Hazelsnitzel wrote: > At 10:24 AM 1/24/2007, you wrote: >> Hazelsnitzel wrote: >>> Greetings, >>> My task leader wants to use a 24-port Cisco Catalyst 2950 in >>> conjunction with a Linux box to emulate multiple low-speed links, but >>> I am too much of a novice at networking and VLANs to know whether his >>> idea is feasible. >>> We currently emulate a single low-speed link by interposing a Linux >>> box with two NICs between the endpoints on the link. We use the >>> Linux box as a bridge and use Linux traffic control (i.e., tc HTB or >>> TBF) and "Netem" to emulate link characteristics. Eleven Linux boxes >>> would be required to emulate 11 low-speed links. My task leader's >>> idea is to use a single "one-armed" Linux box and the 24-port 2950 to >>> emulate up to 11 links. >>> The intranet in our lab uses OSPF and we are not allowed to increase >>> the number of router advertisements, so we can't use the Linux box as >>> a router. However, if this constraint were removed, I assume (#1) >>> that we still couldn't use the Linux box as a router because both >>> endpoints of each link are always in the same subnet. Is this >>> assumption correct? >>> I also assume (#2) that we can't use the Linux box as a bridge. I >>> assume that if the traffic emanating from the bridge were simply >>> returned to it on a trunked link, it would only forward frames to the >>> destination if the source and destination MAC addresses were in the >>> same VLAN. >>> I would like to know if my two assumptions are correct and whether >>> anyone has a suggestion about how to solve this problem. Could it be >>> done by developing some custom forwarding software? If so, what >>> would be required? >> >> It can be done. We offer a product based on VLANs and our >> (non-open-source) >> network emulation tool. >> I'm not sure if netem can be used in bridge mode though... >> >> Here's a link to our 48-port network emulator product sheet (we offer >> other >> quantities of ports as well): >> http://www.candelatech.com/lanforge_v3/ct970_product.html >> >> The diagram shows one LANforge machine and one bridge machine, but we can >> now do all of this in a single machine for a more efficient use of >> hardware. >> >> If you are interested in more information related specifically to >> LANforge, >> please contact me directly (greearb@xxxxxxxxxxxxxxx). >> >> Thanks, >> Ben >> >> >>> Thanks, >>> Bob >>> _______________________________________________ >>> Vlan mailing list >>> Vlan@xxxxxxxxxxxxxxx >>> http://www.candelatech.com/mailman/listinfo/vlan >> >> >> -- >> Ben Greear <greearb@xxxxxxxxxxxxxxx> >> Candela Technologies Inc http://www.candelatech.com >> >> _______________________________________________ >> Vlan mailing list >> Vlan@xxxxxxxxxxxxxxx >> http://www.candelatech.com/mailman/listinfo/vlan > > > Ben, > > Thanks for your reply. > > My task leader has already purchased the Catalyst 2950 and a Dell > PowerEdge so we need to try to make it work with this hardware. > > > [ Catalyst 2950 ] > [ Linux Bridge ]--[eth0]--[trunked]---[ Port 1 ] > +-------[eth1]--[trunked]---[ Port 2 ] > VLAN 2 [ Port 3 ]---- 192.168.2.3 > VLAN 3 [ Port 4 ]---- 192.168.2.4 > VLAN 4 [ Port 5 ]---- 192.168.3.3 > VLAN 5 [ Port 6 ]---- 192.168.3.4 > ..... ..... .......... > > In this configuration, VLANs 2 and 3 emulate one link and VLANs 4 and 5 > emulate another. > > Will this configuration work? Are there any adverse consequences to having > two trunked links as shown? I've seen problems with cisco switches in our configuration because they look at source-mac before the VLAN tag, and complain about the same MAC on different ports (even though the ports are on different VLANs, so it shouldn't matter.) We've used Netgear managed ethernet switches...they just work right out of the box. There are ways to configure cisco switches to work in this manner, but I do not know what they are (I just watched a cisco guru fiddle with it until it worked.) Other than that, I believe your idea is sane. Thanks, Ben > > Regards, > Bob > _______________________________________________ > Vlan mailing list > Vlan@xxxxxxxxxxxxxxx > http://www.candelatech.com/mailman/listinfo/vlan -- Ben Greear <greearb@xxxxxxxxxxxxxxx> Candela Technologies Inc http://www.candelatech.com
