Spanning-Tree attempts to detect network loops by looking for special kinds of packets that only switches generate. So typically you would enable portfast on your access ports, ports that are connected directly to hosts, but not on your uplink ports, ports connected to other switches.
On Fri, Jan 11, 2013 at 2:00 PM, <[email protected]> wrote: > > On Fri, 11 Jan 2013, John Stoffel wrote: > > Richard> Hi! I have a problem that I was hoping I could get some >> Richard> advice on. In particular, where to start looking... >> >> Richard> I inherited a Rocks Cluster which I am trying to make >> Richard> semi-usable. There are 31 nodes in the cluster, so in order >> Richard> to create the cluster network, two Dell switches are used -- >> Richard> a PowerConnect 5224 and a PowerConnect 5324. The head node >> Richard> and most of the computer nodes are plugged into the 5224, and >> Richard> the rest are plugged into the 5324 which then is plugged into >> Richard> the 5224. The problem that I'm having is that the clients on >> Richard> the 5324 cannot be PXE booted properly. If I plug them into >> Richard> the 5224, let them boot and install, and then plug them back >> Richard> into the 5324, they work correctly, until the next time I >> Richard> need them to reboot (to add a package, or something). >> >> Richard> I assume there is some kind of packet that is not being >> Richard> properly forwarded by the 5324 (or not being allowed by the >> Richard> 5224). What I would like is to convince the two switches that >> Richard> they are really one big(ger) switch, so they don't block >> Richard> anything from going around. Unfortunately, I really don't >> Richard> know much about networking beyond the basics -- in >> Richard> particular, I don't know the terminology. Looking at the >> Richard> configurations of the switches, I see things like >> Richard> "spanning-tree", "bridging", "trunks", etc. >> >> Richard> What should I be looking at? I tried to Google various >> Richard> things, but I'm not convinced I even know where to start -- >> Richard> at least, nothing I've found seems to address my question, or >> Richard> at least make sense to me. >> >> Try checking that port-fast is/isn't turn on for the ports. We have a >> problem here with our DELL 5224s not working right with our Cisco 4507 >> running IOS showing the same symtoms. So far I haven't beaten on it >> enough to chase down the real config issue, mostly because I only >> kickstart once in a while and I don't run the switch and don't want to >> run the switch. >> > > John makes an excellent point about portfast. You want that turned on for > hosts (or routers) so that their links come up quickly (it speeds up the > Spanning Tree algorithm by cutting out or shortening some of the steps). > > You almost never want portfast enabled on a link that goes to a switch, > trunk or not, as the risk of loops is much higher. I don't think the Dell > switches even let you do that on a trunk, but a Cisco switch will let you > and it does have its uses. > > -Nate > > > Nate also has some good thoughts here, and more details too. Good >> luck. >> >> John >> ______________________________**_________________ >> Discuss mailing list >> [email protected] >> https://lists.lopsa.org/cgi-**bin/mailman/listinfo/discuss<https://lists.lopsa.org/cgi-bin/mailman/listinfo/discuss> >> This list provided by the League of Professional System Administrators >> http://lopsa.org/ >> >> ______________________________**_________________ > Discuss mailing list > [email protected] > https://lists.lopsa.org/cgi-**bin/mailman/listinfo/discuss<https://lists.lopsa.org/cgi-bin/mailman/listinfo/discuss> > This list provided by the League of Professional System Administrators > http://lopsa.org/ > -- Perfection is just a word I use occasionally with mustard. --Atom Powers--
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