Routing versus STP (CCDA)

darkerosxx · July 2008

I'm reading that it's better to implement multi-layer switches and use routing to take advantage of load-balancing instead of using L2 switches and STP. While I can accept that it's better and more efficient, I'm not familiar with how the routing effectively replaces the STP function in L2?

Can anybody help explain this to me?

liquid6 · July 2008

I think the main thing is failover/load balancing, you can use routing to decide if a link fails to use another link instead of waiting for STP to reconverge. Now with RSTP the gains are possibly minimal in time, but for a campus design you can remove L2 from the distribution/core and leave it at the access layer.

Just another way to think about it really.

liquid

darkerosxx · July 2008

Nevermind, I'm retarded! lol i wasn't even thinking about STP being only needed in a L2 switched environment...

darkerosxx · July 2008

liquid6 wrote:

I think the main thing is failover/load balancing, you can use routing to decide if a link fails to use another link instead of waiting for STP to reconverge. Now with RSTP the gains are possibly minimal in time, but for a campus design you can remove L2 from the distribution/core and leave it at the access layer.

Just another way to think about it really.

liquid

Yeah, that's what the book is saying. Thanks for the help, liquid.

darkerosxx · July 2008

liquid6 wrote:

but for a campus design you can remove L2 from the distribution/core and leave it at the access layer.

Just another way to think about it really.

liquid

Diane Teare Book wrote:

Even if the recommended design does not depend on STP to resolve link or node failure events, use STP in Layer 2 designs to protect against user-side loops. A loop can be introduced on the user-facing access layer ports in many ways, such as wiring mistakes, misconfigured end stations, or malicious users. STP is required to ensure a loop-free topology and to protect the rest of the network from problems created in the access layer.

Good idea for those offices where people like to plug up extra switches all over the place.

malcybood · July 2008

darkerosxx wrote:

Good idea for those offices where people like to plug up extra switches all over the place.

Been there.....

Spanning tree was disabled without our knowledge when we created a voice VLAN on our head office access switches. bug in the switch software that disabled STP when a certain command was executed! User plugged the data cable from a hot desk IP phone into a live wall point which caused the L2 loop.

It brought a floor of 150 users to a halt until we resolved!

It wasn't a Cisco switch but still took a while to narrow down the cause as STP was enabled as far as we were aware!

Routing versus STP (CCDA)

Comments