[j-nsp] Overlay physical interfaces and Overlay next-hop

[Vincent Bernat]

They are from my Juniper SE. Maybe there is some KB explaining that, but
at the time, there was not.
-- 
Grief can take care of itself; but to get the full value of a joy you must
have somebody to divide it with.
		-- Mark Twain

-----Original Message-----
From: "Phan Thanh Tung (FPT Smart Cloud) via juniper-nsp" <juniper-nsp at puck.nether.net>
Sent: 24 mars 2021 09:01 GMT
Subject: Re: [j-nsp] Overlay physical interfaces and Overlay next-hop
To: Vincent Bernat; Phan Thanh Tung via juniper-nsp

> From: "Phan Thanh Tung (FPT Smart Cloud)" <tungpt15 at fpt.com.vn>
> Subject: RE: [j-nsp] Overlay physical interfaces and Overlay next-hop
> To: Vincent Bernat <bernat at luffy.cx>, "Phan Thanh Tung (FPT Smart Cloud) via juniper-nsp" <juniper-nsp at puck.nether.net>
> Date: Wed, 24 Mar 2021 09:01:58 +0000 (47 minutes, 31 seconds ago)
>
> I am quite interested in the formula that calculates the number of next-hops and interface-number you provide as reference.
>
> I would appreciate it if you could explain more clearly the parameters
> included in the above formulas corresponding to a specific context.
>
> -----Original Message-----
> From: Vincent Bernat [mailto:bernat at luffy.cx] 
> Sent: Wednesday, March 24, 2021 2:01 PM
> To: Phan Thanh Tung (FPT Smart Cloud) via juniper-nsp <juniper-nsp at puck.nether.net>
> Cc: Phan Thanh Tung (FPT Smart Cloud) <tungpt15 at fpt.com.vn>
> Subject: Re: [j-nsp] Overlay physical interfaces and Overlay next-hop
>
>  ❦ 24 mars 2021 03:25 GMT, Phan Thanh Tung (FPT Smart Cloud) via juniper-nsp:
>
>> Junos allows to re-allocate the maximum number of physical interfaces 
>> and the maximum number of next hops reserved for use in an Ethernet 
>> VPN-Virtual Extensible LAN (EVPN-VXLAN) overlay network.
>>
>> [edit forwarding-options]
>> vxlan-routing {
>>       interface-num integer;
>>       next-hop integer;
>>       overlay-ecmp;
>> }
>>
>> https://www.juniper.net/documentation/en_US/junos/topics/reference/con
>> figuration-statement/interface-num-edit-forwarding-options.html
>>
>> https://www.juniper.net/documentation/en_US/junos/topics/reference/con
>> figuration-statement/next-hop-edit-forwarding-options-vxlan-routing.ht
>> ml
>>
>>
>> I don't know how to determine how many overlay physical interfaces and 
>> overlay next-hop have been used.
>
> There is a first hard limit of 16k virtual ports but you should stay below 12k. Check with:
>
> request pfe execute command "show shim virtual vport" target fpc0 | count
>
> For next-hop, you can use:
>
> request pfe execute command "show nhdb summary" target fpc0
>
> This does not differentiate between next hops for VXLAN and next hops for the remaining. If you increase the VXLAN one, you decrease the remaining next-hops available by the same amount. On QFX 5110, the maximum is 45000 for both. On QFX 5120, this is 61000. So, if you can manage a safe margin for both next hops, you are fine.
>
> You can compute the number of next-hops manually with:
>
> - overlay: ARPs resolved via local IRBs ARP + Remote IRBs (number of
>   IRB per leaf*number of leaves) + Number of VRF with Type 5 * remote
>   VTEP with Type 5 + 1
> - underlay: 2 x Number of Layer-3 interfaces going towards each
>   spine + (Number of local-trunk-ports * number of vlans allowed on
>   each trunk port) + number of local access ports in each vlan + (Num
>   of Leaf-nodes – 1) * number of VLANs + 7
>
> For interface-num, this is the number of IRBs + number of routing-instances that have at least one active Type 5 tunnel.
>
> Note, that was 2 years ago. Juniper has internal documentations about that, so it may be better to ask JTAC for updates, notably an easier command to get the result may be available.
> --
> Use the fundamental control flow constructs.
>             - The Elements of Programming Style (Kernighan & Plauger)
> ----------
>
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