Switch Topology

Discussion in 'Cisco' started by Gary, Sep 6, 2006.

  1. Gary

    Gary Guest

    We have 2 x 6500 high end switches and several smaller 3500 switches.

    We currently connect the 3500's together using their GIG ports, so have a
    GIG backbone, and each end of the 3500 chain connects into each of the
    6500's

    Would it be better to break the circuit and connect each 3500 to the 6500s
    so a kind of Star topology or make it a fully circular type topology where
    each switch only sees the 6500's through another 3500.

    What is best method here?

    Distances are small in the region of 50ft.

    Gary
     
    Gary, Sep 6, 2006
    #1
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  2. Gary

    Merv Guest

    Gary wrote:
    > We have 2 x 6500 high end switches and several smaller 3500 switches.
    >
    > We currently connect the 3500's together using their GIG ports, so have a
    > GIG backbone, and each end of the 3500 chain connects into each of the
    > 6500's
    >
    > Would it be better to break the circuit and connect each 3500 to the 6500s
    > so a kind of Star topology or make it a fully circular type topology where
    > each switch only sees the 6500's through another 3500.


    YES YES YES !!!

    Why ?

    MUCH easier to trouble shoot

    Lower uplink utilization per 3500 switch as each one would have a
    dedicated link to 6500
     
    Merv, Sep 6, 2006
    #2
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  3. In article <8iHLg.9696$Tl4.6993@dukeread06>, Gary <> wrote:
    >We have 2 x 6500 high end switches and several smaller 3500 switches.


    >We currently connect the 3500's together using their GIG ports, so have a
    >GIG backbone, and each end of the 3500 chain connects into each of the
    >6500's


    >Would it be better to break the circuit and connect each 3500 to the 6500s
    >so a kind of Star topology


    Watch out for oversubscription of the backplane connections
    on the 6500, and make sure that you know which ports of the
    interface card have buffers in common. (Be sure you know
    what kind of fabric connect your supervisor / line-card combination
    is using, and how that fabric bandwidth is divided up between the ports.)
     
    Walter Roberson, Sep 6, 2006
    #3
  4. Gary

    AM Guest

    Merv wrote:
    > Gary wrote:
    >
    >>We have 2 x 6500 high end switches and several smaller 3500 switches.
    >>
    >>We currently connect the 3500's together using their GIG ports, so have a
    >>GIG backbone, and each end of the 3500 chain connects into each of the
    >>6500's
    >>
    >>Would it be better to break the circuit and connect each 3500 to the 6500s
    >>so a kind of Star topology or make it a fully circular type topology where
    >>each switch only sees the 6500's through another 3500.

    >
    >
    > YES YES YES !!!


    I can guess that's the better solution in the world but from the last sentence of Gary (...a fully circular...) I can
    not figure out how the connections could be done.
    If the 3500s are connected in circle and each one is connected to the 6500 how each 3500 can see the 6500 through
    another 3500?

    TIA

    Alex.
     
    AM, Sep 7, 2006
    #4
  5. In article <OqVLg.98127$>, AM <> wrote:

    >I can guess that's the better solution in the world but from the last
    >sentence of Gary (...a fully circular...) I can
    >not figure out how the connections could be done.
    >If the 3500s are connected in circle and each one is connected to the
    >6500 how each 3500 can see the 6500 through
    >another 3500?


    If a link between the 3500 and 6500 were to fail (e.g., cable gets cut
    or GBIC burns out) then the 6500 would still be reachable by sending
    the data to one of the other 3500's connected to the one with the
    link failure.
     
    Walter Roberson, Sep 7, 2006
    #5
  6. Gary

    Gary Guest

    "Walter Roberson" <> wrote in message
    news:deWLg.516277$iF6.2771@pd7tw2no...
    > In article <OqVLg.98127$>, AM <>
    > wrote:
    >
    >>I can guess that's the better solution in the world but from the last
    >>sentence of Gary (...a fully circular...) I can
    >>not figure out how the connections could be done.
    >>If the 3500s are connected in circle and each one is connected to the
    >>6500 how each 3500 can see the 6500 through
    >>another 3500?

    >
    > If a link between the 3500 and 6500 were to fail (e.g., cable gets cut
    > or GBIC burns out) then the 6500 would still be reachable by sending
    > the data to one of the other 3500's connected to the one with the
    > link failure.


