L2 Network Design Advise.

[leedsit]

Hi,

I have just started to build a simple network with the following kit

2x3560 Swiches IOS Plus
6x3560 Standard IOS

The two IOS Plus 3560 will each have 2 Layer 3 interfaces too two vlans, and those Layer 3 interfaces will be HSRP`s for resilience, each of the 2 switches will have IP Flex to talk back to Head office in an IP Secure Plus Config.

however, my issue, or question is what is the best way to connect all of these 8 switches together??? I`ll have Rapid spanning tree looking after extra links, but there a numerous ways that I can do this, Please see small picture below of the possibilities.... Can I please have your thoughts?

LEEroy
MCNE6,CCNP,CWNA,CCSA,Project+

 

[leedsit]

P.S Ignore A on the diagram above, that situation wont work in a switch outage

LEEroy
MCNE6,CCNP,CWNA,CCSA,Project+

 

[ADB100]

The best way to do this is to connect each Layer-2 switch directly back to each core and don't interlink them. Each access layer-2 switch should have it's own Data VLAN (plus Voice VLAN if you are using voice as well?) that terminates on each Core. The uplinks from the each access layer switch should be configured as trunks but only allowing the 2 VLAN's relevent to the switch. There should also be a layer-3 link between the 2 cores:

This in my opinion is the best way to do this since it eliminates any STP loops and allows core failover to be dictated by HSRP timers.

HTH

Andy

 

[leedsit]

Hi,

Thanks for this.. however I forgot to mention my issue, each 3560 has 4 GIG ports, Hence my issue, If there was 2 L3 Switches and 4 Flat switches then this would be fine, however there are 6 L2 Switches!

What Im thinking is B is the best solution ( has one resilient path ) but channel each fibre giving me 2GIG connectivity.

Lee.

LEEroy
MCNE6,CCNP,CWNA,CCSA,Project+

 

[Jsteve]

I agree with ADB100, that would be the way I would go. You could use the copper ports to make up for the lack of fiber ports. If you only have fiber runs between floors, than you could purchase media convertors, fiber <-> copper.

Lets say you go with the B design and the first L3 swiths is configured as the root. One of the uplinks on the second L3 switch will be blocked, most likely the far right. So the first L2 switch on the right needss to send a packet to the second L3 switch, it will send it down the other l2 switches, up to the STP root, down all three l2 switches on the left and back up to the second L3 switch.

i believe with that design you would have sub-optimal packet forwarding and latency problems.

with ADB100 design the packets will never travel 2 switches away.

 

[ADB100]

You would be better using Cisco Catalyst 3750G-12S in the core. This switch has 12 SFP ports that could accomodate the design I gave you.

Andy

 

[leedsit]

Hi,

Thanks for your input guys, I have designed networks before with the above suggestion, issue is I have been asked to get this working with 8 Spare 3560`s. Hence querying the best way to move forward.

Taking into consideration your advise, I think the design below is the best compromise... also bearing in mind the fibre trunks will be trunking 2x vlans, so I will use 802.1w but blocking vlan 1 on 1 Trunk and vlan 2 on another trunk to load share the traffic.

LEEroy
MCNE6,CCNP,CWNA,CCSA,Project+