Etherchannel/port-channel


  • Etherchannel/port-channel
  • On different Cisco switches it is possible to create logical connections that
  • are made-up off different fysical interface. It is needed that these interface
  • do have the same speed.
  • Each channel must be made up of min 2, max 8 interfaces.
  • The best is to use 2 ,4 or 8 interfaces. This will give the perfect load-balancing.
  • The load-balancing can be bases on layer 2/3 or 4 information.
  • It is not possible to have different load-balancing methods for different Etherchannels
  • on one switch. If the load-balancing method is change, it is applicable for all.
  • The load-balancing method can be:
  • –          src-mac
  • –          dst-mac
  • –          src-dst-mac
  • –          src-ip
  • –          dst-ip
  • –          src-dst-ip
  • –          src-port
  • –          dst-port
  • –          src-dst-port
  • By using <port-channel load-balance {option}> it is possible to change to method.
  • If a single header is used to load-balance the low-order bits is used to dictate to
  • witch interface the frame is send. If two headers are used a XOR function is used on
  • the low-order bits.
  • It is possible to change what path with-in the etherchannel a frame takes by used the following command:
  • <test etherchannel load-balance interface port-channel [#] ip [src] [dst]>
  • to assign a physical interface towards a port-channel use the following command:
  • channel-group [#] mode on
  • There are two type of dynamic protocols to negotiate an etherchannels: PAgP and LACP 8021.AD
  • PAgP is Cisco proprietary
  • When these protocols start to communicate there is an exchange of information before the port-channel can be formed. The following items must match before a port-channel can form:
  • –          same speed/duplex
  • –          Access VLAN (if not trunked)
  • –          Same trunking type, allowed VLAN and native VLAN (if trunked)
  • –          Each port must have the same STP cost per VLAN with-in the portchannel
  • –          No SPAN ports
  • channel-group [#] mode on (disables PAgP en LACP)
  • channel-group [#] mode off (disables PAgP en LACP and prevent the ports to form a port-channel)
  • channel-group [#] mode auto (use PAgP in a passive mode, it will wait until a PAgP packet will be send)
  • channel-group [#] mode passive (use LACP in a passive mode, it will wait until a PAgP packet will be send)
  • channel-group [#] mode desirable (use PAgP in an active mode, it will start to send  PAgP packets)
  • channel-group [#] mode active (use LACP in an active mode, it will start to send  LACP packets)
  • 3750(config)#interface range gigabitethernet 1/0/2 - 4
  • 3750(config-if-range)#channel-group 1 mode on
  • 3750(config-if-range)#switchport
  • 3750(config-if-range)#switchport trunk encapsulation dot1q
  • 3750(config-if-range)#switchport mode trunk
  • First type the channel-group command. After that all interface commands will be automatically duplicated on all the interfaces group in the channel-group.
  •  
  • With LACP it is possible to create a port-channel on a stack (3560/3750 switches).
  • This is based on IOS version 12.2(25)SEE
  • Show command’s
  • show interfaces port-channel [channel-group-number]
  • show etherchannel [channel-group-number] summary
  • Verify command’s
  • test etherchannel load-balance interface port-channel [#] ip [src] [dst
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About ccie4all
Hello, and welcome to the first post of my CCIE blog This blog has got one simple goal and that is to improve our skills in Cisco Networking field so we can become best engineers on a job market. Wordpress Blog https://ccie4all.wordpress.com/ information about the changes made to Gns3 BGP , MPLS and R&S CCIE labs. In order to access and download all provided materials and receive important updates from Gns3 BGP , MPLS and R&S CCIE labs under GNS3 tab in the main header please go ahead and subscribe to https://ccie4all.wordpress.com/ ! All other posts have not been affected and can be accessed at any given time. Enjoy ! Tom

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