Link between distribution switches

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Oct 2nd, 2008
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Hi all, Can anyone tell me, why we need the link in between my distribution layer switches? is it so that we can use things like hsrp, and also if a link goes down from one of the access switches to the dist layer, it can travel using the link between the dist switches and use the other dist switch to get there?

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Giuseppe Larosa Thu, 10/02/2008 - 01:18
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Hello Carl,

from the point of view of the single access layer switch in any VLan

D1 --------- D2

| |

|__ Ax_______|

STP will put one link in blocking.

let's suppose D1 is the root bridge.

Ax-D2 link will be blocking.

If the link D1-Ax fails Ax must be reached via the D1-D2 link.

via the D1-D2 link the root bridge is elected for each vlan.

all the links will be L2 trunks.

Your understanding is correct

Hope to help


abdel.ibrahim Thu, 10/02/2008 - 02:07
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The link between the distribution switches is for redundancy..hsrp and all.For access layer redudancy you have to dual home the setup. one uplink to dist(a), and a second uplink to dist(B).

PS: you have to know your STP for this.

babatunde_sanda Thu, 10/02/2008 - 03:42
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You are right. It is basically for redundancy. And you can even configure ether-channel on the links between them for faster packet transmission. So instead of either being aware the other is down through the access layer switches it will know faster through the links between them. Another good reason will be faster routing protocol convergence assuming you are running any i.e EIGRP. Basically its all about redundancy which makes your life easier as an engineer.

Hope this helps.


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