Re: Measuring VLAN performance

Discussion in 'Cisco' started by Trendkill, Jun 8, 2009.

  1. Trendkill

    Trendkill Guest

    On Jun 8, 7:17 am, "Gerard Gallagher" <> wrote:
    > Hi all,
    > I'm in the process of converting a flat network (approx 2000 users) to a
    > more layered approach using VLANS.
    > We have 2x Cisco 6509 switches with Sup720's configured as a HSRP core,
    > linked with a l3 etherchannel, and an l2 etherchannel.
    > Each closet will comprise 3 vlans - one for voice, one for data and VLAN1
    > for management.
    > I would like to know how the addition of vlans is affecting the overall
    > network - i.e as areas come off vlan1 for user traffic and get moved to
    > their respective vlan how the overall network performance is hopefully
    > improving, and I'm looking for any information that would help me measure
    > this, or indeed any aspect of the network which I should be measuring. The
    > idea is to be able to show how the vlan introduction is helping the site.
    > Many thanks in advance.
    > Regards,
    > Ger

    To be honest, you shouldn't see much benefit or disadvantage to the
    change in architecture. Presuming your old config was a single vlan,
    the only traffic that will be greatly reduced is broadcast
    traffic...but for 2000 nodes.....not a big deal on a gig or multi-gig
    network. In the old config, nodes off closet 1 would broadcast for
    any of the other 2000 nodes, but the traffic itself would only go
    between source and destination (within the closet or to another
    closet, etc). Now the nodes will only arp within the same closet,
    greatly reducing broadcasts across the core. To be honest, all you
    are doing is enabling the routing on the 6500s which will now control
    traffic between vlans, when before, they probably only controlled
    ingress/egress to the single vlan. So you are definitely doing the
    right thing in terms of scalability, but I doubt you will see any
    major performance increase...unless you had slower links or some major
    load that would drive broadcasts...but arp/cam timers should limit
    that impact.
    Trendkill, Jun 8, 2009
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