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ROUTING QUESTION: PI and PA IP addresses on the same ASN
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ROUTING QUESTION: PI and PA IP addresses on the same ASN

elos42elos42 Member
edited March 2020 in General

I am on a particular host which has a global footprint and thousands of physical servers.

It has both PI and PA IP addresses, its own global ASN and also many IP subnets that are allocated to this hosting provider. It does not use any IP address space that is not 'in its name', either through 'Direct Allocation', 'Allocated PA' or 'Legacy'.

Needless to say, its network is multihomed.

According to theory, the routing table for PA ip address spaces are linked to the routing table of its parent, grandparent etc.. in a hierarchical way all the way up to the /8 provider.

Routing tables for PIs are separately 'fed' into routers (needs to be at least /24 or a block of 256 IP address for this to be accepted).

My question is -- suppose I take a PA (provider aggregatable) IP address from this hosting provider, who exactly is the 'provider' in this case? Is it this hosting provider, given that it 'owns' its IPs, has a global network, and is multihomed (gets upstream from a dozen providers at various parts of the globe, though some locations seem to have only one upstream provider.)

Or does this hosting provider's IPs get aggregated by particular ISPs based on the priority given to the upstream connection for that IP in that IPs routing table (based on BGP)?

The reason I'm asking this question is that I'm seeing some difference between PI and PA IPs on this providers' network, even though I would have assumed that since it's such a huge player, it would be its own provider and therefore PA and PI would essentially work the same?

Also, is it true that the only true Legacy spaces (as in PI and all that) are with RIPE and ARIN, and others like APNIC have converted legacy spaces to PAs, for purposes of routing?

Comments

  • ClouviderClouvider Member, Provider

    From the BGP routing perspective it’s irrelevant whether the IP is PA or PI. This terms are only relevant to the policy.

    Clouvider Limited - Leading Hosting & Connectivity Partner || Dedicated Server Sale from £39/m - Our Latest LET Offer

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  • What would explain the differences seen in routing.. I'll give an example. There's a smallish mobile operator in India, and if one tries to reach one of the major cloud providers' singapore DC from this operator, the route is via Europe for PA and direct for PI. There's no such issue for other mobile operators. But this issue is there for multiple cloud providers (and their various IP series) from this particular mobile operator. My guess is that this operator seems to rely on some kind of provider-based routing and when it's a PI address, it gets its value from somewhere else. Strangely enough, in this case, it's the PI that gives it the correct (short) route.

  • ClouviderClouvider Member, Provider

    No, the status of the space is irrelevant from the point of routing. Each subnet can have a different inbound route. Each router can have a different outbound route. The internet is not symetric.

    Thanked by 1yoursunny

    Clouvider Limited - Leading Hosting & Connectivity Partner || Dedicated Server Sale from £39/m - Our Latest LET Offer

    Cloud Web Hosting | SSD & SAS HA OnApp VPS | US, UK, NL & DE Dedicated Servers | Network Services | Colocation | Managed Services

  • Pi IP address? And I thought writing out IPv6 IP's was a hassle.

  • elos42elos42 Member
    edited March 2020

    What's interesting is a case like Vultr. They have several subnets in Singapore, all under their own ASN, and allocated either to Choopa or reassigned to Vultr.
    But some of the series have a direct route from this mobile operator, while others are routed via LA. I won't be surprised if some others are routed via Europe too.
    Unfortunately, when you optimize for one network, things start falling apart for another mobile operator.

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