Using ipconfig and ifconfig

The utilities known as ipconfig (in Windows) and ifconfig (in Unix/Linux/Mac) will display the current configuration of TCP/IP on a given workstation—including the current IP address, DNS configuration, Windows Internet Naming Service (WINS) configuration, and default gateway. In the following sections, I will show you how to use both.

Using the ipconfig Utility

With the new Mac, Windows 10, and Windows Server 2016 operating systems, you can now see the IPv6 configuration because IPv6 is enabled by default. The output of the ipconfig command provides the basic routed protocol information on your machine. From a DOS prompt, type ipconfig, and you’ll see something like this:

Wow, there sure are a lot of options in this output compared to the output for earlier versions of Windows! First, what’s up with all these interfaces showing? I only have two—one Ethernet and one wireless. You can see that my Ethernet adapter shows up first, and it has an IP address, a mask, and a default gateway plus an IPv6 address and a DNS suffix. The next configured interface is the wireless local area network (LAN) adapter, which has an IP address, a mask, a default gateway, an IPv6 address, and the IPv6 default gateway as well. This IPv6 default gateway address is simply my router advertising that it runs IPv6 and saying, “I am the way out of the local LAN!”

The next adapters are disconnected because they are logical interfaces and I’m not using them—my machine actually shows eight, but I cut the output because it provides no new information. They’re automatically inserted because IPv6 is installed and running on my machine, and these adapters allow me to run IPv6 over an IPv4-only network.

But just in case the ipconfig command doesn’t provide enough information for you, try the ipconfig /all command—talk about details. Here’s the beginning of that output:

As you can see, it’s more of the same—a whole lot more. The most important thing I want you to notice is that I’ve received the hardware information about each interface, including the Media Access Control (MAC) address. Also significant is that I can see the Dynamic Host Configuration Protocol (DHCP) lease times and DNS addresses now.

But why stop here? There are two more valuable options you need to use with the ipconfig command. They are /release and /renew.

When you change networks, you need to get the IP address of that subnet and/or virtual LAN (VLAN). Windows 10 works most of the time without doing anything, but sometimes I do have to renew the IP configuration when changing networks. But that’s easy—just type ipconfig /renew from a command prompt, and if you’re connected to a DHCP server that’s available, you’ll then magically receive an IP address.

Now, if it still doesn’t work, you’ll need to release and renew your TCP/IP settings. To release your current DHCP TCP/IP information, you must elevate your command prompt or you’ll get this warning:

C:Users lammle>ipconfig /release

The requested operation requires elevation.

C:Users lammle>

Should this happen to you, choose Start ➢ All Programs ➢ Accessories ➢ Command Prompt, right-click, and choose Run As Administrator. (Of course, you’ll have to enter your name and password to do this if you are using Windows 7 or 10. But we love Windows 7 and 10, right? Okay, maybe not always.) Figure 17.4 shows how I did this.

Once your command prompt has been duly elevated, you can use the ipconfig /release command and then the ipconfig /renew command to get new TCP/IP information for your host.

Using the ifconfig Utility

There is a utility in Linux/Unix/Mac that will give you information similar to what ipconfig shows. It’s called ifconfig (short for interface configuration). Although ipconfig and ifconfig show similar information, there are major differences between these two utilities. The ipconfig utility is mainly used to view the TCP/IP configuration for a computer. You can use ifconfig to do the same thing, but ifconfig can also be used to configure a protocol or a particular network interface.

