Hi @Yassin Alizadeh Golbazi,
"Provides single-touch site configuration for adding new data centers"
To interconnect a new Data Center to others already interconnected using OTV, you do not have to go to every existing site and add any command in its existing configuration.
Only on the new site you will configure the OTV overlay and related commands.
"Preserves existing Layer 3 failure boundaries"
The OTV provides STP isolation, unknown unicast traffic suppression, and ARP optimization, to stop this traffic from traversing the DCI link (Data Center Interconnect).
- STP isolation - OTV blocks BPDUs over the overlay, thus isolating each site in terms of spanning tree; an STP event in one site will not affect STP in another site. OTV edge devices send and receive BPDUs only on internal interfaces.
- Unknown unicast traffic suppression - Let's say a unicast frame needs to be delivered to MAC aaaa.bbbb.cccc. Because the OTV edge device does not know if a MAC aaaa.bbbb.cccc is present in any other site, it will not send this packet. MAC aaaa.bbbb.cccc might as well be present in one of the data centers, however, OTV assumes that end-hosts are not silent (it will eventually learn about it) or unidirectional (applications that only listen). These assumptions conserve precious bandwidth on the data center interconnect. You can configure exceptions to this rule if required.
- ARP optimization - OTV Edge devices allow first ARP request to be broadcasted to all sites. OTV Edge device then replies to all subsequent ARP requests on the behalf of other devices. In other words, The local OTV edge device answers subsequent ARP requests for the IP address located at the remote Data Center. The result is drastic reduction of ARP traffic over the DCI.
"Provides automated multihoming"
If you have more than one OTV edge device at a site, they will automatically multi-home.
OTV edge devices at the same site exchange hello packets that are based on the fact that they are configured with the same site VLAN and they have the same site-identifier.
OTV will elect an AED on per-VLAN basis. The OTV edge device for a given VLAN will then proceed to advertise MAC addresses and forward traffic. If one of the edge devices fails or loses overlay connectivity, the other will take over forwarding for VLANs of the failed device.
I hope this helps.
Regards.
