Subject: [bess] EVPN IRB - Clarifications on MAC/IP route with only the MAC address

From: Muthu Arul Mozhi Perumal <[email-masked]>
Date: Wed, 26 Jan 2022 13:39:07 +0530

Hi,

RFC9135 describes some scenarios where a PE withdraws a MAC/IP route with
only the MAC address if it had advertised such a route before. Here is one
such scenario:
<snip>
   On the source NVE, an age-out timer (for the silent host that has
   moved) is used to trigger an ARP probe.  This age-out timer can be
   either an ARP timer or a MAC age-out timer, and this is an
   implementation choice.  The ARP request gets sent both locally to all
   the attached TSs on that subnet as well as to all the remote NVEs
   (including the target NVE) participating in that subnet.

*The source   NVE also withdraws the EVPN MAC/IP Advertisement route with
only the   MAC address (if it has previously advertised such a route).*
</snip>

Have some questions:
1) If the source NVE had allocated MPLS Label1 on a per MAC basis, is the
source NVE expected to retain Label1 even after withdrawing the MAC/IP
route with only the MAC address? Otherwise, it would invalidate the MAC/IP
route with both the MAC and IP addresses since Label1 is mandatory and
expected to be valid in that route, right?

2) If the source NVE re-advertises the MAC/IP route with both the MAC and
IP addresses after withdrawing the MAC/IP route with only the MAC address,
say because of a route refresh request, should the re-advertised route
carry only the IP VRF Route Target?

3) Can the user assign the same route target for both the IP and MAC VRFs
and use it to match against both? RFC9135 does not explicitly prohibit, but
that may cause problems, for e.g. in #2 above, right?

Comments/clarifications would be helpful..

Regards,
Muthu