    6500 are 3BXL's and from what you are saying I should keep both??

    i.e Connect the 6500's to each 3500 using one of the GBIC ports on the
    3500's and use the other GBIC ports on the 3500s to link them together with
    each other.

    Almost like a chain of 3500's each with a spur to both of the 6500's

    Assuming we have 3 x 3500's and 2 x 6500's we would have 3 x 3500's
    connected in series and each of those 3500's [except the middle one as not
    enough GIG ports] would have a connection to one of the 6500's

    Would it also make sense to mix GB and FE connections so each 3500 turns up
    on both the 6500 switches? Both 6500's switches have multiple upstreams and
    peerings.

    Gary
     
    Gary, Sep 7, 2006
    #6
  7. In article <MHXLg.10017$Tl4.1739@dukeread06>, Gary <> wrote:
    >
    >"Walter Roberson" <> wrote in message
    >news:deWLg.516277$iF6.2771@pd7tw2no...


    >> If a link between the 3500 and 6500 were to fail (e.g., cable gets cut
    >> or GBIC burns out) then the 6500 would still be reachable by sending
    >> the data to one of the other 3500's connected to the one with the
    >> link failure.


    >6500 are 3BXL's and from what you are saying I should keep both??


    >Would it also make sense to mix GB and FE connections so each 3500 turns up
    >on both the 6500 switches? Both 6500's switches have multiple upstreams and
    >peerings.


    Sorry, this is beyond my experience. I would suggest that you look
    through Vincent C. Jones' white papers at networksolutions.com and
    try to find his book on high availability networking.

    More connections sometimes just introduces more ways for things to
    break, so you need a careful plan for high availability with multiple
    peers -- for example, it might involve VRRP (or HSRP). It isn't just
    enough to have alternate topologies available: your setup has to be
    able to reliably detect failures (which do *not* always bring the
    line down), and has to reliably reconfigure around the problem.
     
    Walter Roberson, Sep 7, 2006
    #7
  8. Gary

    Merv Guest

    Dual-homing access switches to dual core ssitches is a standard design
    practice.

    I would eliminate any inter-3500 switch links in favour of using the
    GE's as uplinks to 6500


    6500 #1 ------ 6500 #2
    \ /
    \ /
    3500
    single
    switch
    x n


    BTW can you post a show version from one of the 6500 and one of the
    3500 switches
     
    Merv, Sep 7, 2006
    #8
  9. Gary

    Gary Guest

    "Merv" <> wrote in message
    news:...
    > Dual-homing access switches to dual core ssitches is a standard design
    > practice.
    >
    > I would eliminate any inter-3500 switch links in favour of using the
    > GE's as uplinks to 6500
    >
    >
    > 6500 #1 ------ 6500 #2
    > \ /
    > \ /
    > 3500
    > single
    > switch
    > x n
    >
    >
    > BTW can you post a show version from one of the 6500 and one of the
    > 3500 switches
    >


    Config for inter 3500 links
    simple trunked ports.

    Config for inter 3500 - 6500 links
    6500 end
    interface GigabitEthernet3/18
    switchport
    switchport trunk encapsulation dot1q
    switchport trunk allowed vlan a-d,f,g
    switchport mode trunk
    no ip address

    3500 end
    interface GigabitEthernet0/1
    switchport trunk encapsulation dot1q
    switchport mode trunk
    !


    Why?
    Gary
     
    Gary, Sep 7, 2006
    #9
  10. Gary

    Merv Guest

    Looking for show version from 6500 and 3500 not the trunk configs

    why - because it provide the IOS version you running which translates
    into features that responders may want to suggest that you implement in
    addition to a topology change which I highly recommend you do.
     
    Merv, Sep 7, 2006
    #10
  11. Gary

    Gary Guest

    "Merv" <> wrote in message
    news:...
    > Looking for show version from 6500 and 3500 not the trunk configs
    >
    > why - because it provide the IOS version you running which translates
    > into features that responders may want to suggest that you implement in
    > addition to a topology change which I highly recommend you do.
    >


    3500's are 120.5.1
    6500's are 122.18

    Thanks
    Gary
     
    Gary, Sep 8, 2006
    #11
  12. Gary

    Merv Guest


    > 3500's are 120.5.1
    > 6500's are 122.18



    So it looks like the 6500 are current

    and the 3500 are just about EOL ...
     
    Merv, Sep 8, 2006
    #12
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