Link Aggregation on Cisco SG300

Posted on 2011-10-03
Last Modified: 2012-05-12
I am new to setting up link aggregation and I currently have a Cisco SG300 switch and a Dell 2650 server which has 2 nics that support link aggregation. My switches currently have 3 vlans and I would like to aggregate the two nics on the server so that they can communicate with other devices on the network that are in Vlan 1.  I've made several attempts to get this to work but no success.

First... when I aggregate the server nics, do I have to assign a Vlan to the virtual interface and if so do I set it as tagged or untagged?

Next...on the switch side do I assign my ports as general, access or trunk?
Do I need the assigned ports to the vlan or do I assign the lag to the vlan?  

Thanks for whatever help you can offer.

Question by:phcc75
    LVL 57

    Expert Comment

    Are you going to have more than one VLAN going to the server?

    If more than one VLAN, the switch port must be trunk and the server must tag as needed for each VLAN.

    If only one VLAN, then the switch port can be either trunk or access (I would suggest access).

    If you define the switch port as access, you don't need to tag the VLAN on the server side.  If you setup the switch as trunk, then I would tag the VLAN from the server side.  However, using taged VLAN's when there is only 1 VLAN creates unneeded overhead.

    Author Comment

    OK, here's a bizarre thing I can't figure out.

    I only have 1 vlan of traffic going to the server, so I configure LAG on the SG300 as an access port and I tried untagging the vlan on the server side and I even tried teaming the nics with no vlan config with no success.

    But things got even weirder when I tried some basic ping tests.  Note: The Server is plugged into the Cisco SG300 switch and the SG300 is trunked to a Cisco 24 port 2960, which is trunked to a 48 port 2960.

    This is weird:
     First the server can ping another server that is located on the 48 port switch and vice versa.  Here's the weird part... 2 out of 3 computers (plugged into same switch and are members of the same vlan) can ping the server. However when I reboot the server the computers that were able to ping the server are now unable, while the computer that originally could not ping the server all of sudden can ping it.  This holds true for other devices on the network located on different switches.

    One minute the Server (with nic teaming) can ping all of the switches, then as soon as I reboot it, it looses connectivity with them.

    As soon as I disable one of the NICs in the "Team" everything works as it should.  

    I know this sounds confusing but I can't find any logic to  this.  At first I just thought only devices in the same switch were working while other switches had a vlan issue, but the fact that random computers in the other switches see the Aggregate link and other do not ....just baffles me.  To repeat, all of those computers are in the SAME VLAN!
    LVL 57

    Expert Comment

    How are you setting up the NIC team on the server?  Active/Active or Active/Standby?

    It almost sounds as if you are doing Active/Standby and that at reboot the teaming driver is changing which NIC is active.  This will cause the responding MAC to be different and it may not respond on the now "inactive" NIC.

    Next time you try your test, on the computer that you are ping'ing from try clearing the arp table entry for the computer you are trying to ping.

    Author Comment

    I am so frustratred.  I am using the Broadcom Advanced Control Suite 3 to setup the Nic Team.  I select the 802.3ad option (I am assuming this is Active/Active...right?)   Although, I am somewhat concerned b/c after I setup the Team, one of the nic cards in the teams shows that BASP is active and the other nic in the team say BASP inactive.  So, I am somewhat confused.  

    Accepted Solution

    I finally figured it out!!!   I got a hint as to what was wrong by reading this thread

    The Broadcom Advanced  Control Suite gives three options for NIC TEAMING      
            • Smart Load Balancing
          • 802.3ad Link Aggregation using LACP
          • FEC/GEC Generic Trunking

    The whole time I was trying to use the Link Aggregation using LACP option and I didn't have LACP enabled on the switch side!!!!   As soon as I tried the Generic Trunking option, everything worked!!!!!

    Author Closing Comment

    I thought the 802.3ad NIC team option was the only option to use in link aggregation.

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