CCIE RS – Written – L2 – Implement and Troubleshoot Etherchannel

Implement and Troubleshoot Etherchannel


Etherchannel / Portchannel

Ability to aggregate multiple interfaces into a single logical interface to increase the amount of bandwidth and redundancy when connecting to a node.

Support up to max of 64 etherchannels per switch (4500)

Etherchannel Modes

On – Mode that forces the LAN port to channel unconditionally. In the on mode, a usable EtherChannel exists only when a LAN port group in the on mode is connected to another LAN port group in the on mode. Because ports configured in the on mode do not negotiate, there is no negotiation traffic between the ports. 

Auto – PAgP mode that places a LAN port into a passive negotiating state in which the port responds to PAgP packets it receives but does not initiate PAgP negotiation. 

Desirable – PAgP mode that places a LAN port into an active negotiating state in which the port initiates negotiations with other LAN ports by sending PAgP packets. 

Passive – LACP mode that places a port into a passive negotiating state in which the port responds to LACP packets it receives but does not initiate LACP negotiation. 

Active – LACP mode that places a port into an active negotiating state in which the port initiates negotiations with other ports by sending LACP packets.


LACP

802.3ad

Modes – Active / Passive

  • Open standard
  • Bundle together multiple ports to increase overall bandwidth utilization
    • Acts as a single link
  • Links must have same speed, duplex and type (access / trunk) setting
  • Supports 16 ports in LACP, only 8 can be active
  • Configured in Active / Passive mode
  • LACP parameters
    • System Priority – Forms the system ID and is used during negotiation.
      • Default is 32768
      • Lower value is preferred
    • Port Priority – Used to decide which ports should be put in standby mode when there is a limitation or something preventing a port from aggregating.
    • Administrative Key – Defines the ability of a port to aggregate with other ports.

PAgP

Cisco proprietary

Modes – Auto / Desirable

  • Bundle together multiple ports to increase overall bandwidth utilization
    • Acts as a single link
  • Supports 8 ports in single group, all active
  • Configured in Auto / desirable modes
  • Negotiates with PDU’s, sent and received on lowest numbered VLAN of trunk link
  • Links must have same speed, duplex and type (access / trunk) setting

Manual Etherchannel

Mode – on

For devices that do not support LACP or PAgP


Layer 2

Operates as either a layer 2 access or trunk interface

Layer 3

Assigned an IP address. Can participate in a routing protocol


Load Balancing

To balance the load, EtherChannel uses MAC addresses, IP addresses, or Layer 4 port numbers, and either the message source or message destination, or both

  • src-mac—Source MAC addresses 
  • dst-mac—Destination MAC addresses 
  • src-dst-mac—Source and destination MAC addresses 
  • src-ip—Source IP addresses 
  • dst-ip—Destination IP addresses 
  • src-dst-ip—Source and destination IP addresses (Default) 
  • src-port—Source Layer 4 port 
  • dst-port—Destination Layer 4 port 
  • src-dst-port—Source and destination Layer 4 port
Switch# show etherchannel load-balance
EtherChannel Load-Balancing Configuration:
src-dst-ip
EtherChannel Load-Balancing Addresses Used Per-Protocol:
Non-IP: Source XOR Destination MAC address
IPv4: Source XOR Destination IP address
IPv6: Source XOR Destination IP address
Switch#

Etherchannel Misconfiguration Guard

Protect against misconfiguration on the switch. Recover by shutting and no shutting the interface(s)

spanning-tree etherchannel guard misconfig


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