Friday, April 24, 2015

Building a vPC domain

Configuration Steps:-
(Order does Matter !!)

1. Define domains.
2. Establish Peer Keep-alive connectivity.
3. Create Peer Link.
4. Reuse port-channels and Create vPCs.
5. Ensure the configurations are consistent.

vPC Domains:-
vPCs domain ID used to assign unique vPC system MAC address.
vPC Domain IDs should be unique within the layer 2 domain.

Connected hosts/switches to vPC domain see the vPC system MAC instead of the local MAC of the vPC member.

Perr Keep-Alive
Heartbeat between vPC peers.
Active-Active detection (in case vPC Peer-Link is down)
UDP message on port 3200, 96 bytes long (32 byte payload), includes version, time stamp, local & remote IPs and domain IDs.
Default timers: interval 1sec/ timeout 5 sec.

Ensure vPC PKL messages should NOT be routed over the vPC peer link !! (Peer-Link only comes up after we configure the Peer-Keep Alive)
The Peer Keep-Alive is best configured as a dedicated 1/10 GE port. or can be sent along with management traffic on mgmt0. As a last resort, it can be routed over L3 infrastructure.

Peer Link
Standard 802.1q trunk which carries CFS (Cisco Fabric Services) messages.
Carries flooded traffic from vPC peer, STP BPDUs, HSRP Hellos, IGMP updates etc.
Peer-Link must be 10/40/100 GE.
Peer-Link must be point to point link.

Use min 2 x 10GE ports
Use 2 separate cards for resiliency.
10GE ports in dedicated mode for oversubscribed modules.




Differences from STP:-
vPC has an independent Control Plane and Forwarding Plane

For Best Practices
References:- http://www.cisco.com/c/dam/en/us/td/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf 
Quick Config guide:- https://www.cisco.com/c/en/us/products/collateral/switches/nexus-5000-series-switches/configuration_guide_c07-543563.html 

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