Date: Sat, 12 Jun 2010 14:22:52 -0700 From: Kurt Buff <kurt.buff@gmail.com> To: freebsd-net@freebsd.org Subject: Re: VLANs, routing, multicast and HP switches, oh my... Message-ID: <AANLkTin8Tmcz19rPgjma6Pj_O0vpG7LfZkWkDskLT3zj@mail.gmail.com> In-Reply-To: <huqr8u$uak$1@dough.gmane.org> References: <AANLkTikZhyrufjNuUPhNDlDZ4iKp-KWN-AgcwUt1g1_p@mail.gmail.com> <huqr8u$uak$1@dough.gmane.org>
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On Thu, Jun 10, 2010 at 07:02, Ivan Voras <ivoras@freebsd.org> wrote: > On 06/09/10 22:35, Kurt Buff wrote: >> All, <snip> >> Now, however, the subnet on fxp4 is going to have an HP 2610 switch >> attached to it, and they want to hang multiple subnets from that >> interface. > > ... which doesn't necessarily translate to VLANs. You can assign an > arbitrary number IP addresses to a single NIC without problems. True - but they are apparently going to be simulating hundreds of machines on two subnets, as I found out a day later. Sorry for the late reply - been slammed at work. >> So, it looks to me as if I need to set up this box with a VLAN >> configuration and some more routing intelligence than it has at the >> moment. >> >> I'm looking at, among other pages, this one >> http://www.cyberciti.biz/faq/howto-configure-freebsd-vlans-with-ifconfig-command/, >> though I don't see much addressing these two subjects in the handbook. > > There's not much to say on the topic. The section which describes VLAN > setup in the link you have given is correct. Each new virtual vlan > device will behave as another NIC. Good to know. Thanks for that. > The story behind VLANs is that they are an Ethernet-level routing > kludge. Instead of having a flat topology, they divide it into chunks > which may be routed separately on L2. Yep - do that with my HP switches in the rest of the environment. > On the FreeBSD side, the > representation of this will be additional NICs which operate only on > these "chunks" - virtual Ethernets which don't see packets from other > VLANs even if they travel on the same wire(s). The physical NIC will > need to "see" all packets indiscriminately (which is sometimes called a > "trunk"), and the OS logic will then "divide" those packets into > individual virtual vlan devices. Note that if you use VLANs, all active > equipment involved will probably need to be able to understand and work > with VLANs, and you will need to configure them all. To be able to use > generic Ethernet clients (like Windows with low-end NICs), some kind of > end-point equipment will need to strip VLAN tags before the packets > reach them. > > But as I've said, maybe you don't need VLANs. Simply hang multiple IP > subnets on normal Ethernet NICs. Again - they'll be putting up to 200 busy machines on each subnet. It seems reasonable to limit the broadcast domains with VLANs. Thanks for the feedback. Kurthome | help
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