Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
An excellent question!
Perhaps one of the biggest drivers for going back to L2 has been virtual servers that can logically migrate from one part of the network infrastructure to another.
Consider a host, even perhaps a user host, that's wired into your network. Once that host is on-line, if I repatch it to another port, same VLAN/subnet, it usually will resume operation, on the network, with little fuss. Its MAC remains the same and its IP remains the same.
If I repatch the host into a different VLAN/subnet its MAC remains the same but it will need a new IP (DHCP for a server?). The latter, different IP, is what causes issues, especially for other hosts trying to reach it (dynamic DNS? - DNS cache timers?). Security access (ACLs based on static IPs and/or subnet blocks?)
Although L2 migration avoids L3 migration issues, it has scalability issues, both logical and physical. The logical is being addressed by new technologies such as Cisco's OTV and the physical by new "fabric" approaches (often similar concept to what FibreChannel).
