Unicast address and Multicast address

datchcha

What are the difference? I am having a hard time grasping the concept - can someone use an example that helped them to remember these terms.

Thank you

Mishra

It is pretty easy to figure out. The "casts" are simply where the information is going.

Unicast is direction from one source to another. Like server-client communication. When you view a file on a file server, you create a unicast connection to the file server to get the file and view it on your desktop.

Multicast is sending the exact same information from one source to multiple sources. Multicast is used in Symantec Ghost where you setup 9 clients to download the exact same image from a server so you don't have to do it 9 different times using unicast.

Broadcast is when you send the exact same informatiom from one source to ALL sources.

http://en.wikipedia.org/wiki/Unicast

dtlokee

To use an analogy to phones:

Unicast - one to one, you dialed somone's phone number and only one person answered.

Multicast - A conference call - only people who have joined the conference call are listening

Broadcast - PA system - everyone hears the message even if it isn't for them so they ignore it.

All TCP connections are unicast, they must be. UDP connections can be unicast, multicast, or broadcast depending on what the use is. Many streaming media type applications (listening to the radio on the Internet or video on demand) use multicast. Broadcasting is limited to the local subnet (or broadcast domain) only and won't be forwarded beyond the first router. Each subnet has a "broadcast" address that was intended to be used as a routable broadcast to a remote subet, but due to security implications it is rarely used.

datchcha

Wow...great help...thanks


Cheers.

datchcha

How do you tell which address is a Unicast and Mulitcast IP address?

Mishra

# What is a unicast IP address?
A unicast IP address is an IP address uniquely identifying a host in a network. The datagram with a unicast IP address is received and processed by only a single host. For example, the IP address 192.9.205.21 is a unicast IP address.

# What is a multicast IP address?
A multicast address is an IP address identifying a particular group of hosts in network. This group of hosts is called a multicast group. For example, the IP address 225.2.100.1 is a multicast IP address.

# What is a broadcast IP address?
The datagram with a broadcast IP address is received and processed by all the hosts in the local network. For example, the IP addresses 255.255.255.255, 192.9.205.255, 180.10.255.255, 10.255.255.255 are broadcast IP addresses.

Mishra

Multicast

224.0.0.0


224.0.0.255


Reserved for special “well-known” multicast addresses.

224.0.1.0


238.255.255.255


Globally-scoped (Internet-wide) multicast addresses.

239.0.0.0


239.255.255.255


Administratively-scoped (local) multicast addresses.

http://www.tcpipguide.com/free/t_IPMulticastAddressing.htm




By the way, I don't memorize the multicast IP address ranges... I usually know when I see one because of the numbers.

Netstudent

Also be aware of the multicast adresses for routing protocols.

Like RIpv2 routers listen on 224.0.0.9

Ospf DR's listen on 224.0.0.6
ospf nonDR's listen on 224.0.0.5

EIGRP listens on 224.0.0.10

These are used for multiaccess and broadcast environments like ethernet and frame-relay.

datchcha

Mishra wrote:

# What is a unicast IP address?
A unicast IP address is an IP address uniquely identifying a host in a network. The datagram with a unicast IP address is received and processed by only a single host. For example, the IP address 192.9.205.21 is a unicast IP address.

# What is a multicast IP address?
A multicast address is an IP address identifying a particular group of hosts in network. This group of hosts is called a multicast group. For example, the IP address 225.2.100.1 is a multicast IP address.

# What is a broadcast IP address?
The datagram with a broadcast IP address is received and processed by all the hosts in the local network. For example, the IP addresses 255.255.255.255, 192.9.205.255, 180.10.255.255, 10.255.255.255 are broadcast IP addresses.

What makes 192.9.205.21 a Unicast IP address?

Mishra

datchcha wrote:

Mishra wrote:

# What is a unicast IP address?
A unicast IP address is an IP address uniquely identifying a host in a network. The datagram with a unicast IP address is received and processed by only a single host. For example, the IP address 192.9.205.21 is a unicast IP address.

