On Fri, Jun 15, 2007 at 01:58:22PM +1200, Brett Davidson wrote: > Steve Holdoway wrote: > >On Fri, 15 Jun 2007 13:47:12 +1200 > >Robert Fisher <[EMAIL PROTECTED]> wrote: > > > > > >>On Friday 15 June 2007 1:14 pm, David Kirk wrote: > >> > >> > >>>Robert's point about only being able to daisy chain up to 2 switches > >>>is incorrect. > >>> > >>No I said 3 (three) but I cannot find documentation to back up what I had > >>thought. > >> > >> > >>>Our network has at least 10 switches all linked > >>>together with redundant links. > >>> > >>I think the following is OK.......... > >> > >>P S----------------------------Switch2--------------------Switch3 > >>R W---------------------------Switch4--------------------Switch5 > >>I I----------------------------Switch6--------------------Switch7 > >>M T---------------------------Switch8--------------------Switch9 > >>A C---------------------------Switch10------------------Switch11 > >>R H---------------------------Switch12------------------Switch13 > >>Y > >> > >>but not............ > >> > >>S-------Sw2------Sw3-----Sw5----Sw6------Sw7----Sw8------Sw9-----Sw10 > >>W-----------Switch4 > >>I > >>T > >>C > >>H > >> > >>Happy to be corrected though as it could make life easier at times. > >>Where is Michael Moffat? (He works at Allied Tellyson)
I've been trying to stay way the hell away from this one, there's more inaccuracies in this thread than I could possibly deal with. One problem is that people are mixed up about the differences between hubs and switches. The thread is really one for the linux list. > >> > >>Rob > >> > >> > >I think you're confusing best practices with actually supported. Obviously > >the available bandwidth plummets with each switch, but networking limits > >revolve around cable, not equipment ( eg max cat 5 run = 100m - but you > >can run 200m if there's a switch in the middle, etc ) to the best of my > >knowledge. I recall that Cisco used to say 7 when I did the CCNA / CCNP stuff, but in all reality it is as many as you can get away. It also depends on whether you are using hubs or switches. There's also the matter of duplex, technically a true hub is half duplex and does not learn where MAC addresses are. So when you have lots of hubs you really do have one very large network. > > > >Steve > > > >Steve > > > Yup. > The next limit after that comes from the infamous 543 rule. > You can have 5 segments of cable seperated by 4 pieces of equipment of > which ONLY 3 segments are allowed to have other devices (that is, other > than the interconnecting segment devices) on them. I recall that Cisco used to peddle this theory. What I see in the real world is some network setups that certainly don't conform to this design idea and certainly do work. > The reason for all of this is, as Steve says, cable-related. The total > maximum length of cable must allow a packet to make a complete round > trip of the entire network within the lifetime of that packet else > network collisions can't be detected. > (Yup, even in the days of switches, we're still constrained by collisions). You need to be careful, there's FUD in this. In the case of switches, cable lengths are irrelevant until the switch to switch connection gets to about 100 metres. Each switch-to-switch or switch-to-PC connection (and I am talking about switches) is a segment and so each segment is a collision domain in itself. For the reason I mentioned earlier, your network of hubs is one large collision domain. In fact, collisions are a contraint of ethernet, not switches. But we are talking about ethernet here AFAIK. Don, a couple of hubs connected together will be fine, don't sweat it. Your concern is the size of the collision domain. So the more hub ports, the more likely the collisions and the resultant degradation to network performance. Lastly, switches keep tables of MAC addresses as someone correctly observed, but they incorrectly stated that this was the reason for the chain limitation. Switches can store thousands of MAC addresses. They do this so that they know where each host is. We very rarely see networks exhaust MAC storage, but it does ocassionally happen. It won't happen to Don. Cheers, Michael. > > Brat. > > -- > -- > -- > Brett Davidson > Systems Engineer > -- > Net24 Limited > Web: www.net24.co.nz > Phone: 0800 5000 24 | DDI: +64 3 962 9511 > -- > // domain names / email hosting / web hosting > // our reputation for reliability precedes us >
