...please can someone explain this to me before my brain melts, and if this is obvious I deserve a slap, but long day!
I was at a customer site replacing an old managed switch that was put in by another company with a new Cisco SF300.
Now, the router is a Cisco 881, which has 4 L2 switchports and an ethernet WAN port.
From what I saw, there were two links going in to the switch from F0 and F3. I thought this might have been an etherchannel or just STP in action.
Anyway I replaced the 3COM switch with our one and plugged F0 in to one of the gigabit ports on the primary SF300. I checked the router config and the switch and there was nothing special at all, no etherchannels, nada. Anyway I plugged F3 in to the second gigabit port same as on the 3COM and it...just worked. I checked STP, both were forwarding. It's like it was doing load balancing.
Now for all the world I thought that would produce a switching loop, and STP would kick in and block the second link. I checked the frame counters on both ports and they were increasing at about the same rate, load balancing.
What am I missing.
p.s I apologise if this is a stupid question in advance.
