Campus Design Problem - Redundancy, HSRP, STP, VLANs...

Discussion in 'Cisco' started by toddedu@yahoo.com, Sep 17, 2007.

  1. Guest

    Access1 (Servers, Internet)
    / \
    / \
    L2trunk_A / \ L2trunk_D
    / \
    / \
    / \
    / \

    Dist1-----------------Dist2 (L2trunk)
    \ /
    \ /
    \ /
    L2trunk_B \ / L2trunk_C
    \ /
    \ /
    \ /
    Access2 (Clients)
    /
    / L2 trunk
    /
    AP1

    THE PROBLEM:

    The way we are planning to be setup - add Dist2 and run HSRP for both
    Vlan1 and Vlan2.
    Dist1 will have higher priority in both HSRP and STP for VLAN1. Dist2,
    higher priority for HSRP and STP for VLAN2. Both Dist1 and Dist2
    perform InterVlan Routing.

    All servers and Internet devices are on Vlan1 (currently flat
    network).

    Looking at the traffic pattern (client to server) according to this
    plan, a client on VLAN2 wired to Access2, will hit Dist2 cross Vlans
    to Vlan 1, then cross to Dist1 (since L2trunk_D will be effectively
    blocked by STP for VLAN1) and using L2trunk_A will get to the server.

    The return path: From the Server wired to Access1, through L2trunk_A
    to Dist1, cross VLANs to VLAN2 (L2trunk_B blocked for VLAN2), get to
    Dist2 and down to Access2.

    Obviosly not the most efficient way to switch/route traffic.

    The HA Campus Design paper on Cisco's web site doesn't seem applicable
    here, because of the Access Points (spread all over campus) running
    multiple SSIDs on multiple VLANs, hence L2 trunking needed!

    I'd appreciate any input from you!
     
    , Sep 17, 2007
    #1
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  2. Merv Guest

    I would route between access switches and distribution and lose STP
    whereever possible. While most AP are bridges that does not mean that
    they cannot land on switch port that is routed.

    Layer 2 VLANS spanned across multiple switchs will typically cause one
    thing - a big headache.
     
    Merv, Sep 17, 2007
    #2
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  3. Guest

    On 17 Sep, 21:56, Merv <> wrote:
    > I would route between access switches and distribution and lose STP
    > whereever possible. While most AP are bridges that does not mean that
    > they cannot land on switch port that is routed.
    >
    > Layer 2 VLANS spanned across multiple switchs will typically cause one
    > thing - a big headache.


    One headache you might have is unknown unicast flooding.
    http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00801d0808.shtml

    The moden way seems to be to have no L2 infrastructure links at all.

    http://www.cisco.com/en/US/netsol/ns656/networking_solutions_design_guidances_list.html
     
    , Sep 18, 2007
    #3
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