[c-nsp] IS-IS as PE-CE protocol

[adamv0025 at netconsultings.com]

> From: Oliver Boehmer (oboehmer) <oboehmer at cisco.com>
> Sent: Friday, March 22, 2019 10:35 AM
> 
>     Robert Raszuk wrote:
>     > Hi Victor,
>     >
>     > ISIS has analogy to OSPF down bit integrated if this was your question.
> 
>     Hopefully it is.
> 
>     > But
>     > do check with your implementation to make sure if it supports ISIS
> leaking.
>     >
>     > PE-CE ISIS is inheriting loop prevention which was defined for ISIS route
>     > leaking between levels in RFC2966
> 
>     Looks like it. Thank you for the hint!
>     >
>     > " This document redefines this high-order bit in the default metric
>     >
>     >    field in TLVs 128 and 130 to be the up/down bit."
> 
>     What would be the Cisco command to enable/disable this feature in IS-IS ?
>     That would be the easiest way to check if the implementation supports it.
> 
> Last time I checked (and it seems nothing has changed since) IS-IS can't run in
> a VRF, so you can't use it for MPLS-VPN PE-CE links.
> 
> IGP support on PE-CE links (like OSPF, EIGRP and RIP [sigh]) has been
> implemented to enable a seamless transition of typical Enterprise networks
> from L2 to L3-VPNs. And as ISIS is not a typical Enterprise IGP, it has not been
> top of mind..
> 
Bang on as always, even if on other vendors this stunt was supported, OP would be well outside the well-trodden path - expect dragons....

adam