Metrics is a property of a route in computer networking,
consisting of any value used by routing algorithms to
determine whether one route should perform better than
another. The routing table stores only the best possible
routes, while link-state or topological databases may store
all other information as well. For example, RIP uses
hopcount (number of hops) to determine the best possible route.

Metrics is represented by:

    * number of hops (hop count)
    * speed of the path
    * latency (delay)
    * path reliability
    * path bandwidth
    * load
    * MTU

In EIGRP, metrics is represented by an integer from 0 to
4294967295. In Microsoft Windows XP routing it ranges from 1
to 9999.

A default route, also known as the gateway of last resort,
is the network route used by a router when no other known
route exists for a given IP packet's destination address.
All the packets for destinations not known by the router's
routing table are sent to the default route. This route
generally leads to another router, which treats the packet
the same way: If the route is known, the packet will get
forwarded to the known route. If not, the packet is
forwarded to the default-route of that router which
generally leads to another router. And so on. Each router
traversal adds a one-hop distance to the route.

Once the router with a known route to an host destination is
reached, the router determines which route is valid by
finding the "most specific match". The network with the
longest subnet mask that matches the destination IP address
wins.

The default route in IPv4 (in CIDR notation) is 0.0.0.0/0,
often called the quad-zero route. Since the subnet mask
given is /0, it effectively specifies no network, and is the
"shortest" match possible. A route lookup that doesn't match
anything will naturally fall back onto this route.
Similarly, in IPv6 the default address is given by ::/0.

Routers in an organization generally point the default route
towards the router that has a connection to a network
service provider. This way, packets with destinations
outside of the organization's local area network
(LAN)?typically to the Internet, WAN, or VPN?will be
forwarded by the router with the connection to that provider.

Host devices in an organization generally refer to the
default route as a default gateway which can be, and usually
is, a filtration device such as a firewall or Proxy server.

A state in which a message that has been broadcast across a 
network results in even more responses, and each response 
results in still more responses in a snowball effect. A 
severe broadcast storm can block all other network traffic, 
resulting in a network meltdown. Broadcast storms can 
usually be prevented by carefully configuring a network to 
block illegal broadcast messages

The layer2 ,datalink layer is responsible for moving frames 
from one hop(node)to the next.Whereas in layer3 i,e network 
layer is responsible for the delivery of individual packets
from source host to destination host.

Basically a layer 2 switch operates utilizing Mac addresses 
in it's caching table to quickly pass information from port 
to port. A layer 3 switch utilizes IP addresses to do the 
same. 

While the previous explanation is the "What", for folks in 
networking the following "How" is far more interesting. 

Essentially, A layer 2 switch is essentially a multiport 
bridge. A layer 2 switch will learn about MAC addresses 
connected to each port and passes frames marked for those 
ports. It also knows that if a frame is sent out a port but 
is looking for the MAC address of the port it is connected 
to and drop that frame. Whereas a single CPU Bridge runs in 
serial, todays hardware based switches run in parallel, 
translating to extremly fast switching. 

Layer 3 switching is a hybrid, as one can imagine, of a 
router and a switch. There are different types of layer 3 
switching, route caching andtopology-based. In route 
caching the switch required both a Route Processor (RP) and 
a Switch Engine (SE). The RP must listen to the first 
packet to determine the destination. At that point the 
Switch Engine makes a shortcut entry in the caching table 
for the rest of the packets to follow. Due to advancement 
in processing power and drastic reductions in the cost of 
memory, today's higher end layer 3 switches implement a 
topology-based switching which builds a lookup table and 
and poputlates it with the entire network's topology. The 
database is held in hardware and is referenced there to 
maintain high throughput. It utilizes the longest address 
match as the layer 3 destination. 

Now when and why would one use a l2 vs l3 vs a router? 
Simply put, a router will generally sit at the gateway 
between a private and a public network. A router can 
perform NAT whereas an l3 switch cannot (imagine a switch 
that had the topology entries for the ENTIRE Internet!!). 
In a small very flat network (meaning only one private 
network range for the whole site) a L2 switch to connect 
all the servers and clients to the internet is probably 
going to suffice. Larger networks, or those with the need 
to contain broadcast traffic or those utilizing VOIP, a 
multi network approach utilizing VLANs is appropriate, and 
when one is utilizing VLANs, L3 switches are a natural fit. 
While a router on a stick scenario can work, it can quickly 
overtax a router if there is any significant intervlan 
traffic since the router must make complicated routing 
decisions for every packet that it recieves.

Yes, it is necessary to use cross-over cable to connect to 
same type of devices, and here EZ serial switch and hub are 
of the same type.

