We had a bad weekend a couple of month ago when every 24 minutes our LAN would pretty much vanish for about 30-60 seconds. It turns out what truly appeared to be a workgroup switch was actually a hub. One Friday afternoon it decided to show us all why hubs do not belong in networks.
-- richard -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Kurt Buff Sent: Friday, September 20, 2013 1:12 PM To: [email protected] Subject: Re: [NTSysADM] Semi-OT: Network problem On Fri, Sep 20, 2013 at 11:03 AM, Ben Scott <[email protected]> wrote: > On Fri, Sep 20, 2013 at 12:58 PM, Kurt Buff <[email protected]> wrote: >> ... core layer3 switch ... spikes its CPU to 99% during these episodes ... >> ... Volume of traffic is normal ... > > CPU spikes on a switch is usually something "weird". Normal traffic > is handled in the switch ASIC and doesn't touch the CPU at all. > Typically it's things like ACLs or policy routing that hit the CPU. > Got anything like that going on? > >> ... layer2 loop ... > > A layer two loop will light up every switch port on the first > broadcast packet (or trigger loop detection, which should get logged), > so I don't think that's it. No, the configuration of the L3 switch is stupidly simple - I've got all of my servers plugged into it, and all of my distribution switches. It's got 34 of VLANs defined (max-vlans is set to 100), and it's x.x.x.1 on every subnet except the L2 VLAN that terminates on the firewall. I've got 4 x 4-port trunks on it (3 for my VMware boxes and one for the backup machine - the backup machine's trunk is LACP, the others are not, since VMware doesn't support LACP). No particular changes to the config in months (when I set up the LACP trunk for the backup machine. No ACLs, and two routes - a DG and a static to another switch for a lab subnet. Kurt The information contained in this e-mail, and any attachments hereto, is from The American Society for the Prevention of Cruelty to Animals® (ASPCA®) and is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution, copying or use of the contents of this e-mail, and any attachments hereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify me by reply email and permanently delete the original and any copy of this e-mail and any printout thereof.
