cs610 solution
Leased line connections are mostly used in our homes and offices. Give a real time
example of leased lines.
A leased line is a service contract between a provider and a customer, whereby the
provider agrees to deliver a symmetric telecommunications line connecting two or
more locations in exchange for a monthly rent (hence the term lease). It is
sometimes known as a 'Private Circuit' or 'Data Line' in the UK or as CDN (Circuito
Diretto Numerico) in Italy. Unlike traditional PSTN lines it does not have a telephone
number, each side of the line being permanently connected to the other. Leased lines
can be used for telephone, data or Internet services.
An internet leased line is a premium internet connectivity product, delivered over
fiber normally, which is dedicated and provides uncontended, symmetrical speeds,
Full Duplex. It is also known as an ethernet leased line, DIA line, data circuit or
private circuit.
For example, a T-1 channel can be leased, and provides a maximum transmission
speed of 1.544 Mbit/s. The user can divide the connection into different lines for
multiplexing data and voice communication, or use the channel for one high speed
data circuit. Increasingly, leased lines are being used by companies, and even
individuals, for Internet access because they afford faster data transfer rates and are
cost-effective for heavy users of the Internet.
Advantages / benefits of leased lines
Leased lines have a number of advantages:
- Secure and private - dedicated exclusively to the customer
- Speed – symmetrical, uncontended and direct
- Reliable – private circuit local loops are a premium product supported by fast time
to fix guarantees
- Resilience – redundancy and separacy can be incorporated to reduce outages
- Wide choice of speeds – bandwidth on demand, easily upgradeable
- Dependable - leased lines are suitable for in-house office web hosting
Q2. How default routes are important in routing? In which type of network design
default routes are more appropriate to implement. Support your answer with routing
examples.
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.
But first, a little review...Remember that an internetwork is defined as two or more
networks connected with a router or routers. Also recall that routers don't keep track
of, or care even the slightest bit about, hosts, but they are extremely concerned
about networks and the best path to access each one.
Logical addressing (IP, for example) is what's used to identify each host on the
internetwork. Routers read the network portion of an IP address to figure out where
in the Net world a host is and then use a routing table to determine the best path to
the network that the destination host is located on.
Once that network is located, the packet is sent to the destination network by
forwarding the packet, hop-to-hop, until it reaches the specific router that's directly
connected to the destination host's network. From there, the destination host's
unique hardware address is used to get the packet to the host that's supposed to
receive it.
It's all about maps
Routers have maps, or at least a form of them. They must have a map of the entire
internetwork to explain to them where each logical network is located, as well as to
guide their decision in choosing the quickest, most efficient way to get there. This
map is called a routing table, and each routed protocol you use has to have its own
map. For instance, if you're running IP, IPX, and AppleTalk on your network, each of
your routers will have three maps—one for each routing protocol—all describing the
same physical networks in a different way.
It's kind of a language barrier thing; the reason each protocol has separate routing
tables is because each protocol really is like a different language. Say you've built a
gated community, and in it, you have a street you named Cat Street. Everyone on
that block speaks English, and the street sign is in English. Then a Spanish family
moves in that doesn't speak any English, so you add a sign that reads Avenida Gato.
Next, a French family moves in—they don't speak English or Spanish—so you add Le
Chat to the sign. You now have three separate signs describing Cat Street in three
different ways.
Configuring default routing
Since we have an Internet connection off the 2500B serial 0 interface, we need to
add a default route to the routing table of the 2500B router. This is just like adding a
static route, except wildcards of all zeros (0s) are used instead of a network and
mask.
Here is an example of configuring the serial 1 interface on the 2500B router and then
setting up default route. The ISP provided an IP address of 200.43.89.65/30 for the
interface. Since /30 is a block size of 4, the valid hosts are 65 and 66. We can set
our next hop to 66 since we were given 65 for our router’s interface.
The default route command is broken down as follows:
• • ip route: The command used to add a static or default route
• • 0.0.0.0: The wildcard used to say “any” network not already in the routing table
• • 0.0.0.0: Wildcard mask to say “any” network mask
• • 200.43.89.66: Next hop gateway
If you don't know the next hop gateway for some reason, you can always create the
command like this:
ip route 0.0.0.0 0.0.0.0 s1
This will tell the router to send packets that aren't in the routing table out serial 1.
Also, notice that I used the ip classless command. This tells the route not to drop
packets that are destined for a network that's not in the routing table, but to use the
default route instead. If you don't use the ip classless command, packets like that
would be dropped before being sent to the default route. (ip classless is on by
default in IOS 12.x.)