No, the EZ serial switch does not have a user configuration 
interface because there is no need for a user to configure 
an EZ serial switch to have a LAN/WAN based connection.  
All the changes should be applied under the Operating 
System itself.

Auto-negotiation is a mechanism that takes control of the 
cable when a connection is established to a network device. 
Auto-negotiation detects the various modes that exist in 
the device on the other end of the wire, and advertises it 
own abilities to automatically configure the highest 
performance mode of interoperation.
Auto-negotiation automatically switches to the correct 
technology, such as 10BASE-T, 100BASE-TX, or a 
corresponding Full Duplex mode. Once the highest 
performance common mode is determined, Auto-negotiation 
passes control of the cable to the appropriate technology 
and becomes transparent until the connection is broken.

The switch can obtain its IP configuration automatically 
using one of the following protocols: 

?Bootstrap Protocol (BOOTP) 

?Dynamic Host Configuration Protocol (DHCP) 

?Reverse Address Resolution Protocol (RARP) 

The switch makes BOOTP, DHCP, and RARP requests only if the 
sc0 interface IP address is set to 0.0.0.0 when the switch 
boots up. This address is the default for a new switch or a 
switch whose configuration file has been cleared using the 
clear config all command. BOOTP, DHCP, and RARP requests 
are only broadcast out the sc0 interface.

We can manually give the IP address to the switch there is 
no predfined IP address of the switch. The IP address is 
depends onto the network administrator

Yes it will work.Its least bothered of pc/os it may be any 
os.what it needs is MAC address of pcs.swithch is a 
inteligent device which keeps ur pcs in one network to 
communicate each other.

Yes, It can act like a DHCP.

A switch,  keeps a record of the MAC addresses of all the 
devices connected to it. With this information, a switch 
can identify which system is sitting on which port. So when 
a frame is received, it knows exactly which port to send it 
to, which significantly increases network response times. 
And, unlike a Hub, a 10/100Mbps switch will allocate a full 
10/100Mbps to each of its ports. So regardless of the 
number of PCs transmitting, users will always have access 
to the maximum amount of bandwidth. It's for these reasons 
why a switch is considered to be a much better choice then 
a hub. 

Routers are completely different creatures. Where a hub or 
switch is concerned with transmitting frames, a router's 
job, as its name implies, is to route packets to other 
networks until that packet ultimately reaches its 
destination. One of the key features of a packet is that it 
not only contains data, but the destination address of 
where it's going. 

A router is typically connected to at least two networks, 
commonly two LANs or WANs or a LAN and its ISP's network 
(ex. your pc or workgroup and EarthLink). Routers are 
located at gateways, the places where two or more networks 
connect. Using headers and forwarding tables, routers 
determine the best path for forwarding the packets. Routers 
use protocols such as ICMP to communicate with each other 
and configure the best route between any two hosts. 

A router will typically include a 4-to-8 port Ethernet 
switch (or hub) and a Network Address Translator (NAT). In 
addition, they usually include a Dynamic Host Configuration 
Protocol (DHCP) server, Domain Name Service (DNS) proxy 
server and a hardware firewall to protect the Local Area 
Network (LAN) from malicious intrusion from the Internet.

In a hub, a frame is passed along or "broadcast" to every 
one of its ports. It doesn't matter that the frame is only 
destined for one port. The hub has no way of distinguishing 
which port a frame should be sent to. Passing it along to 
every port ensures that it will reach its intended 
destination. This places a lot of traffic on the network 
and can lead to poor network response times. 

Additionally, a 10/100Mbps hub must share its bandwidth 
with each and every one of its ports. So when only one PC 
is broadcasting, it will have access to the maximum 
available bandwidth. If, however, multiple PCs are 
broadcasting, then that bandwidth will need to be divided 
between all of those systems, which will degrade 
performance. 

A switch, on the other hand, keeps a record of the MAC 
addresses of all the devices connected to it. With this 
information, a switch can identify which system is sitting 
on which port. So when a frame is received, it knows 
exactly which port to send it to, which significantly 
increases network response times. And, unlike a Hub, a 
10/100Mbps switch will allocate a full 10/100Mbps to each 
of its ports. So regardless of the number of PCs 
transmitting, users will always have access to the maximum 
amount of bandwidth. It's for these reasons

switch operates on data link layer.
hub operates on physical layer only.

GO for CISCO D link in ITS site

voip work on packet switching.analog data convert in 
discreat packets(codec used for this) & traval over 
internet.voice travel in digital form .

voip is an protocol where u can call a telephone over an
internet