vPC stands for virtual Port channel or advanced port channel. It is also known as multi chassis port channel.
Traditional port channel can’t bundle the links which are connected to two different
switch.
It was introduced in NXOS version 4.1(4).
It is a layer 2 port channel. There is no concept like Layer 3 vPC.
Speed and Duplex settings must match on all ports.
VPC is a feature being used in Nexus i.e., Datacenter Devices of Cisco 7K and 5K
We will be able to logically combine links of different switches and form Virtual Port channel.
Only two devices can participate in vPC – not more than this.
Steps to create VPC
1) Create VPC Domain (Only one domain can be created in Switch)
2) Create VPC Peer Keep-alive Link (It is a Layer 3 Link)
3) Form VPC Peer-Link (It is a Layer 2 Link)
4) Assign Member Ports
Make sure that VPC Domain number is same on both sides. It should not be changed once VPC is formed else it will cause disruption.
Minimum Port capacity should be 1G for VPC Peer Keep-Alive Link.
Peer Keep-Alive (L3) Link can be formed using port, SVI & L3 Port channels.
Peer Keep-Alive Link can be formed using Mgmt0 Interface as well but not recommended.
Mgmt0 is a single port on Supervisor engine. If you are using Dual Supervisor Engines then a problem will occur when one sup fails.
In that case, you have to manually move the connection of mgmt0 from sup1 to sup2(because it works on the Active Sup only). So, avoid Mgmt0 in this case.
It is always good practice to use dual sup. However, like we discussed above, it is not good to use mgmt0 in this case, instead use normal IP connection or SVI, or L3 port channel.
If you have four VDCs being used in Single chassis, then make sure that Mgmt0 has common subnet being used on all four VDC mgmt0 interfaces.
Though VPC can be formed between VDCs which are part of same Physical Chassis- However, cisco does not recommend and also does not provide support in such scenario.
CISCO FABRIC SERVICES (CFS)
This protocol is used for stateful synchronization and configuration. It utilizes the peer link and does not require any configuration by the administrators.
The Cisco Fabric Services over Ethernet protocol is used to perform compatibility checks in order to validate the compatibility of vPC member ports to form the channel.
To monitor the status of the vPC member ports.
To synchronize the Address Resolution Protocol (ARP) table.
It is also utilize to synchronize the IGMP snooping status.
VPC Peer-Link Goes DOWN
Once Peer-Link goes down then VPC Secondary Switch Suspends the Member ports and stops the VPC operation on VPC Secondary Role Switch.
The “DOWN” Information is passed using Keepalive Link.
There is NO Impact to VPC operation i.e. to Traffic. However, Secondary VPC Switch suspends the operation to Avoid Split-Brain Scenario.
When VPC Peer Keepalive goes DOWN
L3 (keepalive) is down when L2 (peer link) is up, then there is NO IMPACT to operation.
OTV
OTV stands for Overlay Transport Virtualization, used for extending Layer 2 applications over distributed data centers, therefore it is a DCI i.e. Data Center Interconnect.
If you have Vlan 30 in DC1 and Vlan 30 in DC2 separated by Layer3, and then if you apply OTV between DC1-DC2, after that Server of DC1 in Vlan30 will communicate with Server of DC2 in Vlan30 as if they are in same Vlan30 i.e. broadcast domain.
VMs can also be moved from one to another DC in ESX environment.
This DCI can be deployed between sites without changing the existing design & configuration.
OTV is configured on the edge devices and then tunnel is formed so that Layer2 networks can be extended. You can call it Layer2VPN over IPv4/IPv6.
L3 connectivity should exist between DCs.
There are other DCIs as well apart from OTV like DarkFiber, L2TPv3, Atom, VPLS but they have dependencies on one thing or another. OTV just needs IP connectivity between edge devices.
OTV does not allow flooding of Spanning tree to reduce the load in the network.
OTV tunnel does not allow ARP Req/Reply or ICMPv6 Neighbor Discovery messages.
Nexus switch and ASR1000 routers support OTV.
Edge device is the device running OTV.
AED (Authoritative Edge device) – It is an active forwarder for VLAN(s). It uses the concept of Odd/Even for load balancing of VLAN traffic. It helps in loop prevention.
Extend Vlan – the Vlan being extended over OTV tunnel.
Site Vlan – It is the local vlan used for syncing the control plane information of AEDs. It is an internal Vlan used for electing AED.
Site Identifier – It is a unique ID per DC. This ID will be the same on multiple AEDs of a single DC. It helps in loop prevention.
Overlay Interface – It is a logical link or OTV tunnel Interface.
OTV Join Interface – It is an actual physical link or L3 port channel used for routing upstream towards DCI. This cannot be SVI.
OTV uses IS-IS routing protocol for forming trees and neighborship.
Mac addresses in OTV will be advertised unlike in FabricPath. Edge devices have control on what mac addresses will be forwarded over OTV tunnel.
SVI interfaces should not be created on VDC where OTV is configured. So,features like HSRP, VRRP & GLBP will not work on the VDC reserved for OTV.
OTV requires a separate license for functioning.
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