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 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.
ANSWER SHARE BY BILAL HAIDER
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.)
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.)
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