The general syntax of the ifconfig command is as follows:

ifconfig interface [address [parameters]]

The interface parameter equals the Unix name of the interface, such as eth0. If the optional address parameter is specified, the ifconfig command sets the IP address for the interface to the address you’ve specified. When the ifconfig command is used by itself with no parameters, all configured interfaces will be reported on. But if only the interface name is specified, you’ll get output that looks like this:

# ifconfig eth0

eth0 Link encap 10Mbps Ethernet HWaddr 00:00:C0:90:B3:42

inetaddr 172.16.0.2 Bcast 172.16.0.255 Mask 255.255.255.0 UP

BROADCAST RUNNING MTU 1500 Metric 0

RX packets 3136 errors 217 dropped 7 overrun 26

TX packets 1752 errors 25 dropped 0 overrun 0

Looking at this, we can see that the eth0 interface is a 10 Mbps Ethernet interface. The interface’s MAC and IP address information is displayed in this output as well. And, although not shown in the output, the ifconfig tool can show you the DNS information configured on the host.

Using the iptables utility

The iptables firewall utility is built for the Linux operating system. It is a command-line utility that uses what are called chains to allow or disallow traffic. When traffic arrives, iptables looks for a rule that addresses that traffic type, and if none exists, it will enforce the default rule. There are three different chain types:

• Input: Controls behavior for incoming connections
• Forward: Used for incoming connections that aren’t being delivered locally (like a router would receive)
• Output: Used for outgoing connections

You can set the default action to accept, drop, or reject, with the difference between reject and drop being that reject sends an error message back to the source.

The Windows ARP Table

The ARP table in Windows includes a list of TCP/IP addresses and their associated physical (MAC) addresses. This table is cached in memory so that Windows doesn’t have to perform ARP lookups for frequently accessed TCP/IP addresses like those of servers and default gateways. Each entry contains an IP address and a MAC address plus a value for TTL that determines how long each entry will remain in the ARP table.

Remember that the ARP table contains two kinds of entries:

• Dynamic
• Static

Dynamic ARP table entries are created whenever the Windows TCP/IP stack performs an ARP lookup but the MAC address isn’t found in the ARP table. When the MAC address of the requested IP address is finally found, or resolved, that information is then added into the ARP table as a dynamic entry. Whenever a request to send a packet to the host is sent to the Data Link layer, the ARP cache is checked first before an ARP broadcast is sent out. Remember, the ARP request is broadcast on the local segment—it does not go through a router.

The ARP table is cleared of dynamic entries whose TTL has expired to ensure that the entries are current.

Static ARP table entries serve the same function as dynamic entries but are made manually using the arp utility.

Using the arp Utility

You now know that ARP is a protocol included in the TCP/IP suite. You also understand that ARP is used by IP to determine the MAC address of a device that exists on the same subnet as the requesting device. When a TCP/IP device needs to forward a packet to a device on the local subnet, it first looks in its own table, called an ARP cache or mac address lookup table, for an association between the known IP address of the destination device on the local subnet and that same device’s MAC address. The cache is called that because the contents are periodically weeded out.

If no association that includes the destination IP address can be found, the device will then send out an ARP broadcast that includes its own MAC and IP information as well as the IP address of the target device and a blank MAC address field. Filling in that blank is the object of the whole operation—it’s the unknown value that the source device is requesting to be returned to it in the form of an ARP reply. Windows includes a utility called arp that allows us to check out the operating system’s ARP cache. To view this, from a Windows DOS prompt, use the arp command like this:

C:Uses lammle>arp

Displays and modifies the IP-to-Physical address translation tables used

by address resolution protocol (ARP).

ARP -s inet_addr eth_addr [if_addr]

ARP -d inet_addr [if_addr]

ARP -a [inet_addr] [-N if_addr] [-v]

Table 17.2 describes the various options that you can use with the arp command.

Sheesh. Looking at that output really makes me wish we were all just running IPv6 because, as you already should know, IPv6 doesn’t need ARP as well as many other annoying features and protocols required when running IPv4.

Of note, the Windows arp utility is primarily useful for resolving duplicate IP addresses. For example, let’s say your workstation receives its IP address from a DHCP server but it accidentally receives the same address that some other workstation gets. And so, when you try to ping it, you get no response. Your workstation is basically confused—it’s trying to determine the MAC address, and it can’t because two machines are reporting that they have the same IP address. To solve this little snag, you can use the arp utility to view your local ARP table and see which TCP/IP address is resolved to which MAC address.

