HI Linda: Collisions in unmodified VM administered tags IMO cannot be avoided which if left along would result in the problem you describe. But that is what S-tags are for. Network administered tag value inferred from customer tag information. When mapping into a larger network (e..g S-tag->I-SID), the S-tag can still retain local significance. Hence the only limitaton is if there is a requirement for more than 4094 VLANs at a local attachment point to the larger network. The network itself can scale to the full 2**24 tags.
cheers Dave ________________________________ From: Linda Dunbar [mailto:[email protected]] Sent: Tuesday, July 31, 2012 11:16 AM To: David Allan I Cc: [email protected] Subject: RE: You presentation on VM mobility... David, In the absence of VM mobility, it is easier for Overlay network to make the 12-bits VID locally significant by using core's 24 bits ID (VNID) to provide >4K's isolation. When applications (e.g. firewall) sit on multiple subnets, those VMs Guest OSs do send VID encoded data frames. When those VMs move, the same VID used by the VMs will appear in different NVEs, making those 12-bits VID globally significant. Linda From: David Allan I [mailto:[email protected]] Sent: Tuesday, July 31, 2012 12:45 PM To: Linda Dunbar Cc: [email protected] Subject: You presentation on VM mobility... HI Linda: You said that even with a 24 bit tag in the core, VM mobility would make it difficult to genuinely achieve more than 4K VLANs.... I have to admit that flies in the face of my understanding of both tagging and scaling. Could you clarify WHY you believe this to be true? Much thanks Dave
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