DCII: Configuring Port Channels

Port Channel Overview:
• bundle multiple physical links into a single logical link ➡️ improves resiliency and optimizes bandwidth utilization
• between two devices
• point-to-point
• port channel, port aggregation, and EtherChannel (Cisco brand name) refer to the same

Port Channels and LACP:
• passive: does not initiate LACP negotiation, responds to LACP packets
• active: sends LACP packets, initiates negotiation
• all member ports must have the same type of configuration (speed, duplex, access/trunk, [allowed] VLAN, etc.)

Port Channel Mode Options:
• passive + passive = ❌
• passive + active = ✅
• active + active = ✅
• on + [active | passive] = ❌
• on + on = ✅

Port Channel Load Balancing:
•distribute packets across the physical links by hashing various header fields
•calculate based on source/destination L2 MAC addresses, L3 IP addresses, or L4 ports
•choose the most granular option
•does not guarantee equal distribution
•cannot control the port that a particular flow uses ➡️ only influence the load balancing with a frame distribution method that results in the greatest variety
•perfect load balancing possible only with 2, 4, or 8 ports in the channel
•more: Understanding EtherChannel Load Balancing and Redundancy on Catalyst Switches

vPC Overview:
• two upstream switches act as a single logical device
• loop-free topology (both uplinks active/no STP blocked ports)
• downstream device can be any LACP-capable device
• fast convergence if either link or device fails
• two active control planes

vPC Guidelines:
•switch types: must be the same platform
•link speed: 10/40/100 Gbps
•vPC peer and keepalive: use separate links
•vPC domain: one per switch or VDC; two vPC peers
•vPC member ports: must be on same line cards
•routing: dynamic ❌, static with FHRP ✅

Setting up vPC:
•enable the vPC feature on the vPC peers (N7Ks)
•define vPC domain
•configure vPC peer keepalive link (recommended: use separate VRF)
•configure vPC peer link
•configure vPC on the vPC peers
•configure regular port channel on the downstream device