To display the entire current ARP table, use the arp command with the –a switch like so to show you the mac address lookup table:

By the way, the –g switch will produce the same result.

Now, from this output, you can tell which MAC address is assigned to which IP address. Then, for static assignments, you can tell which workstation has a specific IP address and if it’s indeed supposed to have that address by examining your network documentation—you do have that record, right?

For DHCP-assigned addresses, you can begin to uncover problems stemming from multiple DHCP scopes or servers doling out identical addresses and other common configuration issues. And remember that under normal circumstances, you shouldn’t see IP addresses in the ARP table that isn’t a member of the same IP subnet as the interface.

If the machine has more than one network card (as may happen in Windows servers and on laptops with both Ethernet and wireless cards), each interface will be listed separately.

It’s good to know that in addition to displaying the ARP table, you can use the arp utility to manipulate the table itself. To add static entries to the ARP table, you use the arp command with the –s switch. These static entries will stay in the ARP table until the machine is rebooted. A static entry essentially hardwires a specific IP address to a specific MAC address so that when a packet needs to be sent to that IP address, it will automatically be sent to that MAC address. Here’s the syntax:

arp –s [IP Address] [MAC Address]

Simply replace the [IP Address] and [MAC Address] sections with the appropriate entries, like so:

arp –s 204.153.163.5 00–a0–c0–ab–c3–11

Now, take a look at your new ARP table by using the arp –a command. You should see something like this:

Finally, if you want to delete entries from the ARP table, you can either wait until the dynamic entries time out or use the –d switch with the IP address of the static entry you’d like to delete, like this:

arp –d 204.153.163.5

Doing so effectively deletes the entry from the ARP table in memory.

The arp utility doesn’t confirm successful additions or deletions (use arp -a or arp -g for that), but it will give you an error message if you use incorrect syntax.

Using the Nmap Utility

Nmap is one of the most popular port scanning tools used today. After performing scans with certain flags set in the scan packets, security analysts (and hackers) can make certain assumptions based on the responses received. These flags are used to control the TCP connection process and so are present only in TCP packets. Figure 17.5 show a TCP header with the important flags circled. Normally flags are “turned on” because of the normal TCP process, but hackers can craft packets to check the flags they wants to check.

Figure 17.5 shows these flags, among others:

• URG: Urgent pointer field significant
• ACK: Acknowledgment field significant
• PSH: Push function
• RST: Reset the connection
• SYN: Synchronize sequence numbers
• FIN: No more data from sender

While application of a scan and interpretation of the responses are beyond the scope of this book, security analysts and hackers alike can perform scans with these flags set in the scan packets to get responses that allow them to determine the following information:

• If a port is open on a device
• If the port is blocked by a firewall before its gets to the device

Nmap can also be used as follows:

• To determine the live hosts on a network
• To create a logical “map” of the network

Using the route Command Options

Let’s start with the switches you can use:

-f Using this command with any of the options like add, change, or delete will clear the routing table of all entries that aren’t host routes (routes with the subnet mask 255.255.255.255), the loopback network route or routes (routes with a destination of 127.0.0.0 and the subnet mask 255.0.0.0), and any multicast routes (those with a destination of 224.0.0.0 and the subnet mask 240.0.0.0).

-p If you use this with the add command, the individual route will be added to the Registry and then used to initialize the IP routing table whenever TCP/IP is started. Important to remember is that by default, the routes you’ve statically added won’t remain in the routing table the next time TCP/IP boots. And if you use -p with the print command, you’ll get shown a list of the persistent routes that are stored in the Registry location of HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParametersPersistentRoutes.

Now, let’s take a look at how and when you would use the route command. Table 17.4 shows the command options available and what they do when you are using the route command with them.

