* Jussi Peltola <pe...@pelzi.net> [2010-05-20 20:07]: > On Thu, May 20, 2010 at 07:28:55PM +0200, Henning Brauer wrote: > > * Graham Allan <al...@physics.umn.edu> [2010-05-20 19:23]: > > > On Thu, May 20, 2010 at 07:02:23PM +0200, Axel Rau wrote: > > > > Am 20.05.2010 um 00:04 schrieb Henning Brauer: > > > > > > > > >* Axel Rau <axel....@chaos1.de> [2010-05-19 10:34]: > > > > >>Now the question: Can I put a trunk on top of a carp? > > > > > > > > > >you put carp on top of the trunk of course. > > > > OK. > > > > Can I have a trunk connected to 2 different switches then? > > > > > > Not normally. Some higher-end switches can support this, eg the > > > HP Procurve switches running their K-series software can do something > > > they call distributed trunking (and no doubt Cisco and other vendors all > > > call it something else). But as I think you were talking about using > > > cheapish Netgear switches it's unlikely to be possible. > > > > well, lacp usually doesn't work across switches. but lacp is not the > > only mode trunk supports. roundrobin definately works across switches > > - how well might depend on your switches. works well for me on > > procurve with E-series software which doesn't do distributed trunking > > afair.< > > How about the warnings about packet reordering and interactions with > TCP?
never ran into such issues. too lazy right now to check wether trunk deals with that in roundrobin or wether i just got lucky. > I'd guess it's not really such a big issue if you have two > identical switches and routers. But shouldn't the hash based trunk modes > work just fine, too (with the caveat that some flows will stop working > completely if the other switch fails in some ways while roundrobin will > cause half of the packets to be blackholed, keeping badly degraded > connectivity) err. wait. if the switch fails for real the link goes down and the port is just taken out of the active ports on the trunk. now there are of course more subtle ways of failure that could lead to the above scenario. but how likely is that really? and would this issue be your real problem then? > Also, the switches need to be separate; connecting them directly may > cause learned MACs to flap between the real host port and the cable > between the switches and make the trunk receive its own traffic on the > other port. that is the "may depend on your switch" part. I have not seen any problems with interconnected procurves, 5300XL series. > Fail-over trunk should work just fine, too. indeed. > If you want reliability, do not use cheap switches. Switch power > supplies are not the failure mode you want to avoid. I don't remember > seeing very many at all, however I've seen lots of crappy ones lose > their config or stop forwarding completely while keeping the link up. guess i lack the cheap shit switch experience. i do have experience with expensive shit switches tho. they suck in many different ways, never seen the behaviour you describe above tho. but then, ever since using said procurves, that is history. > I have two identical "core" switches in one (not really so critical at > all) place running OSPF, with a bunch of routers connecting to both > switches for redundancy. Works pretty well and there has even been a > config reset incident, which didn't break anything - because OSPF can > detect link failures. Trying to do the same all the way to the end hosts > (i.e. without a routing protocol) is pretty difficult. i would never ever run any L3 on switches. > However, if you need to ask if you can run a trunk on top of a carp, do > yourself a favor and use a single switch. There will be less downtime. that is something i could subscribe to :) -- Henning Brauer, h...@bsws.de, henn...@openbsd.org BS Web Services, http://bsws.de Full-Service ISP - Secure Hosting, Mail and DNS Services Dedicated Servers, Rootservers, Application Hosting
