Sunday, December 31, 2017

Cisco CCNP:300-115 - 1.5 Configure and verify EtherChannels: 1.5.a LACP, PAgP, manual

Recently I needed to renew my Cisco CCNPs, that is both CCNP Routing and Switching as well as CCNP Security. While working with Cisco products (well now they own SourceFire, so exclude these) is not within my daily duties, I still thought it was important for me to maintain these two credentials. As a result, I've put together my notes below focusing on the key points I used to study. I believe that someone else may find them useful.


        - Provides fault-tolerant high-speed links between switches, routers, etc
        - If a link fails, traffic is redristubted to the remaining interfaces
        - Provides up to 800 MB/s on Fast EtherChannel or 8 Gb/s (Gigabit EtherChannel)
        - All ports must be either L2 or L3
        - Up to 48 Etherchannels
        - can be configured as PAgP, LACP or ON
        - Both ends of the channel must use the same protocol to participate in the channel
        - EtherChannel mode "on" means no negotiation but both sides must be configured for "on"
        - Changes made to the port-channel interface is applied to all physical ports applied to the port-channel
        - Configuration changes made to the physical port, only affects the port where the change was made
       
       
      - Port Aggregation Protocol (PAgP)
          - Cisco proprietary
          - Can only run on Cisco devices or devices licensed by vendors
          - Facilitates automatic creation of EtherChannel
          - Similarly configured ports are grouped based on hardware, administrative, port parameter, etc. Basically similar speed, duplex, native VLAN, etc.
          - The EtherChannel bundle is added to the spanning tree as a single switch port
         
          PAgP Modes
            - auto: This is a passive state in which the port only responds to PAgP packets but does not start PAgP negotiation
               
            - desirable: this is an active negotiating state, in which the port actively tries to negotiate the channel
           
            - Both "auto" and "desirable" allows for negotiation with partners to form an EtherChannel
            - Ports can form EtherChannel even if they have different modes as long as the modes are compatabile.
            - "desirable" and "auto" can negotiate a channel
            - "desirable" and "desirable" can negotiate a channel
           
         -  Cisco CDP and DTP send and receive packets over the physical ports in the EtherChannel
         -  Trunk ports send and receive PAgP protocol data units (PDUs) on the lowest number VLAN
         -  In Layer 2 EtherChanne, the first port to come up provides the MAC address for the channel
         -  If the port is removed from the bundle, one of the remaining ports in the bundle provides its MAC address for the EtherChannel
         -  PAgP sends and receive messages only on ports that are up and enabled for "auto" or "desirable"
        
           
      Link Aggregation Control Protocol (LACP)     
        -  LACP defined as IEEE 802.3ad
        - Facilitates creation of EtherChannels between switches which support LACP
        - Groups similarly configured ports into single link
        - LACP adds the grouped ports to spanning tree as a single switch port
        - LACP operates in two modes:
          - active: Port is placed in "active" negotiating states
             
          - passive: Port responds to receives packets but does not start negotiation
       
        Ports can form EtherChannel once they are in compatible modes
        - "active" and "active" can establish a tunnel
        - "active" and "passive" can establish a tunnel
        - "passive" and "passive" cannot establish a tunnel

        -  Cisco CDP and DTP send and receive packets over the physical ports in the EtherChannel
         -  Trunk ports send and receive LACP protocol data units (PDUs) on the lowest number VLAN
         -  In Layer 2 EtherChannel, the first port to come up provides the MAC address for the channel
         -  If the port is removed from the bundle, one of the remaining ports in the bundle provides its MAC address for the EtherChannel
         -  PAgP sends and receive messages only on ports that are up and enabled for "auto" or "desirable"
        
      - EtherChannel "on" mode
          - Used to manually configure trunks linke
          - No negotiations mechanism (PAgP or LACP) used
          - Both ends of the switches must be configured as "on"
          - All ports must have compatible characteristics
       
       -  Improperly configured EtherChannel ports are automatically disabled to avoid network loops and other problems
      
       -  Configuration tips
          - No more than 48 EtherChannels should be configured
          - PAgP should have no more than 8 Ethernet ports of the same type
          - LACP EtherChannel can have up to 16 ports of the same type. However, only 8 are active while the other 8 are standby-cpu
          - All ports should be at the same speed and duplex
          - A port which is disabled using "shutdown" command is treated as a link failure and traffic is transferred to the other ports
          - The following must be changed on all ports in the group:
              - Spanning-tree path cost for each VLAN
              - Spanning-tree port priority for each VLAN
              - Spanning-tree Port fast setting
             
          - A port should only be a member of 1 channel-group at a time
          - Do not mix EtherChannel modes
          - Do not configure a SPAN destination port as part of an EtherChannel
          - Do not configure a secure port as part of the EtherChannel
          - Do not confiure PVLAN on EtherChannel Port
          - All ports must be in the same VLAN or must be configured as truks
          - Ports with differnt native VLANs cannot form an EtherChannel
          - All ports must use the same trunking protocol (ISL or IEEE 802.1Q)
          - Allow range of VLANs must be the same
          - Ports with different spaning-tree port can can for EtherChannel


References:
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3560/software/release/12-2_52_se/configuration/guide/3560scg/swethchl.html#wpxref12539

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