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NX-OS Port-Channels

posted Mar 24, 2014, 2:59 PM by Rick McGee   [ updated Apr 6, 2014, 8:42 AM ]
Port-Channels
    - Port-Channels EtherChannels, and NIC Teaming terms used to describe the same function
    - Regardless of vendor, 802.3ad (LACP) refers to Port-Channeling 
Used to aggregate bandwidth of multiple physical links between devices
    - E.g. 4 physical 1GE links would form a 4GE logical Port-Channel
Appears as on logic link from STP's protocol 

In a Data Center it's important to make sure that all links are forwarding and not in a blocked state

Port-Channel Load Balancing 
    - Data Flows are load balanced between the member links
        - Single Flow cannot exceed Bandwidth of any physical member link
            a.) E.g. increased lanes on the highway but not the speed limit
            b.) Doen't perform LFI like PPP Multilink 

See this link for more on MLP and LFI
            c.) Still have to do some sort of load balance algorithm 
        - Aggregate of all flows can consume aggregate of PC bandwidth
            -  In the example of 2 10GE links in a port-channel no flow is going to be able to consume more then 10GE at any given time.
        - Going to be load balanced based on L2, L3, and L4 header information 
            - SRC/DST VLAN, MAC, IP and TCP/UDP port
       - Default is SRC/DST for L3 IPv4/IPv6 and SR/DST MAC for non IP
            - This can result in over and under unitized links

Configuring Port-Channels
    - Enable LACP on the switches
        - config t
          feature lacp (global command)
On routers you cannot use LACP so you need to have the Channel mode on (not active or passive)
    - On routers it doesn't matter what port-channel # you assign

When creating or adding member links to the port-channel you want to disable them first before adding them to the port-channel
   

N5K1 
    Conf t
    feature lacp
    
R3
    Routers don't support LACP so no passive or active port-channel mode
    This is one of the reasons why you wouldn't want to run LACP
    you can revert these back to a default configuration with 
    
    config t
    default int gig0/0
    default in gig0/1
    int po1
    ip address 10.0.0.3 255.255.255.0
    int range gig0/0 - 1
    channel-group 1
    no shut


 - On the Nexus platforms because of the number of PC you create with vPC and SAN PC's you want to keep track of what PC number are used
        - You can accomplish this by the " show port-channel usage"

N5K1
    You cannot channel the ports together if they have different configurations.
    conf t
    int e101/1/1 - 2 
    shut 
    channel-group 3 mode on 
    no shut
    int po3
    switchport access vlan 10
    feature interface-vlan
    int vlan 10
    ip address 10.0.0.51/24
    no shut
    
You should be able to ping 10.0.0.3 (router3)
    
Once the port-channels are up run the show port-channel summary 

R2 
    config t
    default int gig0/0
    default in gig0/1
    int po1
    ip address 10.0.0.2 255.255.255.0
    int range gig0/0 - 1
    channel-group 1
    no shut

N5K2
    conf t
    int 102/1/1 - 2
    channel-group 1 mode on    
    int po2
    switchport access vlan 10
    feature interface-vlan
    int vlan 10
    ip address 10.0.0.52/24
    no shut

N7K1-1 
    conf t
    vlan 10
    int e2/1 - 4
    switchport mode trunk
    spanning-tree port type network
    channel-group 1 mode on
    no shutdown

N7K1-2
    conf t
    vlan 10
    int e2/9 - 12
    switchport mode trunk
    spanning-tree port type network 
    channel-group 1 mode on 
    no shutdown

S1 (IP address 10.0.0.10/24) 
N5K1 
    int e101/101/1/4 - 5
    channel-group 10 mode active (running LACP)
    int po10
    switchport access vlan 10

show int e101/1/4 - 5

S3 (IP address 10.0.0.30/24) S4 (IP address 10.0.0.40/24)
N5K2
feature LACP

    int 102/1/6 - 7
    channel-group 30 mode active (running LACP)
    
     
    
    int e102/1/8 - 9
    channel-group 40 mode active

    int po30, po40
    switchport access vlan 10



To test links on servers to see if the flows are evenly distributed use the application Iperf 


When load balancing you want as much information as possible, you would need to change the load balancing method 
    
      N5K's 
     - port-channel load-balance ethernet source-dest-port
      N7K's 
    - port-channel load-balance scr-dst ip-l4port-vlan


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