03-29-2022 03:59 AM
Hi
Current sertup is below
Hsrp running between sw and sw2
from sw1 and sw2 to edge switces are layer 2 and vpc running .
pic-1
pic-2
Now the idea is to change spine and leaf and layer 3
Currently vlans are span between in all the switches ( see the pic -1 )
Where will be the gateway of the servers , Is it possible to do all vlans in all leaf switches
Thanks
03-29-2022 04:58 AM
Hi there,
In a typical CLOS architecture the Layer3 boundary is pushed to the leaf switches. Servers will connect at Layer2 to the leaf switches and the this is where their local gateway will reside. Although you could reuse the same VLAN IDs across the leaf switches, you cannot share IP subnets. A prefix can only exist on one leaf switch. The spine and leaf switches will exchange routing information using eBGP and will implement ECMP.
Taking it a step further, you would expect to implement an overlay network in this architecture which would allow your tenants to span their Layer2 networks across the leaf switches between connected hypervisors, using VXLAN for example.
cheers,
Seb.
03-29-2022 07:11 AM
You can share the subnets and the gateway using VXLAN Anycast gateway... this is if your model of leaf supports the feature... but more importantly if your model of leaf supports the feature in ASICs.
The same gateway information will exist on all LEAF switches where the feature is running. Intra leaf routing decisions can remain local since the ARPs will not need to traverse the fabric to find the gateway or next hop. For any next hop that is not hosted on the leaf ARPs will work as normal.
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