On 22/11/2021 15:00, Robert Raszuk wrote:

    it's not a choice, that is an MPLS architectural requirement and it
    happens in every single SP network that offers services on top of MPLS.
    If that is considered architecturally incorrect, then the whole MPLS
    would be. But regardless of that, it has been used very successfully
    for
    last 30 years.


No. Please read RFC5283.

and how many SPs have deployed it?

Hardly any, and maybe because of what is described in section-7.2

"For LER failure, given that the IGP
 aggregates IP routes on ABRs and no longer advertises specific
 prefixes, the control plane and more specifically the routing
 convergence behavior of protocols (e.g., [MP-BGP]) or applications
 (e.g., [L3-VPN]) may be changed in case of failure of the egress LER
 node."


And what RFC5283 suggests in the same section is:

    "Advertise LER reachability in the IGP for the purpose of the
     control plane in a way that does not create IP FIB entries in the
     forwarding plane."

Above defeats the prefix aggregation.


Peter



Thx,
R.

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