STACK RING

[sivam siva]

Hi

Im just learning stack wise technology ,I'hv a doubt in that

while connecting LAN cables in ring type loop will happen, to prevent that STP comes into picture.

likewise while connecting stack cables in ring type why loop is not happening ?

Hope you understand my doubt,help me anyone please.

Thanks in Advance

[marce1000]

 - Stacking connections and protocols are no LAN connections, they bare no relation to the subject of network loops.

M.

[mkazam001]

the stack rings are used for the backplane so they do not create loops

you can stack up to 9 switches together if 3750s as an example - they will appear as a single logical switch with a single mgmt IP address

see below for example command that shows the speed

Switch# show switch stack-ring speed

Stack Ring Speed        : 32G
Stack Ring Configuration: Full
Stack Ring Protocol     : StackWisePlus

regards, mk

please rate if helpful :)

[Joseph W. Doherty · Accepted solution]

Physically, they do create a loop. The reason why STP isn't needed with StackWise it uses a proprietary protocol to deal with the loop. BTW, you'll see similar (i.e. no STP) on other equipment (both Cisco and non-Cisco) that makes physical loops. For example VSS for another proprietary solution, or link aggregation (both proprietary and non-proprietary), or something like REP, etc.

[sivam siva]

Thanks for your reply 

can you tell me how satckwise and stackwise+ protocols eliminate the loops ?

@mkazam001 told that its acting as a back plane,i can understand that, but im little bit hard to conclude 

[Joseph W. Doherty]

Not really, as they are proprietary. In fact, until StackWisePlus, some of StackWise features weren't described until Cisco highlighted StackWisePlus's improvements. For example, unicast traffic on StackWise is taken off the ring once it goes all away around back to the sending switch, where as StackWisePlus's destination switch removes it off the ring. Also, every StackWise connected switch places all its traffic on the StackWise ring, even trafffic to another port on the receiving switch. StackWisePlus, though, only places unicast traffic on a StackWise ring when it's destination is to another switch. (Besides the doubling of bandwidith for StackWisePlus, the two aforementioned improvements might make a huge difference for StackWise bandwidth consumption. [This is why, I recommend not mixing the StackWise and StackWisePlus switches in the same stack, as you lose these benefits.])

[sivam siva]

thank you very much

can you tell me this also,

does stackwise technology differs for every switch models ?

[Joseph W. Doherty]

Yes and no. The main difference, based on hardware, is StackWise vs. StackWisePlus, the latter arriving with the "E" series (and also the later "X") series.
The running IOS version impacts the version and release of the StackWise(Plus) software. So, even with the same models in a stack, you can run into issues if the StackWise(Plus) software differs between individual switches. (Which is why it's suggested you always run the same IOS version/release on all the switches in the same stack, although I recall they should work if the StackWise[Plus] software is the same version.)

[sivam siva]

Thanks for your helpful information @Joseph W. Doherty