Link public IP, ISP name, and link type auto discovery

Products

• VMware VeloCloud SD-WAN

Issue/Introduction

In cases where auto detect overlay is used. the edge automatically discovers the link public IP, ISP name and link type.

In this article, we will discuss in details how this happens.

Cause

 

• When the edge starts building tunnel with a VCG or another edge, the edge sends an init packet to the peer. The packet exits the edge with the interface IP as source IP but may get natted on the next hop.
• When the peer receives the init packet, it adds the source IP of the packet in the VCMP header INIT ACK and sends it to the initiator edge.
• The initiator edge uses the field "myPIP" from the INIT_ACK packet as the link public IP.
• The process happens again with every new tunnel establishment with any peer.
• The edge always keep using the last discovery until a new one happens when a new tunnel is established. This includes dynamic tunnels also.

 

• The ISP name is discovered  by the VCO using the public IP through Maxmind. The VCO will use the public IP as the ISP name if it failed to resolve the ISP name.
• The link type is set according to the public IP discovered, if the IP is matching the RFC1918 private IPs then the link type will be set to private, it the public IP is out the RFC1918 ranges then the link will be set to public.
• All GE/SFP interfaces will be set to wired by default and all USB/CELL interfaces will be set to Wireless.

Resolution

•  The public IP shown is the link IP as seen by other edges/VCG.

               In many cases, the IP on the edge interface is natted on another device before the packet is sent to other edges/VCGs so we learn this IP                   dynamically.

• The ISP name is discovered by the VCO using the public IP through Maxmind

Additional Information

The Link type can be modified manually if the overlay was changed to "User defined" but the public IP is always dynamically discovered.