|
XakEp posted:STP stuff Without seeing what the actual errors were, "Extensive memory errors" is most likely bad hardware. 1. STP is just a protocol that lets a bunch of switches/bridges that are connected together turn off redundant paths so that a frame can't end up circling around in an endless loop. It takes about 30 seconds or so for that to happen when you turn a port on, so if you don't have any loops in your L2 network, you can disable STP to avoid the wait. Turning it off doesn't turn a switch into a hub. You just get a nasty surprise if create a loop. There's not another protocol that replaces it, just other flavors of STP. 2/3. If you've had your network running for a long time, I'd be pretty surprised to suddenly get an STP loop out of the blue. 4. Um... if you looped two ports on the same switch together you could do it. But seriously, different switches might have different symptoms (high CPU/no symptoms other than loss of traffic) depending on what type of frame is looping. In any case, the explanation you got doesn't sound right.
|
#
¿
Aug 1, 2007 15:41
|
|
|
|
| # ¿ Apr 28, 2024 00:17 |
|
|
XakEp posted:Having never disabled STP on a switch, I have no idea what would happen, but looking through cisco's site I cant really get a clear idea of what would happen. Imagine you have two switches (A and B) connected to each other with a single link and two PCs (1 and 2) connected to switch A. PC #1 ARPs or somehow sends an L2 broadcast. It goes to switch A, which needs to send it to all its ports. It gets sent to both switch B and to PC #2. Switch B gets the frame and sends it to all its other ports. If you have spanning tree turned on in this scenario and plugged in a new PC or attached another switch, you'd have to wait for STP to converge (about 30 seconds or so) before traffic would be allowed to go through it. But since you don't have any loops, you can turn it off and can send traffic as soon as something is plugged in. Now lets take the same example and add a redundant connection between switch A and B. There's now a loop in your network. PC #1 ARPs again and switch A gets it. He now has 3 links to send it out, one to PC #2, and 2 that go to switch B. Switch B gets one of the frames and sees that he has a link to switch A that he needs to forward the broadcast to. The frame now goes back to switch A. Switch A gets it and sees that he's got links to broadcast it to, etc... You've now got traffic circling around forever. If you have STP turned on, A and B would talk to each other and one of them would end up blocking traffic from going in or out one of the ports. Let's say switch A blocks one of the ports going to switch B. When switch A gets the first packet, he sends it to switch B on the unblocked port. Switch B gets it, but he still has two forwarding connections to switch A. He sends it back to switch A on the 2nd port, but since A has blocked the port, it won't receive it, breaking the loop. I hope that kind of makes sense. It's hard to visualize without a diagram. Basically, if you connect a whole bunch of switches together and turn on STP, it figures out the minimum spanning tree that gives you one and only one path to every other switch. If you ever disconnect something or add another connection, it dynamically changes the tree for the new network.
|
|
#
¿
Aug 1, 2007 16:17
|
|