Re: [IPFIX] ipNextHopIPv6Address reported address

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> On 04 Jun 2015, at 13:07, Nick Brown <[email protected]> wrote:
>=20
> Hi All,
>=20
> In a sentence, is it expected that ipNextHopIPv6Address should report
> the global ipv6 address of the next hop when it has one, or may the =
link
> local address be reported instead?
> http://tools.ietf.org/html/rfc5102#section-5.7.3

First, the proper reference for the definitions of IEs in the IPFIX =
information model is http://www.iana.org/assignments/ipfix/ipfix.xhtml; =
per 7012, 5102 is no longer considered authoritative for IE definitions.

(In this case, though, this is an admittedly pedantic distinction; the =
content is identical).

> There are obvious cases where the next hop may only have link local
> address, if example it's only configured that way. But in other cases
> where it may have both a link local and global address it's often the
> case that routing protocols may use local addresses to setup the
> forwarding plane where traffic is being observed. Thus at the point in
> the forwarding path that traffic is being observed this all that is
> available, and it's not apparent that a mapping from link local =
address
> to global address (where is exists) can be done.

The way I read this, if the address is not being changed as part of the =
packet handing (on which see the fifth point in section 2.3 of RFC =
7012), the address to report is the address the packets are sent to in =
the context of the egress interface. If the connection between the =
device the MP is on and the next hop has link-local addresses only, then =
the link-local address is the correct one to export.

Cheers,

Brian

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