RSTP and non managed switches on same network

[John Anvari]

I have a setup where RSTP is tuned on all HP switches. But I have a few places on the network where a few drops were needed so a netgear five port switch was used to provide the extra connections needed in a classroom. What if any bad effects would this have on the network?

[Allan Bowman · Accepted solution]

As long as the 5-port switches are end points and are not interconnected with each other (or back to another HP switch port), you should be okay. You shouldn't have multiple paths for getting to any of these switches, so RSTP would not come into play.

Allan in Atlanta

** points are always welcome **

[Bruce Campbell_3]

A hub or unmanaged switch will forward
the spanning tree BPDU's unchanged, and
not interact with spanning tree in any
way.

An occasional situation at our site is that
a user will have a hub or unmanaged switch
in their office, and then they connect
it to *both* wall jacks (to make it
go faster I guess).

spanning tree on the upstream switch sees
the BPDUs sent to one wall jack
returning on the other, and it blocks
one port, having detected a loop.

[John Anvari]

Great. Thanks. Another question. I am a little new to this. I have RSTP on for two reasons. I am in a school system and the kiddies often would loop the network on purpose. Problem solved. I used RSTP because DHCP would time out if STP was used. I have Cisco in the mix also but I cannot use thier stp due to DHCP issues. So until I get rid of them. Can I also have RSTP on with no stp on the CISCO's? These are 2900's and 3500's. None of my current setups have more than one path from switch to switch. I use a 4108gl in my cores with all IDF's comming to it via fiber. some closets have more than one switch. They would uplink to the core in the IDF which then fibers to the main IDF. I also tried to read the RSTP PDF but was left rather confused. But I did note that it seemed to state that all switch to switch ports should be set as end points in the RSTP config. true?

[Bruce Campbell_3]

You can probably handle the DHCP problem with spanning tree on the Cisco 2900/3500 switches by setting "spantree portfast" on client ports. That allows the port to go into forwarding mode immediately, rather
than waiting the 30 seconds for the protocol
to complete. But don't set "spantree portfast" on ports connected to other
switches.

I think a mixed environment with some
switches running stp and some rstp is
fine, but I have not tried that.

If you turn spanning tree off altogether on
some switches, that is fine too (apart from
the loss of loop prevention). Some switches will end up being their own
spanning tree domain, if the upstream switch
has spanning tree disabled. But that
is fine.