Subject: [bess] Question on IRB MAC in draft-ietf-bess-evpn-inter-subnet-forwarding

From: Muthu Arul Mozhi Perumal <[email-masked]>
Date: Tue, 19 Mar 2019 16:00:35 +0530

draft-ietf-bess-evpn-inter-subnet-forwarding describes two ways of
provisioning the default gateway MAC and IP addresses on the IRB interface
associated with the corresponding subnet:

<snip>
   1. All the PEs for a given tenant subnet use the same anycast default
   gateway IP and MAC addresses . On each PE, this default gateway IP
   and MAC addresses correspond to the IRB interface connecting the BT
   associated with the tenant's VLAN to the corresponding tenant's IP-
   VRF.

   2. Each PE for a given tenant subnet uses the same anycast default
   gateway IP address but its own MAC address. These MAC addresses are
   aliased to the same anycast default gateway IP address through the
   use of the Default Gateway extended community as specified in
   [RFC7432], which is carried in the EVPN MAC/IP Advertisement routes.
</snip>

Further below it says:

<snip>
   Irrespective of using only the anycast address or both anycast and
   non-anycast addresses on the same IRB, when a TS sends an ARP request
   or ND Neighbor Solicitation (NS) to the PE that is attached to, the
   request is sent for the anycast IP address of the IRB interface
   associated with the TS's subnet and the reply will use anycast MAC
   address (in both Source MAC in the Ethernet header and Sender
   hardware address in the payload).
</snip>

In the above, it says the ARP response or NS will use the anycast MAC
address. The question is, how is this feasible if the second option of
provisioning
the default gateway MAC and IP addresses on the IRB interface are chosen,
where each PE for a given tenant subnet uses the same anycast default
gateway IP address but its own MAC address?

Should it instead say:
  the request is sent for the anycast IP address of the IRB interface
   associated with the TS's subnet and the reply will use *configured*
   MAC address?

i.e. s/anycast MAC/configured MAC?

Regards,
Muthu

---

From: Muthu Arul Mozhi Perumal <[email-masked]>
Date: Tue, 26 Mar 2019 11:27:41 +0530

Hi authors, EVPN experts,

Any feedback?

Regards,
Muthu

On Tue, Mar 19, 2019 at 4:00 PM Muthu Arul Mozhi Perumal <
[email-masked]> wrote:

> address. The question is, how is this feasible if the second option of provisioning