Load-balancing From Single Transport to multi-transport Setup.

[Yashmit]

Hello Guys ,

Could you please help me to clear below doubts ?

[      ]                                                                             T2[      ]
[VE1]T1-------<<<PULBLIC-INTERNET>>============[VE2]
[      ]                                                                             T3[      ]

1)TLOC Color Restrict not used

2) Full Meshed Topology :- Two tunnel from VE1 to VE2 (T1-T2 & T1-T3) and vice versa (T2-T1 & T3-T1)
2) No Central policy used

Q1 : Will VE1 use ECMP to perform Load-balancing over both tunnels or only used one tunnel ?

As per my understanding it will use EMCP for both Tlocs and will perform load-balancing over both tunnels but
I am having a doubt like what is the purpose of load-balancing over single underlay Transport.
Logically all traffic will be carry over single transport.

Q2 : same as above question , will VE2 perform load-balancing over both tunnel for single Tloc ?

B.R.
Yash

[Kanan Huseynli]

Hi

A1: what do you mean by single transport? Normally, in this type of design you have 2 different ISP connections on VE2. In reality, especially for SD-WAN this is actually 2 transport (internet1 and internet2) for VE2. Thus, 2 tunnels are created and makes 2 path.

In any case, without policy router does ECMP by default, if you need preferred-backup paths, configure policy.

A2: As mentioned, technically you have 2 tunnels. Both routers will do ECMP

HTH,

[Yashmit]

Hello Kanan ,

First of all Thanks for your reply.

Let me clear the case.

There are two sites suppose A & B .

On site A we have V-edge router [VE1] with  single Transport Link says internet (Public Color : public-internet) and TLOC : T1

On Site B we also have V-edge router [VE2] with two internet Transport Links (Public Colors : public-internet & Biz-internet  ) and respective TLOCS (T2 & T3).

B.R.

Yash

[Kanan Huseynli]

Thanks. So, I understood correctly when I wrote the first comment. You have 2 tunnels with respect to both routers. For VE1 one interface-one underlay, but in reality it uses to tunnels to reach VE2. So, ECMP happens.

regards,

[Yashmit]

Hello Kanan ,

I would like to re-phrase the question/concern.

As per my understanding , Viptela consider OMP route with TLOC as a path (suppose route x.x.x.x with Tloc T) not a tunnel , so when we talk about ECMP (equal cost multi path) , It mean two or more OMP path with equal cost.

In our case , Site A will receive two Path , let say x.x.x.x with Tloc T3 and x.x.x.x with Tloc T2 from Site B, so here EMCP will do Load-balance .

But on Site B , router will receive a single path (y.y.y.y with Tloc T1) so here ECMP should not work , it will picked any Tunnel with the help of Hashing.

B.R.

Yash

[Kanan Huseynli]

Hi,

yes, advertised OMP route and TLOC route will be one, but to reach that TLOC you have two interface. This is like in traditional networks where you have remote BGP neighbor that advertises route (one router, one route, one next-hop IP), but to reach that remote next-hop you may have multiple paths via running IGP (ospf,eigrp whatever). Hence, it results two paths actually and router does ECMP over interfaces. This is the same in SD-WAN too. As you said, router picks interface using hashing. This is ECMP ,in reality, isn't it?)

I have looked CVD as well. Cisco uses the term "tunnel" while talking about ECMP.

https://www.cisco.com/c/en/us/td/docs/solutions/CVD/SDWAN/cisco-sdwan-design-guide.html#EqualCostMultipathECMPforTunnels

regards,