Hi,
NLRI of an EVPN Type 2 route as described in Section 7.2 of the 7423bis
draft<https://datatracker.ietf.org/doc/html/draft-ietf-bess-rfc7432bis-04#section-7.2>
includes two optional fields:
* IP address. Presence or absence of this field is indicated by its Length
(a mandatory field in the NLRI). If this field is absent, the route is
frequently referred to as MAC-only
* Label2. To the best of my understanding its presence or absence is
inferred from the Length of the Type-specific part of the NLRI.
These two optional fields are separated by a mandatory field Label1.
Neither the draft nor the original RFC7432 do not say whether Label2 field may
be present in the NLRI of a MAC-only route.
The situation as I see it is ambiguous because:
1. AFAIK as of this moment usage of the Label2 field is only defined in RFC
9135 in conjunction with Symmetric EVPN IRB and only for routes that include
both MAC and IP addresses
2. At the same time advertisement of MAC-only EVPN Type 2 routes that
include Label2 field is not explicitly prohibited
3. My colleagues and I have encountered at least one implementation that
treats an NLRI if a MAC-only EVPN Type 2 route that includes Label2 field as
malformed.
A clear-cut answer, one way or another, would be most helpful.
Regards,
Sasha Vainshtein
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