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Beginner

Connecting multilayer switches in Core Layer

Hi,

 

I'm working on network project for my Uni. I have to plan a campus network, so I used the cisco 3-Layer hierarchial model and I got stuck in Core Layer.

 

I'm using there multilayer switches (3650s) and I know from this document I should connect together these switches. I don't really know which connection use L2 or L3.

 

I thought about L2 connection and creating Etherchannel for load-balancing but I've been curious how these Core Switches would know to which Distritbution Switch they have to send data. In my distribution layer I used HSRP for redundancy and its working really OK but if I will connect Core Switches with Etherchannel won't they start sending data to each one DistributionSwitch? I want in my DistrLayer one primary switch and one secondary (backup) so I used HSRP.

 

Furthermore I don't get L3 connection between CoreSwitches, what is the purpose of doing it? What will be advantages? 

 

I really appreciate it if someone could help me. I've been studying cisco documents and this forum but I didn't get helpfully answers.

 

 

 

6 REPLIES 6
VIP Mentor

Re: Connecting multilayer switches in Core Layer

Hello,

 

we need to see a layout of your (planned) topology, do you have, or can you provide, a schematic drawing ? Also, are you planning to do the inter-Vlan routing one (one of) the core switch(es) ?

Beginner

Re: Connecting multilayer switches in Core Layer


@Georg Pauwen wrote:

 

are you planning to do the inter-Vlan routing one (one of) the core switch(es) ?

I didn't think about it, I don't think it's necessary here (isn't it?).

 

Here is schema I've been thinking about.

 

 

VIP Mentor

Re: Connecting multilayer switches in Core Layer

Hello,

 

thanks for the schematic drawing. It looks like all your switches have redundant connections to the core switches, so a port channel between the core switches would not really be necessary.

 

I was asking about inter-Vlan routing because you mentioned HSRP. What device (if it is not the core switches) is doing the routing ?

Beginner

Re: Connecting multilayer switches in Core Layer

Thanks for your quick answer,

 

So I'm really a beginner in this network-projecting-stuff and I've read about intervlan routing but I don't get purpose of this in my network. I don't have any vlans here, every switch in access layer is separate subnet. One DistrSwitch is the HSRP active one and second is in standby state  without  vlans, using only subnets. (or maybe I'm doing something wrong)? 

 

I thought core switches can do the routing (that's why is the cloud connected here - that's the ISP).

 

If the connection between core switches isn't necessary can I configure one of them to be in something like 'standby mode'? 

So when distrSwitches have redunant connections to Core we don't have to connect coreSwitches together then why on every cisco's model there is connection? (i.e here ->  http://www.ciscopress.com/articles/article.asp?p=2202410&seqNum=4)

VIP Mentor

Re: Connecting multilayer switches in Core Layer

Hello,

 

-->  I don't have any vlans here, every switch in access layer is separate subnet

 

If each switch is in a different subnet, you need a different VLAN for each switch. Subnet and Vlan in this context are the same thing. It might help to add the actual IP address spaces to the drawing. If you use HSRP (or VRRP, or GLBP), the core switches need to be configured as layer 3 switches and do the inter-Vlan routing.

Beginner

Re: Connecting multilayer switches in Core Layer

Hello, 

-->the core switches need to be configured as layer 3 switches and do the inter-Vlan routing.

 

So I have to configure something like RIP/EIGRP on these switches?

 

What about this interlinking between core switches (that's mine main problem). Can I implement here load-balancing? (or it will be wrong?)

 

If core switches will be connected to ISP can I do something with sending traffic from them to HSRP-standby switch in distribution layer? (I don't want it because that's the backup switch..)

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