However my post is primarily focused on the issue of "wasting" VLANs (scarce resource) for a function that has no real usage of VLAN and L2 switching whatsoever and its negative impact in real life use cases.Īccepting and taking into consideration all the facts around 元VNIs and symmetric/asymmetric IRB, i still find it unnecessary and kind of "arbitrary" to "waste" a VLAN for each 元VNI/VRF/Tenant. Thanks for your reply, indeed it is helpful and brings additional clarity to the subject at hand. If that info makes sense let me know, if not ill try and clarify more. Ok I rambled on a bit there and maybe slightly incoherently. I suspect this design will change in the future because switch asics are no longer designed with constrained limits any more and technically could use bridge domains, but right now they are locked into using vlan ids probably due to BU stuff or just because that is what everyone is used to at the moment. That is basically what it is doing so it can differentiate between routed and non routed. That works fine on layer2 right, now you have another physical port connecting the two switches, but instead it's a router port with ip address x.x.x.x on both sides. Say they are connected with a trunk port and allowed vlan 50-100. You can picture it like if the two switches were directly connected without using evpn or vxlan at all. Because vxlan is layer2 only, this tells it that it needs to do a routing lookup.Įxample, you have a server on leaf1 and it uses anycast gw to get to server on leaf2 (two different subnets), the anycast gw mac address will be where the server sends the traffic to default gw (the anycast gw mac), this switch will do routing lookup and see the nexthop is leaf2, this nexthop has to be an adjacency, which is formed by the association from the other vtep which is advertising the information over EVPN, the egress encap db gets populated with the tunnel info and nexthop of the other device. Every device does independent routing lookups. It has to know whether or not to forward the frame on layer2, or do a routing lookup on it. Think of the vlan as a bridge group, an endpoint, where on routers you could have tens or hundreds of thousands but switches are limited. Respectively if the frame is destined to the 元 VNI (mapped to another vlan endpoint of course) and the destination MAC address is the address of the router (the SVI/IRB int) then it must do a layer3 lookup to perform routing locally. so for example if the VTEP receive a frame and it's destined to L2 VNI which is mapped to vlan endpoint, it knows to do a lookup in the MAC table for this frame and send it out. Switches only have space for the 4k vlans in their table and the IRB interface (SVI) uses one of these targets.Īlso, VTEP need to know whether or not to perform a l3 lookup on the received vxlan encapsulated frame. They don't use vlans as much as pushing a popping tags so the 4k vlan limitation is not there). If it's a router it can use a different target (routers have much higher capability of interface targets i.e. The reason it needs a vlan is because it's a switch. So the nexthop of the routing part is to the vrf, which needs a mac address as a nexthop since vxlan is layer2, and the device provides that by using a vlan interface and vlan id. But you are not especially good with details you need others to help you deal with the smaller parts of the picture.The reason is because vxlan is layer2 only, and to use layer3 the routing needs a destination/nexthop. In general, you also see the methods necessary to fulfill that promise. You dream of big projects, great undertakings, and rewards. “You want success in its fullest meaning - wealth, power, and material comforts. You are a realist and a visionary planner.” Inner analysis of Querious by heart number 8 You are highly competitive and will not rest until you are satisfied that you have bypassed the opposition. Whatever your enterprise, you strive to be the best and most successful in your field. It is both your challenge and your birthright to gain dominion over a small part of the earth. “You have the power and potential to achieve great things. Talent analysis of Querious by expression number 8 Querious name personality by numerology Numerology (Expression Number)
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