# What is a multicast IP address?
A multicast address is an IP address identifying a particular group of hosts in network. This group of hosts is called a multicast group. For example, the IP address 225.2.100.1 is a multicast IP address.

# What is a broadcast IP address?
The datagram with a broadcast IP address is received and processed by all the hosts in the local network. For example, the IP addresses 255.255.255.255, 192.9.205.255, 180.10.255.255, 10.255.255.255 are broadcast IP addresses.

What makes 192.9.205.21 a Unicast IP address?

Because it is an address that uniquely identifies a host. Just like any IP address on a workstation/server.

datchcha

Mishra wrote:

datchcha wrote:

Mishra wrote:

# What is a unicast IP address?
A unicast IP address is an IP address uniquely identifying a host in a network. The datagram with a unicast IP address is received and processed by only a single host. For example, the IP address 192.9.205.21 is a unicast IP address.

# What is a multicast IP address?
A multicast address is an IP address identifying a particular group of hosts in network. This group of hosts is called a multicast group. For example, the IP address 225.2.100.1 is a multicast IP address.

# What is a broadcast IP address?
The datagram with a broadcast IP address is received and processed by all the hosts in the local network. For example, the IP addresses 255.255.255.255, 192.9.205.255, 180.10.255.255, 10.255.255.255 are broadcast IP addresses.

What makes 192.9.205.21 a Unicast IP address?

Because it is an address that uniquely identifies a host. Just like any IP address on a workstation/server.

I thank all of you for your help, but i am not getting it. For example:

my network is 10.0.0.0 which give me 254 host, what would a unicat address appear as?

I currently have the Cisco Press Intro Book with me, but their models and examples are not showing what i need to see. Todd's Ed 4 is at home, so will be hitting that up later tonight.

Netstudent

Class D adresses are Multicast adresses. Everything else is unicast. The only way 10.0.0.0 would give you 254 hosts is with a subnet mask of 255.255.255.0. Having said that, all addresses in the range of 10.0.0.1-10.0.0.254 are unicast addresses because each address represents a single host. That is a class A address. Class D multicast addresses start with 224.

You probably need to read from several different sources to fully get it. Also read about IGMP which is Internet group management protocol. This defines the dynamic creation and membership of muticasting groups. It is an extension of the IP protocol.

Mishra

datchcha wrote:

Mishra wrote:

datchcha wrote:

Mishra wrote:

# What is a unicast IP address?
A unicast IP address is an IP address uniquely identifying a host in a network. The datagram with a unicast IP address is received and processed by only a single host. For example, the IP address 192.9.205.21 is a unicast IP address.

# What is a multicast IP address?
A multicast address is an IP address identifying a particular group of hosts in network. This group of hosts is called a multicast group. For example, the IP address 225.2.100.1 is a multicast IP address.

# What is a broadcast IP address?
The datagram with a broadcast IP address is received and processed by all the hosts in the local network. For example, the IP addresses 255.255.255.255, 192.9.205.255, 180.10.255.255, 10.255.255.255 are broadcast IP addresses.

What makes 192.9.205.21 a Unicast IP address?

Because it is an address that uniquely identifies a host. Just like any IP address on a workstation/server.

I thank all of you for your help, but i am not getting it. For example:

my network is 10.0.0.0 which give me 254 host, what would a unicat address appear as?

I currently have the Cisco Press Intro Book with me, but their models and examples are not showing what i need to see. Todd's Ed 4 is at home, so will be hitting that up later tonight.

Any piece of equipment that has an IP in your 10.0.0.0/24 range has its own unique unicast address. Unicast = IP address for the most part.

dtlokee

Any class A, B, or C address is considered unicast. Now on each subnet there will be a "subnet broadcast" address but if you don't know the subnet mask (as a transit router does not) it will forward these "subnet broadcast" packets as unicast. Class D addresses are Multicast addresses and will only be used for a destination address, never a source address.