Provider aggregated vs Provider Independent IP Addresses - Use case

[nwekechampion]

Hi Guys,

I am looking for some info regarding the usage PI and PA addresses.

What are the use-cases?

When would it be advisable to use one?

How does it affect BGP?

Do ISP clients still need to be on a different AS if they have a PA address?

Appreciate some feedback.. thanks guys

[nwekechampion]

Thanks Joseph makes sense now.

[Kanan Huseynli]

Hi,

when you get IP from provider, it is PA address for you and PI address for your ISP. ISP normally (mostly) owns the scope and authorizes to advertise that scope to global internet from its AS. That's the reason, when you change ISP, you have new IP range.

PI is your owned IP scope and you have authorization to advertise it to global internet (through providers) and control on it.

For example, you have 2 ISPs. If you get scopes from ISPs then these are PA scopes for you. Even if you have BGP and you advertise them, you are not allowed to advertise provider A scope to provider B. So, any external application fails if you bound it to one public IP address.

But if you have your own scope (PI), you are allowed to advertise this scope to any ISP and in case of failure, for example, traffic still works over the second ISP.

[Joseph W. Doherty]

Just want to mention what @Kanan Huseynli describes is the norm, but can be actually done depends how cooperative your ISPs are and their cooperation often is tied to $$$.

BGP is very flexible.

The "Internet" is comprised of private networks which have, more or less, full control over how they interact with each other.

[MHM Cisco World]

at which point you confuse ?