Oct 11, 2015 ~ Network Services

Design Hotspot-51 Server Mikrotik Download: Click here Mr.Mohamed Sam...

Quoting one of e-books and websites Identify the appropriate media, cables, ports, and connectors to connect Cisco network devices to other network devices and hosts in a LAN Select the appropriate media, cables, ports, and connectors to connect switches to other network devices...

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Quoting one of e-books and websites Predict the data flow between two hosts across a network Determine the path between two hosts across a network Once you create an internetwork by connecting your WANs and LANs to a router, you’ll need to configure logical network addresses,...

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Design Hotspot-51 Server Mikrotik

Download: Click here

Mr.Mohamed Samir

Quoting one of e-books and websites

Identify the appropriate media, cables, ports, and connectors to connect Cisco network devices to other network devices and hosts in a LAN

Select the appropriate media, cables, ports, and connectors to connect switches to other network devices and hosts
Ethernet cabling is an important discussion, especially if you are planning on taking the Cisco exams. Three types of Ethernet cables are available:
• Straight-through cable
• Crossover cable

• Rolled cable

Straight-Through Cable
The straight-through cable is used to connect

• Host to switch or hub
• Router to switch or hub

Four wires are used in straight-through cable to connect Ethernet devices. It is relatively simple to create this type; Figure 1.12 shows the four wires used in a straight-through Ethernet cable.

Notice that only pins 1, 2, 3, and 6 are used. Just connect 1 to 1, 2 to 2, 3 to 3, and 6 to 6, and you’ll be up and networking in no time. However, remember that this would be an Ethernet-only cable and wouldn’t work with voice, Token Ring, ISDN, and so on.

Crossover Cable

The crossover cable can be used to connect

• Switch to switch

• Hub to hub

• Host to host

• Hub to switch

• Router direct to host

The same four wires are used in this cable as in the straight-through cable; we just connect different pins together. Figure 1.13 shows how the four wires are used in a crossover Ethernet cable.

Notice that instead of connecting 1 to 1, 2 to 2, and so on, here we connect pins 1 to 3 and 2 to 6 on each side of the cable.

Rolled Cable

Although rolled cable isn’t used to connect any Ethernet connections, you can use a rolled Ethernet cable to connect a host to a router console serial communication (com) port.

If you have a Cisco router or switch, you would use this cable to connect your PC running HyperTerminal to the Cisco hardware. Eight wires are used in this cable to connect serial devices, although not all eight are used to send information, just as in Ethernet networking. Figure 1.14 shows the eight wires used in a rolled cable.

These are probably the easiest cables to make because you just cut the end off on one side of a straight-through cable, turn it over, and put it back on (with a new connector, of course).

Once you have the correct cable connected from your PC to the Cisco router or switch, you can start HyperTerminal to create a console connection and configure the device. Set the configuration as follows:

1. Open HyperTerminal and enter a name for the connection. It is irrelevant what you name it, but I always just use Cisco. Then click OK.

2. Choose the communications port—either COM1 or COM2, whichever is open on your PC.

3. Now set the port settings. The default values (2400bps and no flow control hardware) will
not work; you must set the port settings as shown in Figure 1.14.

FIGURE 1.14 Port settings for a rolled cable connection

Notice that the bit rate is now set to 9600 and the flow control is set to None. At this point, you can click OK and press the Enter key and you should be connected to your Cisco device console port.
We’ve taken a look at the various RJ45 unshielded twisted pair (UTP) cables. Keeping this in mind, what cable is used between the switches in Figure 1.15?

In order for host A to ping host B, you need a crossover cable to connect the two switches.

But what types of cables are used in the network shown in Figure 1.16?

The trouble is, we have a console connection that uses a rolled cable. Plus, the connection from the router to the switch is a straight-through cable, as is true for the hosts to the switches. Keep in mind that if we had a serial connection (which we don’t); it would be a V.35 that we’d use to connect us to a WAN.

Ccna Certified Mr.Mohamed Samir

Quoting one of e-books and websites

Predict the data flow between two hosts across a network

Determine the path between two hosts across a network
Once you create an internetwork by connecting your WANs and LANs to a router, you’ll need to configure logical network addresses, such as IP addresses, to all hosts on the internetwork so that they can communicate across that internetwork.
The term routing is used for taking a packet from one device and sending it through the network to another device on a different network. Routers don’t really care about hosts—they only care about networks and the best path to each network. The logical network address of the destination host is used to get packets to a network through a routed network, and then the hardware address of the host is used to deliver the packet from a router to the correct destination host.
If your network has no routers, then it should be apparent that you are not routing. Routers route traffic to all the networks in your internetwork. To be able to route packets, a router must know, at a minimum, the following:

• Destination address
• Neighbor routers from which it can learn about remote networks
• Possible routes to all remote networks
• The best route to each remote network
• How to maintain and verify routing information

The router learns about remote networks from neighbor routers or from an administrator. The router then builds a routing table (a map of the internetwork) that describes how to find the remote networks. If a network is directly connected, then the router already knows how to get to it.

If a network isn’t directly connected to the router, the router must use one of two ways to learn how to get to the remote network: static routing, meaning that someone must hand-type all network locations into the routing table, or something called dynamic routing. In dynamic routing, a protocol on one router communicates with the same protocol running on neighbor routers. The routers then update each other about all the networks they know about and place this information into the routing table. If a change occurs in the network, the dynamic routing protocols automatically inform all routers about the event. If static routing is used, the administrator is responsible for updating all changes by hand into all routers. Typically, in a large network, a combination of both dynamic and static routing is used.

