core dist and access

carl_townshend · ‎01-22-2008

Hi all, can anyone give me a typical set scenario for this to help me understand, ie would be have routers or switches in the core, why would we need the core if our layer 3 switches in the dist layer can do all the routing/redundancy etc ?

shrikar.dange · ‎01-22-2008

hi,

The access layer provides user access to network devices.Generally it is layer 2 switches and connects the LAN devices such as servers and desks.

The distribution layer uses the L2 & L3 swiching to implement security restrict bandwidth and isolate n/w problems.This provides core layer the neccessary protection.

The core consists of high speed backbone (as fast as possible).Because the core is critical for connectivity and adapts quickly to routing and topology changes.

HTH,

regards,

shri :)

ohassairi · ‎01-22-2008

we can mix distribution and core layers in one layer. this is called collapsed backbone.

but think about a campus, you have many huge buildings. each building with many floor.

for each building you can have a network with access and distribution layers.

now how will you link all these buildings. you need the core layer to connect them.

carl_townshend · ‎01-23-2008

what will the core layer consist of, layer 3 switches, or routers ? and do people normally use layer 3 in the core to avoid spanning tree ?

ohassairi · ‎01-24-2008

core will not perform any intelligent function like acl,... because it must be as fast as possible.

so layer 2 switches will be the most fast because they switch based on layer 2. but il should be a high end switch with 1G or 10G ports et great performance. so at the end it will be 6500 or 7600 switch.

carl_townshend · ‎01-25-2008

I was told to use layer 3 in the core ? is this right, ie use layer 3 switches and route the traffic ?

ohassairi · ‎01-25-2008

if we consider the campus senario, then every building will have a subnet. so you need routing and so L3 switches.