[j-nsp] EVPN-VXLAN: Mixing QFX and EX

[Vincent Bernat]

 ❦ 16 avril 2019 17:32 +00, Ian <i2vanov at protonmail.com>:

> Much appreciated reply.
>
> My understanding is EVPN-VXLAN uses anycast on all spines. All spines
> would have the same IP address (that is the gateway IP). Considering
> the limitations of the EX4600 you pointed out (which I assume is due
> to the Broadcom chipset), means in a case of mixing EX4600 with
> QFX5110, then the routing between VXLAN could only occur on the spines
> (assuming a QFX5110 or similar model supporting this) which
> effectively means traffic would trombone back and forth from the
> leaves to the spines rather than remain local to the switch even if
> the servers are on neighboring physical ports on the EX4600 leaves.
>
> Am I making right assumptions?

It depends on how you assign subnets to each leaves. For example, if
each leaf gets its own subnet, local traffic would be L2 only and stay
on the EX4600 leaves. On the other hand, if you assign two different
subnets, routing between them will require the traffic to go to the
spine, even if the source and destination are attached to the same leaf.

Also, note that if you plan to use QFX5110 as edge for your VXLAN
network, you may run into the following limitation:

(QFX5110 switches only) By default, routing traffic between a VXLAN and
a Layer 3 logical interface—for example, an interface configured with
the set interfaces interface-name unit logical-unit-number family inet
address ip-address/prefix-length command—is disabled. If this routing
functionality is required in your EVPN-VXLAN network, you can perform
some additional configuration to make it work. For more information, see
Understanding How to Configure VXLANs on QFX5110 Switches and Layer 3
Logical Interfaces to Interoperate.

<https://www.juniper.net/documentation/en_US/junos/topics/concept/vxlan-constraints-qfx-series.html>

It means a QFX5110 is not able to route between a family inet interface
and a family ethernet-switching interface when it implies doing VXLAN
encapsulation/decapsulation. QFX10k is able to do that without any
issue. Juniper provides a documented workaround, but it's quite recent.
-- 
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