Hi, just a question in advance: do you know for sure that STP BPDUs are forwarded "across the cloud"? [this may or may not be the case, depending on the gear used and the configuration/carrier (you?) providing the VPLS links]
On Tue, Mar 25, 2008 at 09:47:16AM +1300, Pshem Kowalczyk wrote: > Hi, > > It looks like one of our customers would like to have redundant L2 > access. We have two PEs in both locations so in theory that should > work. However, I wonder what your ideas are about preventing L2 loops > in such network. The customer envisaged something like this: > (variable-width font): > > CSW1----CSW2 > | | > PE1 PE2 > > MPLS cloud > > PE3 PE4 > | | > CSW3---CSW4 > > where CSW is the customer's switch. Currently they only have one half > of that solution (CSW1, PE1, PE3 and CSW3) with a single VPLS between > PE1 and PE3. > > The solution we came up with is to run single VPLS1 between PE1 and > PE3 (the way it is now) and then add VPLS2 between PE2 and PE4. This > way customer can run spanning tree if I understood you correctly there will be two different "VPLS clouds" between both pairs of CSW/PE links? why run STP at all, then? (bearing in mind that if they set > the cost incorrectly they will get CSW3 talking to CSW4 through CSW1 > and CSW2). again: given two different clouds this shouldn't happen. furthermore I seem to recall a Cisco white paper discussing ways (though impractical ones, from my perspective) to avoid loops in VPLS scenarios: http://www.cisco.com/en/US/tech/tk436/tk891/technologies_white_paper09186a00801f6084.shtml thanks, Enno -- Enno Rey Check out www.troopers08.org! ERNW GmbH - Breslauer Str. 28 - 69124 Heidelberg - www.ernw.de Tel. +49 6221 480390 - Fax 6221 419008 - Cell +49 173 6745902 PGP FP 055F B3F3 FE9D 71DD C0D5 444E C611 033E 3296 1CC1 Handelsregister Heidelberg: HRB 7135 Geschaeftsfuehrer: Roland Fiege, Enno Rey _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