Figure 1.10 shows a simple two-router network. Lab_A has one serial interface and three
LAN interfaces.

Looking at Figure 1.10, can you see which interface Lab_A will use to forward an IP datagram to a host with an IP address of 10.10.10.10?
FIGURE

By using the command show ip route, we can see the routing table (map of the internetwork) that Lab_A uses to make forwarding decisions:

Lab_A#sh ip route
[output cut]
Gateway of last resort is not set
C 10.10.10.0/24 is directly connected, FastEthernet0/0
C 10.10.20.0/24 is directly connected, FastEthernet0/1
C 10.10.30.0/24 is directly connected, FastEthernet0/2
C 10.10.40.0/24 is directly connected, Serial 0/0

The C in the routing table output means that the networks listed are “directly connected,” and until we add a routing protocol—something like RIP, EIGRP, or the like—to the routers in our internetwork (or use static routes), we’ll have only directly connected networks in our routing table.

So let’s get back to the original question: By looking at the figure and the output of the routing table, can you tell what IP will do with a received packet that has a destination IP address of 10.10.10.10? The router will packet-switch the packet to interface FastEthernet 0/0, and this interface will frame the packet and then send it out on the network segment.

Because we can, let’s do another example: Based on the output of the next routing table, which interface will a packet with a destination address of 10.10.10.14 be forwarded from?

Lab_A#sh ip route
[output cut]
Gateway of last resort is not set
C 10.10.10.16/28 is directly connected, FastEthernet0/0
C 10.10.10.8/29 is directly connected, FastEthernet0/1
C 10.10.10.4/30 is directly connected, FastEthernet0/2
C 10.10.10.0/30 is directly connected, Serial 0/0

First, you can see that the network is sub-netted and each interface has a different mask. And I have to tell you—you just can’t answer this question if you can’t subnet! 10.10.10.14 would be a host in the 10.10.10.8/29 subnet connected to the FastEthernet0/1 interface.

Figure 1.11 shows a LAN connected to Router A, which is, in turn, connected via a WAN link to RouterB. RouterB has a LAN connected with an HTTP server attached.

The critical information you need to glean from this figure is exactly how IP routing will occur in this example. Okay—we’ll cheat a bit. I’ll give you the answer, but then you should go back over the figure and see if you can answer example 2 without looking at my answers.
1. The destination address of a frame, from HostA, will be the MAC address of the F0/0 interface of the RouterA router.
2. The destination address of a packet will be the IP address of the network interface card (NIC) of the HTTP server.

3. The destination port number in the segment header will have a value of 80.

That example was a pretty simple one, and it was also very to the point. One thing to remember is that if multiple hosts are communicating to the server using HTTP, they must all use a different source port number. That is how the server keeps the data separated at the Transport layer.

Let’s mix it up a little and add another internetworking device into the network and then see if you can find the answers. Figure 1.12 shows a network with only one router but two switches.

What you want to understand about the IP routing process here is what happens when HostA sends data to the HTTPS server:
1. The destination address of a frame, from HostA, will be the MAC address of the F0/0 interface of the RouterA router.
2. The destination address of a packet will be the IP address of the network interface card (NIC) of the HTTPS server.
3. The destination port number in the segment header will have a value of 443.

Notice that the switches weren’t used as either a default gateway or another destination.

That’s because switches have nothing to do with routing. I wonder how many of you chose the switch as the default gateway (destination) MAC address for HostA? If you did, don’t feel bad—just take another look with that fact in mind. It’s very important to remember that the destination MAC address will always be the router’s interface—if your packets are destined for outside the LAN, as they were in these last two examples.

Before we move into some of the more advanced aspects of IP routing, let’s discuss ICMP in more detail, as well as how ICMP is used in an internetwork. Take a look at the network shown in Figure 1.13. Ask yourself what will happen if the LAN interface of Lab_C goes down

Lab_C will use ICMP to inform Host A that Host B can’t be reached, and it will do this by sending an ICMP destination unreachable message. Lots of people think that the Lab_A router would be sending this message, but they would be wrong because the router that sends the message is the one with that interface that’s down is located.

Let’s look at another problem: Look at the output of a corporate router’s routing table:

Corp#sh ip route
[output cut]
R 192.168.215.0 [120/2] via 192.168.20.2, 00:00:23, Serial0/0
R 192.168.115.0 [120/1] via 192.168.20.2, 00:00:23, Serial0/0
R 192.168.30.0 [120/1] via 192.168.20.2, 00:00:23, Serial0/0
C 192.168.20.0 is directly connected, Serial0/0
C 192.168.214.0 is directly connected, FastEthernet0/0

What do we see here? If I were to tell you that the corporate router received an IP packet with a source IP address of 192.168.214.20 and a destination address of 192.168.22.3, what do you think the Corp router will do with this packet?

If you said, “The packet came in on the FastEthernet 0/0 interface, but since the routing table doesn’t show a route to network 192.168.22.0 (or a default route), the router will discard the packet and send an ICMP destination unreachable message back out interface FastEthernet 0/0,” you’re a genius! The reason it does this is because that’s the source LAN where the packet originated from.

Ccna Certified Mr.Mohamed Samir

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Identify the appropriate media, cables, ports, and connectors to connect Cisco network devices to other network devices and hosts in a LAN

Predict the data flow between two hosts across a network

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Identify the appropriate media, cables, ports, and connectors to connect Cisco network devices to other network devices and hosts in a LAN

Predict the data flow between two hosts across a network

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