As well as it should when you're transferring 100's of megabytes of data; it's not exactly like downloading a web page. That's where CAR rears its ugly face, no?
WAYNE BAETY, MCSE, A1C, USAF Network Systems Trainer -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Friday, October 26, 2001 1:52 AM To: [EMAIL PROTECTED] Subject: Re: MAC address and VLANs [7:23950] I couldn't agree more on this issue, Jeff. Norton's Ghost is Notorius for hogging much of the backplane bandwidth on CAT5500s during a unicast TCP session. John Squeo Technical Specialist Papa John's Corporation (502) 261-4035 "jeffrey wang" cc: Sent by: Subject: Re: MAC address and VLANs [7:23950] nobody@groupst udy.com 10/25/01 12:08 PM Please respond to "jeffrey wang" Not only VLAN helped solving broadcast problem, but also helped unicast problem. I used to run into problem with some UDP application on a pretty large flat network. When some 100M/full-duplex start talking, 10M workstations were freeze. Sniffer showed me that caused by a unicast storm. Eventually, I learned that if a unicast is sent while switch didn't have or forgot its destination's MAC, it flood. No 100M workstation been affected, but all 10's died. couple second later, it calmed down. (switches started to know where the destination's MAC). However, it happened again and again. VLAN helps first to restrict problem in ONE VLAN, second prevent the switches don't have the VLAN from being affected. Priscilla Oppenheimer wrote: > The multi-VLAN feature that Leigh Anne mentioned might solve your problem. > The Cisco switch port could be associated with two VLANs that way. You > didn't say which switch you have, and this feature may not be available on > all Cisco switches, though. > > Assuming that you don't want to upgrade the little switch to one that does > 802.1Q or ISL, another somewhat radical fix to the problem might be to not > use VLANs. My philosophy is that once VLANs get to the point of causing > more problems then they fix, I eliminate them. ;-) > > One of the main things VLANs were supposed to fix was excessive broadcasts > causing too many CPU interruptions on numerous workstations in a large, > flat, switched network. > > Lately I have taken to making the controversial statement that this problem > doesn't exist on many modern networks. These days workstations have > amazingly fast CPUs. They are not bogged down by processing broadcasts. > Also, as we eliminate older "desktop" protocols such as AppleTalk and IPX, > what is still sending broadcasts? An ARP here or there is not a big > problem. And ARPs don't actually happen that often. A PC keeps the > data-link-layer address of its default gateway and other communication > partners for a long time. > > Also, a lot of PC NICs used to be stupid about multicasts and interrupt the > CPU for irrelevant multicasts for which the PC was not registered to > listen. I bet that bug has been fixed by now. > > VLANs have other benefits (security, dividing up management and > administrative domains, etc.) But if broadcasts are the issue, one should > ask: > > Which protocol send broadcasts and how often? > How fast are the CPUs? > > And that is my latest harangue against my least favorite LAN technology > (VLANs!) > > Priscilla > > At 09:52 AM 10/24/01, NetEng wrote: > >Thanks for the replies. The two MAC addresses would come from the two PC's > >in an office. The would both connect in to a hub and then the hub would > >uplink to the cisco switch. I need one pc in VLAN1 and one pc in VLAN2, from > >what you and Dennis stated this will not work. I appreciate the comments > >though. > > > >Collin > > > >""Leigh Anne Chisholm"" wrote in message > >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Actually, that's not correct. The original specification for VLANs from > > > what I understand mandates that only one VLAN can be assigned to a port, > >but > > > manufacturers such as 3COM decided to do otherwise and support multiple > > > VLANs per port. Cisco responded by creating (on certain switches such as > > > the Catalyst 2900XL) an administrator to configure a port to be a member > >of > > > more than one VLAN at a time when using a membership mode known as > > > "Multi-VLAN". A Multi-VLAN port can belong to up to 250 VLANs; the actual > > > number of VLANs to which the port can belong depends on the capability of > > > the switch itself. Although the concept is similar, this membership mode > >is > > > different than "trunking". The caveat to this feature is that the > > > Multi-VLAN membership mode cannot be configured on a switch if one or > more > > > ports on the switch have been configured to trunk. > > > > > > For more information on this feature, search Cisco's website using the > > > keyword phrase "switchport multi". > > > > > > As for answering NetEng's question--I can't quite determine where > multiple > > > MAC addresses share the same switch port. Could you identify which > switch > > > that is? > > > > > > > > > -- Leigh Anne > > > > > > > -----Original Message----- > > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > > > > Dennis > > > > Sent: Tuesday, October 23, 2001 3:48 PM > > > > To: [EMAIL PROTECTED] > > > > Subject: Re: MAC address and VLANs [7:23950] > > > > > > > > > > > > Cisco will recognize multiple macs on a single port but they must > > > > all be in > > > > the same vlan. Vlan assignment is per port. Your other option > > > > would be to > > > > replace the non cisco hub with a cisco switch which is trunked to the > >main > > > > switch. > > > > > > > > -- > > > > > > > > -=Repy to group only... no personal=- > > > > > > > > ""NetEng"" wrote in message > > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > > Here's my situtation. I have a corporate PC with an IP address of > > > > 10.10.x.x > > > > > and in the same office (and same physical network) another > > > > device with an > > > > IP > > > > > address of 192.168.100.x Both devices are connected to a small > > > > hub/switch > > > > > which in turn is connected to a cisco switch. Can I have the > > > > 10.10.x.x be > > > > > apart of one vlan and the 192.168.100.x be a member of another or the > > > > > default vlan? Can cisco switches recognize multiple MAC addresses on > a > > > > > single switch port (if so, how many?) and be smart enough to know > >which > > > > vlan > > > > > which MAC address belongs to? This would save me hours (otherwise I > >have > > > > to > > > > > run cable for connections to our corporate network and > > > > connections to our > > > > > test network in every cube :-( ). TIA > > > > > > > > > > PS I understand the best way to do this would be to connect each > >device > > > > into > > > > > the cisco switch, but I only have a single cable run to each > >cube/office > > > > > > > > > > > > > > > (corporate pc)10.10.x.x > > > > > | > > > > > PC PC (test network) 192.168.100.x > > > > > | | > > > > > \ / > > > > > \ / > > > > > SWITCH/HUB (non-cisco) > > > > > | > > > > > | > > > > > CISCO SWITCH > > > > > VLANs > > > > > -------- ---------- > > > > > | | | | > > > > > | corp | | test | > > > > > -------- ----------- > ________________________ > > Priscilla Oppenheimer > http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=24193&t=23950 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
