route or switch on the core Layer

[saciidxuseen]

                   I am working on a new network design for my company with four buildings, I have used building distribution method for all buildings, my design seems to be functioning properly, I have configured vlans and eigrp routing on the distribution switches as you can see on the diagram, but used the four core layer switches just for switching not routing and I did not configure any routing on them, I would like to know if this is good design or do I need to configure routing on the Core Layer as well

[Jon Marshall]

There is no right or wrong answer to this. Originally the recommendation was to switch in the core ie. use only L2 because L2 switching as fast and L3 routing was slow.  But then L3 switches appreared and the recommendation was to use L3 to connect to the core.

But both are just recommendations. You don't have to follow the guidelines slavishly.

Having said that, looking at your design there are a lot of redundant paths between switches. This means lots of loops and using L2 will mean blocked paths in the core and potentially blocked paths to and from the core. If you used L3 connections from the distrbution to the core and between the cores you would be able to utilise all the links and hence get more bandwidth.

In addition if a link failed you would not be reliant on STP to bring up a redundant path as all paths would be in use (although you should still run STP).

Couple of other points -

1) you have 4 switches in the core - what is the reasoning behind this ? is it distance limitations between buildings ?

2) your addressing. Ideally you would want to be able to summarise from one building to the other so it would make more sense to have all the 192.168.x.x networks in one building and all the 10.x.x.x networks in the other. Actually it would make more sense to decide on an IP range ie. 10.x.x.x or 192.168.x.x (not both) and then use summarised ranges for each building.

Jon

[saciidxuseen]

I must thank you Jon, you absolutely cleared my confusion, for the 4 core switches I have them on the same building but could not put them on the same place, other networks like WAN, enterprise edge and internet are on two different floors on which I put 2 core switches each.

I am doing the remaining bits of the design and may post some other questions if I need to.

Thanks again

[Joseph W. Doherty]

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As Jon noted, L3 cores are the more modern approach with the advent of fast L3 switches.  A L3 core might offer some advantages over a L2 core.  First, often they have faster convergence, L3 vs. STP timing.  Second, might have faster link L3 outage detection (p2p vs. multilink VLAN).  Third, they might deal better with multicast between routers (although Cisco does have PIM snooping).  Lastly, they might have better link usage (no STP blocked paths and multiple path).