LAN topology & star or circle.

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Apr 8th, 2009
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Hi all,

Id like to discuss topology of LAN.

Presently we have circle topology and we want to change it to star with one central

hub switch and other access (spoke) switches.

My question is if Cisco WS-C3560G-24TS-E, or WS-C3750G-24T-E as hub switch is enough for 12 access switches?



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Leo Laohoo Thu, 04/09/2009 - 02:14
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WS-C3750-12-E is what you'd be looking for. If you want, there's also Metro Ethernet versions where you can mix Gig with 10Gig.

Joseph W. Doherty Thu, 04/09/2009 - 03:58
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If you links between the hub and spoke will be copper gig, either will likely be fine.

The 3750 will be more expensive, since you can stack it with other 3750s.

You might not need the -E versions, the -S might do you and it's also less expensive. (You can also purchase an upgrade to -E later [the difference is the software], if necessary.) This is assuming you're only going to route on the hub device (if you were planning to just do L2, you could use a L2 switch as your hub, e.g. 2960G).

If you move from a loop topology to a star topology, you might lose fault tolerance. For example, if your single hub fails, you lose connectivity between access switches. This situation can be dealt with by using dual hubs, either standalone or stacked 3750s.

andrew.butterworth Thu, 04/09/2009 - 05:49
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Neither should really be a design recommendation. For a highly resilient network of this size you should consider a collapsed core with either two separate core switches or a stack of two 3750's as the core. You should also really use two uplinks from each access-layer switch to the core in case of a failure.

Having a single core switch presents a huge single point-of-failure and will simply wipe out your network. Having a dual-core or stack with redundant uplinks ensures the network will continue should a failure occur in the core.

Have a read of the Campus design guidelines at the SRND site:



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