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TOPIC: designing the core of a switched network

designing the core of a switched network 11 years 11 months ago #20769

I have two core switch/routers (Cisco 4507s running EIGRP). Attached to that are about 4 WAN routers, four L2 4507s, and a dozen small L2 switches. The two core switches have HSRP running for 10 groups. I don't think I have the core configured correctly to prevent HSRP and STP problems.

Should I connect the two core switches with a L2 trunk open to all VLANs? Or should I connect the two core switches with on wire at L3? Should I even physically connect the two core switches at all?


Re: designing the core of a switched network 11 years 11 months ago #20809

  • Dove
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I am not expert on this...but my thoughts on this..(pls correct me if am wrong)

As cisco suggested structured campus network, the core switches should be interconnected with redundent link for failover.


Re: designing the core of a switched network 11 years 11 months ago #20849

  • krik
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As you are talking about HSRP, I would go for a Layer 2 link between the two core switches. I would also configure one of the two core switch as primary root for the spanning-tree and the other one as secondary root so the link between them will always be in STP forwarding state. The Layer two link will avoid to use one of your access switch to switches traffic between your two core.

If you want to load balance the traffic between your two core switches, be careful about the so called "flooding issue" due to asymmetric routing. You can take a look here for more info about that.

Finaly, if you are using a routing protocol, I would configure a dedicated VLAN on the core for this purpose.

Christophe Lemaire
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