Hi Yubao,
Thanks for your email. Yes, you misunderstood the use-case 😊 but these are good
questions, we will clarify in the next revision.
1. The IP Prefix routes are advertised with the ESI and always a zero-GW-IP.
* Three co-authors of this draft are also co-authors of
draft-ietf-bess-evpn-prefix-advertisement and the latter explicitly prohibits
the use of non-zero ESI and non-zero GW-IP simultaneously. So you will not see
the use of the GW-IP in draft-sajassi-bess-evpn-ip-aliasing.
* In fact that is also one of my comments for
draft-mackenzie-bess-evpn-l3aa-proto-00: using non-zero ESI *and* non-zero
GW-IP in the IP Prefix routes is non-backwards compatible and will break
interoperability with existing RRs. But I will send a separate email with my
comments.
1. About the use-case of slide 7:
* As mentioned, the (virtual) ES is associated to the VNF loopback, i.e.
1.1.1.1, and its operational state is tied to the reachability of that loopback.
* On leaf-1/2/3/4, the reachability of the loopback is determined by a
static-route or IGP, and can be used along with BFD to speed up fault detection.
* As an example, suppose leaf-2 has a static-route to 1.1.1.1 with
next-hops {20.0.0.1,20.0.0.2,20.0.0.3}, and 1.1.1.1 is associated to ES-1.
i. The ARP resolution to those next-hops is done as
usual, nothing especial, it’s done as soon as the static-route is added.
ii. ES-1 will be oper-up as long as the static route is
active in the IP-VRF route-table. When it goes inactive, ES-1 will go down and
the AD routes withdrawn.
iii. Obviously, and individual AC going down in leaf-2
will not make the static-route inactive, hence will not bring down the ES. The
IRB going down will make the static-route inactive, hence the ES will go down.
* A similar example would work with an IGP instead of a static route to
1.1.1.1.
I think that should clarify your questions.
Let me know otherwise.
Thanks.
Jorge
From: [email protected] <[email protected]>
Date: Wednesday, July 28, 2021 at 12:14 AM
To: Rabadan, Jorge (Nokia - US/Mountain View) <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Comments on draft-sajassi-bess-evpn-ip-aliasing-02
Hi Jorge,
This is the detailed explanation of the question I asked in the IETF 111
meeting.
In page 7 of
slides-111-bess-sessa-evpn-ip-aliasing<https://datatracker.ietf.org/meeting/111/materials/slides-111-bess-sessa-evpn-ip-aliasing-00>,
when leaf-5 send traffic to leaf-2, how does leaf-2 find the corresponding
ARP entry for 20.0.0.2 or 20.0.0.1 or 20.1.1.3 ?
I guess the GW-IP 1.1.1.1 will be advertised as overlay index along with the
ESI.
But the draft-ietf-bess-evpn-prefix-advertisement-11 does not define an IP
Prefix Advertisement Route with both GW-IP and ESI both as overlay index.
I suggest that this should be updated if you want to do so.
And the preference of ESI overlay index should be considered higher than GW-IP
overlay index for Leaf-5's sake.
But the preference of ESI overlay index should be considered lower than (or
maybe they should both be used? ) GW-IP overlay index for Leaf-2's sake
These are new rules that can't be found in
draft-ietf-bess-evpn-prefix-advertisement-11<https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-prefix-advertisement-11#section-3.2>
.
But on the contary, if the IP Prefix Advertisement Route has a GW-IP overlay
index,
It can support the same protection procedures without any ESI overlay index.
( The details to do such protection using GW-IP overlay index I have described
in
draft-wang-bess-evpn-arp-nd-synch-without-irb-06<https://datatracker.ietf.org/doc/html/draft-wang-bess-evpn-arp-nd-synch-without-irb-06>.
)
So I don't get the point why we need two redundant overlay index?
Can you clearify it?
Maybe an IP Prefix Route Style with a GW-IP overlay index is engough here.
And such Route Style is in compliance with
draft-ietf-bess-evpn-prefix-advertisement-11<https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-prefix-advertisement-11#section-3.2>
already.
Another question is that: If the ESI overlay index is advertised, when will the
IP A-D per EVI route of Leaf-2 be withdrawn?
When the IRB interface on Leaf-2 fails?
When one of the three ACs fails?
When all of the three ACs fails?
If you want to do so, I suggest that the ESI-1 to be configured onto the IRB
interfaces,
But in Figure 2 of
draft-sajassi-bess-evpn-ip-aliasing<https://datatracker.ietf.org/doc/html/draft-sajassi-bess-evpn-ip-aliasing-02#section-1.3>-02,
I see the ESI is configured on the ACs of the BDs.
Is anything I have misunderstood?
Best,
Yubao
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