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EtherChannel

 

EtherChannel Overview:

  • EtherChannel groups multiple trunk, access, tunnel, or routed ports into one logical port.
  • Configuration settings are placed in the port-channel interface.
  • Layer 2 vs. Layer 3: Member interfaces need to be in the correct layer before being associated with a port-channel.

Useful Commands:

  • show lacp neighbor
  • show etherchannel summary
  • show lacp sys-id
  • clear lacp counters to reset LACP counters.

PAgP (Port Aggregation Protocol):

  • PAgP silent mode: Operates even with non-PAgP devices.
  • Non-silent mode: Faster connection with PAgP-compliant switches.

MLAG (Multi-Chassis Link Aggregation Protocol):

  • Synchronization happens between switches over the control plane.
  • On VSS (Virtual Switching System), control plane is synchronized over Virtual Switch Link (VSL), typically 2x10G LAG.

vPC (Virtual PortChannel):

  • Available on Nexus Series switches.
  • Control plane synchronized over the vPC Peer Link (2x10G LAG).
  • Two independent control planes and two independent management planes.

EtherChannel On Mode:

  • Used to manually configure an EtherChannel without negotiation.
  • Ports in on mode must have compatible characteristics (speed, duplex).

LACP (Link Aggregation Control Protocol):

  • LACP fast: LACP packets sent every 1 second, removing links faster if a failure is detected.
  • LACP slow: Default with packets sent every 30 seconds.
  • LACP rate fast command enables fast mode.

Load Balancing in EtherChannel:

  • You configure load-balancing using the port-channel load-balance command.
  • Options include balancing by source/destination IP, MAC, or both.

Minimum & Maximum Number of Member Interfaces:

  • Minimum links: The EtherChannel can be configured to become active only when a certain number of member links are up (port-channel min-links).
  • Maximum links: Ensures a set number of active interfaces based on powers of two, useful for load balancing (lacp max-bundle).

LACP Priorities:

  • System priority: Determines which switch is the master in selecting active links.
  • Interface priority: Used by the master switch to choose active member links.

EtherChannel Misconfiguration Guard:

  • Detects EtherChannel misconfigurations (like mismatched channel parameters or missing EtherChannel on the other device).
  • Places misconfigured interfaces into error-disabled state.
  • Enabled with the command spanning-tree etherchannel guard misconfig.

Switch Polarization:

  • Occurs when a switch selects the same link repeatedly in a multi-link EtherChannel. Load balancing effectiveness depends on the hashing algorithm and having a power-of-two number of links (e.g., 2, 4, 8).

Load-Balancing Methods:

  • Common methods include source and destination IP/MAC addresses.
  • The command show etherchannel port shows load distribution in hex format.
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