Just wondering what does OTV run on? Directly over IP, of UDP or TCP. When I did google search, I see that OTV uses TCP/UDP ports 8472. But the OTV documents say it only adds 42 byte overhead. With 42 bytes, I could not account for TCP or UDP headers in the encapsulation.
Has anyone have full capture of OTV encapsulated packet in Wireshark or something. I wanted to know how OTV is transported over IP network.
The routing protocol used to implement the OTV control plane is IS-IS. It was selected because it is a standard-based protocol, originally designed with the capability of carrying MAC address information in the TLV. In the rest of this document, the control plane protocol will be generically called "OTV protocol".
Thanks for the reply. I have already seen that picture. I need to know if OTV directly over IP, then what is the protocol number (like 1 for ICMP, 6 for TCP, 17 for UDP and so on). Or if it runs over TCP or UDP? I need to know how L2 packets are encapsulated in the Data Plane of OTV.
Thanks again for taking time to answer my question. Much appreciated.
It's actually Ethernet over MPLS over GRE. Here is a screenshot of a wireshark capture of the OTV packet in transit:
The total overhead is 42, like you said. This consists of:
New Outer Ethernet Header – 14 bytes
New Outer IPv4 header – 20 bytes
New GRE Header – 4 bytes
New MPLS Header – 4 bytes
In this particular wireshark capture the OTV edge routers are addresses 126.96.36.199 and 188.8.131.52, which can be seen in the outer IP header. The traffic that is tunneled is between end hosts 172.16.0.2 and 172.16.0.3. Specifically this packet is a 64 byte ping between the two of them.