campus design

[penoberger]

Hello all,

I'm relative new in cisco networking and i need some clarifications on cisco hierarchical campus network design.

1. Why do i have to use L3 switches on the core and distribution layers; A router implementing CEF doesn't performs switching in the same speed;

2.In the access-distribution layer(switch block), does 1 vlan has to be restricted in the boundaries of 1 access switch or is it better to extend to more than 1 access switches by using L2 ports on distribution switch? (I think that L3 traffic load balancing on the uplinks to distribution switches - using 2 distrib. switches - is done only if configure 1 vlan per access switch, doesn't it?)

ANY help will be appreciated.

THANKS

Peter

[vladrac-ccna]

I'm not a desing expert, but I work on a network that follows cisco hierarchical designs.

1. the question should then be? Will you be using a layer 2 switch to connect 2 cores and 2 distributions routers (for redundancy and load balancing)?

2. For what Ive seen its better to keep the vlans for just a single access switch to avoid STP issues (and suboptimal layer2 paths).

For the load balancing, you can configure HSRP for vlans configured in more than 1 access switch.

Im not sure I've followed your questions.

But, just my thoughts on the subject.

Vlad

[bhedlund · Accepted solution]

Your statement about CEF is not quite accurate. A Layer3 switch such as a 6500 or 4500 can Layer3 CEF switch as fast as it can Layer2 switch, at wire speed.

In a Routed Campus Design, with Layer3 all the way up to the Access Layer, you can have as many VLANs in the Access Layer as you want because the Access switch will be the Layer3 termination for those VLANs.

I have attached some documents you will find useful.

Please remember to rate all helpful posts.

Regards,

Brad

[penoberger]

Thanks Brad. Your links were extremely helpful.