How to Implement a layer 3 switch backbone ring?

[pramod431]

Can anybody explain how to implement a backbone ring with layer 3 switches and each layer 3 switch has its own lan. Please find the attached drawing for a rough idea.

Is it better to assign ip address for l3 switch ports in the ring and use a Layer 3 protocol for routing or use a ethernet STP?

Thank you,

Pramod.

[Joseph W. Doherty]

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The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

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Posting

It's probably "better" to route between the devices as data should normally take the shortest physical path between devices.  With STP, worst case, a pair of devices physically adjacent might need to send their frames across all the other switches.

[Giuseppe Larosa]

Hello Pramod,

as already suggested you can use routed ports between the L3 switches and a routing protocol like OSPF or EIGRP over them.

interface type x/y

no switchport

ip address x.x.x.1 255.255.255.252

You can use /30 IP subnets on each single L3 link.

This also provides for limiting the size of STP domain and each site will have its own STP domain.

Hope to help

Giuseppe

[pramod431]

Hi Joseph & Larosa,

Thanks for the replies, I just have one more question, for example, lan subnets of the L3 switches are 10.1.1.0/24, 10.1.2.0/24, 10.1.3.0/24 and so on. each lan device has a gateway Ip address which is the vlan ip address of the corresponding L3 switch.

In this situation is there any other way other than using L3 protocols we can implement the ring?

Thank you,

Pramod.

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

As you already have different subnets per devices, could your clarify your reluctance to use p2p L3? 

You can share a transit subnet between all the L3 switches.  Each L3 switch would see all the others as logical peers.  "Ordinary" STP could maintain ring redundancy, or if the devices support it, you might use REP.

[pramod431]

Thanks again, as far as I know p2p L3 is better, I was just trying to know whether there is another better way than p2p L3. With your answers now I am confident that L3 routing is more suitable to this type of network.

Thank you,

Pramod.