dc -design help

[bluesea2010]

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

[Seb Rupik]

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.

[sp2720401]

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.