I came to your blog post http://blog.igics.com/2014/05/dell-force10-vlt-virtual-link-trunking.html and I am really happy that you shared this information with us. However I was wondering if you have tested a scenario with 4 S4810 with VLT configured on 2 x 2 and connected together (somewhere called mLAG). How do you continue to add VLT couples to the setup? I would be really happy if you could provide any info regarding such setup.
If you are not familiar with DELL Force10 VLT technology read my previous blog post where is VLT described in detail. It is really important to understand VLT before you try to understand mVLT (Multi-domain VLT). By the way mVLT is called eVLT (Enhanced VLT) in Force10 documentation so it might be little bit confusing. Anyway mVLT is nothing else then regular virtual port channel (VLT) between two VLT domains. Therefore mVLT is quite good term if you ask me.
However we would like to have hardware and link redundancy therefore multi chassis port-channel technology (Force10 VLT in our particular case) is used to still have simple loop free topology from spanning tree point of view but with switch unit and physical link redundancy. Force10 mVLT solution is logically depicted on figure below.