RE: ??? Dumb Consultant ??? - Please Help [7:75213]
Netmasks don't generate traffic, hosts do. :) Thanks, Zsombor Steven Aiello wrote: Hello all, I need some folks with hopefully a CCIE to answer this question. If there is an un subnetted class A, and there are 25 or users on the network. would the fact that the network is unsubnetted cause a large load of network traffic? here is the reason and layout. Our company uses Xerox printers and they came with address 10.6.1.45 - 255.0.0.0 10.6.1.44 - 255.0.0.0 our clients are all on the same network using a DHCP pool of 10.6.1.100 - 10.6.1.150 even if there is broadcast it is one message across the network (lets say for Netbios name resolution) there is one broadcast not a unicast to 16,7xx,xxx some host. Only 25 hosts will answer correct? So how will a class A subnet mask cause this? Thanks for all input, please feel free to ramble, Steve Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=75217t=75213 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: ??? Dumb Consultant ??? - Please Help [7:75213]
Well, I'm not a CCIE, but I don't think you need to be a CCIE to answer this question. The subnet mask has nothing to do with the amount of load on the network. A side effect of having a small network mask is that there are potentially more hosts on the network, which could mean that there is more broadcast traffic, but it's just a side effect; the small network mask doesn't cause the load, the number of hosts does. If you had 25 hosts on a /24 subnet, you would have the same amount of traffic as if you put them on a /8 subnet all else being equal. There are some things that could be different, but again they are side effects. For instance, if you had a network management device that sends ICMP echo requests out to every IP address in the subnet (and resultant broadcast ARPs) then there would be more load on the network. It is suggested that you use the proper mask for subnets though. Fred Reimer - CCNA Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA 30338 Phone: 404-847-5177 Cell: 770-490-3071 Pager: 888-260-2050 NOTICE; This email contains confidential or proprietary information which may be legally privileged. It is intended only for the named recipient(s). If an addressing or transmission error has misdirected the email, please notify the author by replying to this message. If you are not the named recipient, you are not authorized to use, disclose, distribute, copy, print or rely on this email, and should immediately delete it from your computer. -Original Message- From: Steven Aiello [mailto:[EMAIL PROTECTED] Sent: Wednesday, September 10, 2003 7:16 PM To: [EMAIL PROTECTED] Subject: ??? Dumb Consultant ??? - Please Help [7:75213] Hello all, I need some folks with hopefully a CCIE to answer this question. If there is an un subnetted class A, and there are 25 or users on the network. would the fact that the network is unsubnetted cause a large load of network traffic? here is the reason and layout. Our company uses Xerox printers and they came with address 10.6.1.45 - 255.0.0.0 10.6.1.44 - 255.0.0.0 our clients are all on the same network using a DHCP pool of 10.6.1.100 - 10.6.1.150 even if there is broadcast it is one message across the network (lets say for Netbios name resolution) there is one broadcast not a unicast to 16,7xx,xxx some host. Only 25 hosts will answer correct? So how will a class A subnet mask cause this? Thanks for all input, please feel free to ramble, Steve **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=75218t=75213 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: ??? Dumb Consultant ??? - Please Help [7:75213]
Steven Aiello wrote: Hello all, I need some folks with hopefully a CCIE to answer this question. If there is an un subnetted class A, and there are 25 or users on the network. would the fact that the network is unsubnetted cause a large load of network traffic? here is the reason and layout. Our company uses Xerox printers and they came with address 10.6.1.45 - 255.0.0.0 10.6.1.44 - 255.0.0.0 our clients are all on the same network using a DHCP pool of 10.6.1.100 - 10.6.1.150 even if there is broadcast it is one message across the network (lets say for Netbios name resolution) there is one broadcast not a unicast to 16,7xx,xxx some host. True. It will just be one broadcast packet and probably won't use a lot of bandwidth. It may be repeated a few times, but probably still won't use a lot of bandwidth. Only 25 hosts will answer correct? They won't all answer, just the one with the name that needs to be resolved. A lot of NetBIOS naming traffic is hosts announcing their own names actually. Nobody answers those. The issue isn't whether they answer or not anyway. Nor is it a bandwidth consumption issue, as you realize. It's an issue of eating CPU cycles on the hosts and NICs that receive the broadcast, which could be as many as 16,777,000 hosts with your current addressing scheme. Every NIC and host has to take in the packet, process it, and probably discard it, but still that could represent a significant amount of work. Your consultant is probably concerned that all devices are in the same broadcast domain. They all hear each other's broadcasts. If they are all announcing their names and trying to find each other by name and ARPing and RIPing and DHCPing, etc., this could become a performance issue on the hosts. Of course, you don't have nearly 16 million devices (25 you say?) so it's not an issue yet. Cisco recommends no more than 500 nodes per broadcast domain so you're pretty safe. The printers are going to broadcast at a particular rate regardless of the subnet mask. The packets they send probably aren't very big. They probably aren't using a lot of bandwidth But if you subdivided the network into multiple subnets and broadcast domains, using routers, not as many hosts will hear the broadcasts. The problem with broadcasts usually isn't a bandwidth consumption issue. It's a problem with the fact that a broadcast interrupts the CPU of every station in the broadcast domain. A lot of broadcasts can noticeably slow down an already slow computer with an old CPU. Nowadays, it would probably be a lot harder to cause a noticeable difference, CPUs are so fast. Anyway, your consultant may not be dumb, but she or he didn't describe the issue very well. Broadcast domains are covered in CCNA material, by the way. This isn't CCIE stuff. :-) Priscilla NetBSo how will a class A subnet mask cause this? Thanks for all input, please feel free to ramble, Steve Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=75219t=75213 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
