuits. That allowed for very fast (sub-second) convergence time in BGP. So again… it depends.

As a general rule of thumb, I don’t deploy BGP for customers unless I’m peering with an ISP or a cloud service such as Azure.

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Hello Richard

Thanks for your contribution. As usual, there are always exceptions to rules of thumb. There are always situations in which best practices can be overlooked and put aside in favour of solutions that may not be conventional, but they work. How do we know? As you mentioned, from use cases, from experience. A best practice should not stand in the way of getting things done in a better way for specific and specialized cases.

Thanks for that!

Laz

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