Thanks....Re: [RE: Too many broadcasts [7:453]
"Chuck Larrieu" wrote: Broadcasts are not necessarily bad. How do you suppose ARP works? Not to mention all the things that make life under windows so enjoyable? Such as network browsing? Do not be so hasty. Understand first. How many servers? How many pc's? all on one flat network? No VLANs or inter-vlan routing? Chuck Once worked in a brokerage firm where during market hours 90% of my traffic was broadcast - and a good thing, too! -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Infotech Sent: Thursday, April 12, 2001 10:17 PM To: [EMAIL PROTECTED] Subject:Too many broadcasts [7:453] Dear Group, I have a small query: Is it advisable to disable broadcast on all the ports of switches. I have 3 catalyst series 6509/5500/5505 in my network running all the WINNT servers 4.0 with all win98/win95 as clients. With the help of CWSI I have observed that many a times the broadcast increases very much & I experience lot of response delay in my network. can I use the command: switch> (enable)# set port broadcast 0% Will this put any impact on my network like nodes won't be able to talk to server or problem in finding the servers. I have also created VLAN's in my network to limit the broadcasts. Should I doit on all the ports... many thanks in advance HP Get free email and a permanent address at http://www.netaddress.com/?N=1 FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get free email and a permanent address at http://www.netaddress.com/?N=1 Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=3022&t=453 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Too many broadcasts [7:453]
At 01:16 AM 4/13/01, Infotech wrote: >Dear Group, > >I have a small query: > >Is it advisable to disable broadcast on all the ports of switches. I have 3 >catalyst series 6509/5500/5505 in my network running all the WINNT servers >4.0 >with all win98/win95 as clients. With the help of CWSI I have observed that >many a times the broadcast increases very much & I experience lot of response >delay in my network. >can I use the command: > >switch> (enable)# set port broadcast 0% Setting the threshold to zero would be a misuse of the Cisco broadcast suppression feature. I'm not sure Cisco even lets you set it to zero? It would also cause network problems since you need broadcasts for such important functions as dynamic address assignment, address and name resolution, service location, and service advertisement. ARP, DHCP, Cisco Discovery Protocol, RIP, EIGRP, OSPF, IGMP, and NetBIOS are some of the many protocols that make use of broadcasts and multicasts. The goal of the broadcast suppression feature is to prevent broadcast storms, not broadcasts in general. A broadcast storm occurs when bugs in a protocol-stack implementation or in a network configuration cause a station to send hundreds or thousands of broadcasts per second. In the worst case, the broadcasts from one station result in other stations also sending broadcasts, much like a storm that builds upon itself. Broadcasts can cause problems because they interrupt every device in the broadcast domain, causing a CPU interrupt and requiring processing. On slow CPUs, broadcast storms can be a serious problem. Broadcast storms can wreak havoc on 100-Mbps Ethernet LANs with slow computers, because misbehaving devices have an opportunity to send broadcasts really quickly at 100 Mbps. You can configure broadcast suppression on a switch port to keep excessive broadcasts from causing performance degradation on devices or LANs reachable from that port. Cisco implements broadcast suppression in software or hardware, depending on the switch platform. Software broadcast suppression uses a packet-based method. Hardware broadcast suppression uses a bandwidth-based method. When a packet-based method is used to measure broadcast activity, the threshold parameter is the number of broadcast or multicast packets received over a one-second time period. When a bandwidth-based method is used, the threshold parameter is the percentage of total available bandwidth used by broadcasts or multicasts. In either case, if the threshold is reached, the switch port cuts off broadcast and multicast packets for the rest of that second. Because packet sizes vary, bandwidth-based measurement is more accurate and more effective than packet-based measurement. As Howard often points out, broadcast packets are usually short and don't use much bandwidth. In addition, most normal applications don't broadcast thousands of times in a second. (For a station to use up most of 100 Mbps with 64-byte packets, it would need to send approximately 200,000 times per second, which is obviously abnormal.) So, when broadcasts start to use a lot of your available bandwidth in a one-second interval, this probably indicates a serious problem. So, to make a long story short, a proper setting for the threshold parameter would probably be more like 75%. The value depends on your actual applications and traffic types. Priscilla >Will this put any impact on my network like nodes won't be able to talk to >server or problem in finding the servers. I have also created VLAN's in >my >network to limit the broadcasts. Should I doit on all the ports... > >many thanks in advance >HP > > > > >Get free email and a permanent address at http://www.netaddress.com/?N=1 >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=510&t=453 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Too many broadcasts [7:453]
U, no, it's not advisable to disable broadcasts if you want ARP to work. ARP not working would cause rather severe problems. :-) doctorcisco >From: "Infotech" >Reply-To: "Infotech" >To: [EMAIL PROTECTED] >Subject: Too many broadcasts [7:453] >Date: Fri, 13 Apr 2001 01:16:44 -0400 > >Dear Group, > >I have a small query: > >Is it advisable to disable broadcast on all the ports of switches. I have 3 >catalyst series 6509/5500/5505 in my network running all the WINNT servers >4.0 >with all win98/win95 as clients. With the help of CWSI I have observed that >many a times the broadcast increases very much & I experience lot of >response >delay in my network. >can I use the command: > >switch> (enable)# set port broadcast 0% > >Will this put any impact on my network like nodes won't be able to talk to >server or problem in finding the servers. I have also created VLAN's in >my >network to limit the broadcasts. Should I doit on all the ports... > >many thanks in advance >HP _ Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=464&t=453 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Too many broadcasts [7:453]
Broadcasts are not necessarily bad. How do you suppose ARP works? Not to mention all the things that make life under windows so enjoyable? Such as network browsing? Do not be so hasty. Understand first. How many servers? How many pc's? all on one flat network? No VLANs or inter-vlan routing? Chuck Once worked in a brokerage firm where during market hours 90% of my traffic was broadcast - and a good thing, too! -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Infotech Sent: Thursday, April 12, 2001 10:17 PM To: [EMAIL PROTECTED] Subject:Too many broadcasts [7:453] Dear Group, I have a small query: Is it advisable to disable broadcast on all the ports of switches. I have 3 catalyst series 6509/5500/5505 in my network running all the WINNT servers 4.0 with all win98/win95 as clients. With the help of CWSI I have observed that many a times the broadcast increases very much & I experience lot of response delay in my network. can I use the command: switch> (enable)# set port broadcast 0% Will this put any impact on my network like nodes won't be able to talk to server or problem in finding the servers. I have also created VLAN's in my network to limit the broadcasts. Should I doit on all the ports... many thanks in advance HP Get free email and a permanent address at http://www.netaddress.com/?N=1 FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=455&t=453 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
