What is VPC

--> Virtual Port Channel is a special type of EtherChannel between two switches instead of one.

--> VPC is a part of the multi-chassis EtherChannel family similar to VSS.

--> VPC is cisco technology found in nexus platform.

-->  VPC provides redundancy and dual active paths in the network.

--> As there are two or more paths to two switches, there is no single point of failure. Even one switch fails, traffic still flows.

--> VPC is layer 2 technology.

--> VPC is made of two Nexus switches which form a vpc domain. Each domain uniquely identified by using Domain ID.

--> Each Switch can only be in a single domain. one of the switches will be the primary and other will be the secondary.

--> Both switches forward traffic. The primary switch handles the majority of control plane traffic.

--> VPC switches are connected using two special links.

i) Peer-link ( It is used as backplane between two switches for sending/receiving the control plane as well as sometimes data traffic)

ii) Keep-alive link ( To know another peer is active or not by sending/receiving the heartbeats)

--> Peer-link forwards unicast/multicast/ broadcast traffic between two Nexus switches in vpc domain.

--> Peer-link is used for sharing the MAC table information between two Nexus switches in vpc domain.

--> With VPC, there are two types of ports used in nexus switches.

i) Member Port -- A member port is any port that is configured with VPC, such as ports connected to a server.

--> Any VLANs allowed on the member ports must be allowed on the peer link

ii) Orphan Port

--> An orphan port is any port that has no VPC configuration, such as ports connected to routers.

--> Any VLANs allowed on the orphan ports need not to be allowed on the peer link.

--> VPC uses duplicate frame prevention rule to avoid duplicate frames in the network.

--> Nexus switch in the VPC will drop the frame if it receives on the peer-link and needs to deliver on the member port.

--> If Nexus switch forwards any frame on peer-link and needs to deliver on the orphan port.

--> VPC Pair of switches will appear as one logical switch to other physical switches.

--> By default only the primary switch will send and process BPDU's.