Re: [bess] FW: Regarding the Alias label usage in EVPN Multihoming

[Muthu Arul Mozhi Perumal <[e-mail]>]

My understanding:

For the single-active case in the diagram below, when PE4 receives the A-D
per ES route withdraw it won't know whether PE2 or PE3 will become the new
primary/DF for the <ES, VLAN>, so it will start flooding the traffic
destined to MAC1. Then either PE2 or PE3 will become the new primary/DF for
the <ES, VLAN> and advertise the MAC/IP route for MAC1. PE4 will then start
sending the traffic destined to MAC1 to the new primary.

For the all-active case, when PE4 receives the A-D per ES route withdraw it
will update the nexthop list for MAC1 by removing PE1 from that list. PE4
will then load balance the traffic destined to MAC1 by send it to PE2 and
PE3 using alias label.

Regards,
Muthu

On Wed, Mar 6, 2019 at 7:51 PM Luc Andre Burdet (lburdet) <[e-mail]>
wrote:

> Hi Chalu,
>
>
>
> Please read 7432 s.8.4: in single-active it is not an aliasing
> label/procedure but a backup-path procedure.
>
> It will answer your questions (both, actually).
>
>
>
> There is no flooding once the MAC is learnt & distributed: cf. that’s the
> point.
>
>
>
>
>
> [image:
> http://www.cisco.com/c/dam/m/en_us/signaturetool/images/banners/standard/09_standard_graphic.png]
>
> *Luc André Burdet*
>
> [e-mail]
>
> Tel: *[phone]*
>
> Cisco Systems Canada Co. / Les Systemes Cisco Canada CIE
>
> Cisco.com <http://www.cisco.com/web/CA/>
>
>
>
>
>
> *From: *BESS <[e-mail]> on behalf of chalapathi andhe <
> [e-mail]>
> *Date: *Wednesday, March 6, 2019 at 04:15
> *To: *"[e-mail]" <[e-mail]>
> *Cc: *Sean Wu <[e-mail]>, Jaikumar Somasundaram <
> [e-mail]>, "[e-mail]" <
> [e-mail]>
> *Subject: *Re: [bess] FW: Regarding the Alias label usage in EVPN
> Multihoming
>
>
>
>
>
>
>
> Hi All,
>
>
>
> Can you please help us on the following issue.
>
> In the following diagram, PE1, PE2, PE3 are connected to the same ES [ES1]
> in Single active mode, and PE4 is a remote PE.
>
> Let’s say PE1 is advertising the MAC1 route, PE4 will install the MAC1
> with the PE1 as primary path with MAC Label,
>
> and PE2, PE3 as backup with the Alias Label. Now if the PE1 to CE1 link
> goes down, then PE1 withdraw the EAD/ES route
>
> which will be processed by PE4.
>
> Now what should the forwarding state at PE4 ?, PE4 should update the
> forwarding state of MAC1 with the PE2, PE3 Alias label
>
> and any traffic destined to MAC1 should be flooded to PE2, PE3 with the
> Alias labels ?
>
> Or packet should be flooded to PE2, PE3 with the Flood labels ? Or should
> it be some other method ?
>
>
>
> In similar if the ES is operating in all active mode, what should be the
> forwarding state at PE4 ?
>
> PE4 should update the forwarding state of MAC1 with the PE2, PE3 Alias
> label
>
> and any traffic destined to MAC1 should be sent to either PE2 or PE3 with
> the Alias labels [ not flood to both] ?
>
> Or packet should be flooded to PE2, PE3 with the Flood labels  or Alias
> Label ?
>
> Or should it be some other method ?
>
>
>
>
>
> [image: cid:1695247dcc04ce8e91]
>
>
>
>
>
> Thanks,
>
> Chalapathi.
>
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