Tag: lacp

Link Aggregation (LAG) Port (EtherChannel – Cisco)

by Samuel Mitchell, posted in Cisco, Routing & Switching

In the field of networking, there is a concept called Link Aggregation (LAG) which is a technology of combining more than one physical link together to make one logical link. This technology is usually implemented to support link redundancy and in some case higher throughput depending on the vendor. This technology is used mostly to connect servers to switches with multiple network cards. LAG ports are mostly connected in pairs of 2 e.g. 4, 8.

in this article, we are going to focus on the vendor Cisco who calls this technology by a different name, “Etherchannel”.

There are two protocols used on the Cisco switches to support Etherchannel:

  • LACP – Link Aggregation Control Protocol (Cisco proprietary)
  • PAgP – Port Aggregation Protocol (IEEE standard)

LACP protocol

  • Active
  • Passive

PAgP protocol

  • Auto
  • Desirable

Manual – On

Etherchannel configuration

switch(config-if-range)# channel-protocol [lacp/pagp]

switch(config-if-range)# channel-group # mode [protocol]

Etherchannel load-balance

  • src-mac (default)
  • dst-mac
  • src-ip
  • dst-ip
  • src-dst-mac
  • src-dst-ip

Loadbalance configuration

switch(config)# port-channel loadbalance [balance-option]

Layer 3 Etherchannel

an Etherchannel port become layer 3 (routing) port once your disable switchport on the portchannel

switch(config)# interface port-channel 1

switch(config-if)# no switchport

Show summary of the etherchannel

Tips:

  • Configurations applied to the port-channel interface is also applied to all the physical interfaces assigned to the port-channel group.
  • Layer 3 EtherChannel interface is not allowed on LAN based switches.
  • The following ethernet port settings must be the same when configuring the EtherChannel:
    • Speed
    • Duplex
    • native VLAN
    • VLAN range
    • trunking status
    • trunking type
  • When configuring the EtherChannel modes, one side must be in an active negotiating state (Desirable or Active)
  • Maximum interface support in one etherchannel is 8 and the maximum portchannel support on a switch is 64 depending on the switch model.
  • PAgP not supported on cross stack switches.