Let’s say I’ve a 24 port CRS3xx switch that has also some router capabilities.
Some examples I saw in some forum postings indicate that one can assign a subnet to a port of such a switch device.
Does this mean that one then can attach for example a cheap 8-port unmanaged/dumb switch to that port, and by this action effectively extend the total port number to 32 (actually 30) ?
If that’s indeed possible, then what are the drawbacks of this method besides the fact that these new ports have to share the one uplink when they want to access the rest of the net?
You can of course attach an 8-port switch to one of 24 ports on MT, in that case you’ll have 24-1+8 available ports (one for uplink to the plain switch won’t be of any use).
Each MT port is separately manageable, take into consideration when you connect plain switch you won’t have same manageability for each port. The policy and rules you set for the uplink port will apply all ports on 8-port switch.
Ok, thank you for the confirmation. Yes, and also the traffic within that secondary switch device does usually not reach the first switch; only if they want to go outside of that secondary switch.
Just a minor fix: the formula must be 24-1+8-1 = 30, as a port on each of the both devices gets used for connecting them together.
The general formula is (for linux “bc” calculator):
p = 24 ; q = 8 ; n = 1 ; (p-n)+(n*q-n)
where:
p = # of ports of the CRS switch device
q = # of ports of the secondary switch device
n = # of secondary switch devices; this must be 0..p
Some example calcs for 8-port secondary switches (ie. that much enduser-ports in total in various subnets (n + (n < p)) are then possible):
p = 24 ; q = 8 ; n = 0 ; (p-n)+(n*q-n)
24
p = 24 ; q = 8 ; n = 1 ; (p-n)+(n*q-n)
30
p = 24 ; q = 8 ; n = 24 ; (p-n)+(n*q-n)
168