sundance-communications.com/forum Forums TDM Business Telephone Systems Avaya - Lucent Telephones & Systems IP500 6.0 DHCP

I can answer that. When I hooked my Wireshark up and watched the traffic I can tell you that those VOIP phones are very busy little creatures. They are in a constant "conversation" with the base unit. You can see this also from the monitor application. From a network admin point of view you want to wall off that traffic as much as you can. We installed 72 phones and that uses up almost 1/3rd of the available IP addresses. If it's just a small LAN and a few phones it is no issue. When you have 100* computers and 72 phones it becomes an issue.

I thought we were discussing one physical network being shared by the phones and computers. The subnets are logical divisions of the local area network, not physically separate networks.

In a switched network each drop is a separate segment of the LAN. A typical IP phone codec uses about 50 kbs on a segment with a capacity of 100,000 kbs, or about one twentieth of one percent (0.050%).

Just using separate subnets or vlans does not reduce the traffic on a converged network.

Yes it does in a layer 2 environment. It is segmentation - analogous to bridging. Traffic only crosses segments as needed so for example subnet A does not get flooded with broadcasts etc from subnet B. They are in effect two discrete networks in this example, but capable of being bridged or routed. Isolating traffic is always the aim of any network design that one expects to scale upwards.

Okay now you lost me. When you are using two different ranges of addresses (2 different subnets) on one cable, that cable still has the same capacity. It is like sending blue balls and red balls down a pipe instead of just blue balls. How does that increase the capacity?

The switch in effect bridges the traffic so you do not see traffic on one side that was meant for the other. The Layer 2 acts like a very high speed brdging router. The cable is not the issue here. What is the issue is the speed of the switch. Switches are limited in the packets per second they can process. When you exceed their ability you have saturation. For this reason you run a switch off of a switch in a typical topology. Let's say you have a 24 port Layer 2 switch set up as VLAN a 10.1.1.0/24. You establish one or more ports as VLAN A for example subnet 10.1.2.0/24. Then you connect another switch, does not have to be VLAN but needs to be if you will route between them, to that port(2) Now you have isolated segments each with one subnet which you can route or switch between but the real value is you are keeping your traffic isolated to its own subnet thus reducing the load on the other switch. Depending on how you program them and their capabilities you can create all kinds of things from static routes to relays. It gives you far greater controil and reduces the loads on switches. The whole funtion of subnets is that you can break down your network into units and use appropriate hardware to communicate between them as desired. Otherwise all you have is one giant flat network which will underperform as it scales up.

Does that make sense to anyone else here? To me it makes no sense. To me 100 megabits per second means 100 megabits per second. It does not matter what IP address you put in a packet; it will still have the same number of bits. All that jargon and gobledygook doesn't change it.

Anyway as alluded to earlier, VOIP really uses very little network capacity on a fast ethernet network: about one twentieth of one percent.

The problem I have with VOIP over the converged LAN is that you are sharing the wires with those computer guys, and they generally don't give a fig, or even take delight, in seeing your phone system not work. I have seen it happen where just one infected desktop computer is flooding the whole LAN and preventing all other computers in the office from using the network or internet. Somehow the VOIP phones were still working, probably because they use very little bandwidth. But the customer calls in their serbo-croation speaking computer guy who says the problem must be that darned VOIP phone system that is using HIS network. I unplugged just one computer, through a process of elimination, and the problem went away. Problem is that I was in there 6 or 7 hours isolating the problem and the customer didn't want to pay. After all he is a Croat too, so who is he going to beleive?

One thing to consider, Butch is if you share a LAN with the Croation speaking goblededoodniks and the net is slammed by a DOS attack or some rogue app your phones go down with the rest of the net. In my example only the infected segment is down, the VOIP stays safe and secure. And working. Your confusion is you conflate speed with bandwidth. 100MbS is a transmission speed but you cannot maintain that *rate* as you ramp up if you do not have hardware that can handle the *volume* of traffic *at that speed*

I think what you are talking about is having a separate wiring plant just for the phones. Of coure that is better.

The original poster asked:
1) What options does the DHCP server have to hand out to the phones?

I don't think anyone has answered this question yet. Options are things like subnet, default gateway, time server, DNS server, etc. I think the DHCP server in the IPOffice 500 will handle this automatically. If it doesn't, it is beyond the scope of what we can tell you here on this board, and you need to get a networking professional.

2) Is it better to use the existing DHCP server?

I think what you are talking about is having a separate wiring plant just for the phones. Of coure that is better. But it would be very unusual. Most implementations of VOIP are going to share an existing network with the computers.

The original poster asked:
1) What options does the DHCP server have to hand out to the phones?

I don't think anyone has answered this question yet. Options are things like subnet, default gateway, time server, DNS server, etc. I think the DHCP server in the IPOffice 500 will handle this automatically. If it doesn't, it is beyond the scope of what we can tell you here on this board, and you need to get a networking professional,

2) Is it better to use the existing DHCP server?

I think this was already answered. It is better to use the DHCP server that comes in the IPOffice 500.

It is better to use a separate subnet for the phones so they won't use an IP address that may be in use by a computer. It makes the installation much easier.