Why does this appear/occur every 2 seconds on my network? Is it really necessary for it to occur every 2 seconds? asked 29 Jan '13, 09:18  cherokee edited 29 Jan '13, 09:22  SYN-bit ♦♦ |
2 Answers:
If you need spanning-tree in your network depends on your network topology. If you only have one switch (or a switch-stack), then you probably don't need it (unless you are afraid people will connect two ports by accident). You can configure your switches to not use spanning-tree to get rid of these packets. But if you do need spanning-tree because you have multiple paths between switches, then yes, you need these messages in your network to do the loop detection and automatic reconfiguration of your switches in case a link fails. answered 29 Jan '13, 09:26 SYN-bit ♦♦ |
By the way, Spanning Tree was developed to prevent layer 2 loops from occurring. In IP world, the TTL field can be used to prevent packets from looping around forever. However, there is no such field in an Ethernet frame. As a result, if you create a L2 loop, the frames will fly around infinitely. Creating a L2 loop is a great way to test the "real throughput" of any switch! :) Spanning tree's job is to make sure that there is only one path to the root bridge (king of the hill). this way, even if you have redundant uplinks (not part of etherchannel) you are guaranteed not to have loops at layer 2. That's the sole purpose of spanning tree. Insuring that your L2 network is loop free. answered 29 Jan '13, 19:44  hansangb edited 30 Jan '13, 00:07  grahamb ♦ oops! Thanks Graham! I left the not out, I take it? :) (30 Jan '13, 16:23) hansangb I changed a "look" into "loop". (30 Jan '13, 23:47) grahamb ♦ |
not to forget - "every 2 seconds" is an eternity in today's networks, so apart from sometimes being annoying in the packet list, BPDU frames do not hurt the network bandwidth.
It's like car insurance. You don't need it until you need it! So don't disable spanning tree. It's so insignificant that it's not even a packet....it's just a frame! :)