> ------------------------------ > > Message: 3 > Date: Sat, 7 Jun 2008 17:50:59 +0200 > From: "Pavel Skovajsa" <[EMAIL PROTECTED]> > Subject: [c-nsp] Maximum switched ethernet daisy chain size > To: [email protected] > Message-ID: > <[EMAIL PROTECTED]> > Content-Type: text/plain; charset=ISO-8859-1 > > Hello all, > Recently I have found an interesting issue. > I have found that on our network the packets that traverse more then > 17 (18 and more) L2 ethernet switching hops all connected with MM > fiber 1G links have lowered probability of arrival. > The way I have found this is that our big ethernet ring with 30+ > switches was cut (fiber issue) behind 18th switch from L3 switch, and > everybody hosted after 18th switch has some interesting packet loss > issues.See the smokeping details for 18th switch on > http://img171.imageshack.us/img171/3777/hop18kn4.jpg. > > This is not very logical for me, as switched ethernet works based on > store&forward method so no old-school 5-4-3 rule applies as in shared > collision (hub) environment. Anybody has a good explanation why adding > more L2 hops to the path tends to kill packets? > > Regards, > Pavel > > p.s. yes I know that building large ethernet rings is generally not a > good idea, however sometimes due to large distances you have no other > choice > >
This sounds like a spanning-tree diameter problem. Spanning-tree limits the number of intermediate switches between the root and each end-point. Without tuning this value is 7. This link describes possible issues with diameter: http://www.cisco.com/warp/public/473/16.html#awkward This link may help you resolve the problem: http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094954.shtml -- LR Mack McBride Network Administrator Alpha Red, Inc. _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
