chaining hubs or switches question

ladiesman217

what are the rules when chaining hubs or switches?...I mean the limits of devices that can be connected to facilitate network expansion.

I'm starting to study the CCENT and i need to go through the basics first. Thanks.

techster79

There is no limitation for chaining switches. The limit was with hubs, but I doubt you will be tested on this. It is the 5-4-3 rule:

There can only be a maximum of five segments, connected through four repeaters(hubs), or concentrators, and only three of the five segments may contain user connections, two of the five are unpopulated, and it creates one collision domain.

bighornsheep

techster79 wrote:

There is no limitation for chaining switches.

Only if you're not looping it back anywhere in the campus network or if you're running a newer version of STP, I've never tried this myself, but I've heard from some people that the original STP 802.1D will have problems blocking ports to prevent looping when the loop is beyond 8 hops away, ie. when you chain 9 switches or more together in a loop.

Something to do with BPDU originating from the Root bridge and only being relayed by other switches perhaps?

sir_creamy_

bighornsheep wrote:

Only if you're not looping it back anywhere in the campus network or if you're running a newer version of STP, I've never tried this myself, but I've heard from some people that the original STP 802.1D will have problems blocking ports to prevent looping when the loop is beyond 8 hops away, ie. when you chain 9 switches or more together in a loop.

I've always been told it was 7 hops, although I have no reason why this may or may not be the case.

Interesting article on the implications of this:

http://www.computerworld.com/hardwaretopics/storage/story/0,10801,78803,00.html

APA

Switch diameter should never exceed 7 switches from the root bridge for a 'by the book' topology.

The reason for this is due to the STP timers, STP metrics are tuned for a diameter of 7 switches.