Here’s a description of some other tasks you can accomplish via the rest of the command’s options:

Destination This will give you the network destination of a given route. If the host bits of the network address are set to 0, it will be depicted with the destination’s IP network address, an IP address for a specific host route, or the default route of 0.0.0.0.

mask netmask This will provide you with the netmask—often referred to as the subnet mask—that’s associated with the destination network. The default destination subnet mask is 0.0.0.0, and typically you’ll see 255.255.255.255 representing a host route. It’s really important to remember that the destination address can’t be more specific than its corresponding subnet mask. What I’m saying is that there absolutely can’t be a bit set to 1 in the destination address if the equivalent bit in the subnet mask is a 0.

Gateway The gateway also depends on the network address and subnet mask, but it’s even more specific and delimits what’s called the next-hop IP address. For routes located on a local subnet, the gateway address maps directly to a particular interface. If the destination is on a remote network, the gateway IP address will direct packets to the neighboring router.

metric metric Metric refers to the cost of a given route from the sending to the receiving device, and it’s a value between 1 and 9999. Devices use this value to choose the best, or most efficient, routes among those in its routing table—the route with the lowest value wins. This decision can also include factors like the number of hops and the speed, reliability, and available bandwidth of the path being considered plus the various administrative aspects associated with it.

if interface This tool depends on information from the gateway address and determines the interface index for the specific interface that needs to receive the data. You can get a list of interfaces along with their relevant interface indexes by typing the route print command.

/? Using this will allow you to view help at the command prompt.

Some Examples of the route Command

Even though the finer points of the route command demand that you use caution when deploying some of the options, I’ll still list the basics of the route command because it can be really useful. I highly recommend that you spend some time practicing them on a non-production server, though—especially at first.

• To display the entire IP routing table, type route print.
• To add a default route with the default gateway address 192.168.10.1, type route add 0.0.0.0 mask 0.0.0.0 192.168.10.1.
• To add a route to the destination 10.1.1.0 with the subnet mask 255.255.255.0 and the next-hop address 10.2.2.2, type route add 10.1.1.0 mask 255.255.255.0 10.2.2.2.
• If you want to, let’s say, add a persistent route to the destination 10.100.0.0 with the subnet mask 255.255.0.0 and the next-hop address 10.2.0.1, type route -p add 10.100.0.0 mask 255.255.0.0 10.2.0.1. If you want to delete the route to the destination 10.100.0.0 with the subnet mask 255.255.0.0, enter route delete 10.100.0.0 mask 255.255.0.0.
• And finally, if you want to change the next-hop address of a route with the destination 10.100.0.0 and the subnet mask 255.255.0.0 from 10.2.0.1 to 10.7.0.5, type route change 10.100.0.0 mask 255.255.0.0 10.7.0.5.

Let’s move on to some other important Windows utilities.

The –a Switch

Making use of the –a switch will get you a remote machine’s NetBIOS name table consisting of a list of every NetBIOS name the machine from which you’ve deployed the switch knows of. The –a switch produced the output from server S1 shown in Figure 17.7.

So, using this switch arranges the NetBIOS name-table information in table form with output in four columns. The Name column displays the NetBIOS name entry for the remote host machine.

The next column gives you a unique two-digit hexadecimal identifier for the NetBIOS name. This identifier represents the last byte of the NetBIOS name depicted in the Name column, and it’s important because the same name could actually be used several times for the same machine. Plus, it identifies the specific service on the particular host that the name is referencing. Table 17.5 and Table 17.6 list the hexadecimal identifiers for unique and group hostnames.

The Type column refers to (surprise) the type of NetBIOS name being referenced. Unique NetBIOS names refer to individual hosts, and group names refer to logical groupings of workstations—either domains or workgroups.

The Status column gives you information about the status of a host’s NetBIOS even if it hasn’t been registered with the rest of the network.

The –A Switch

The –A switch works just like the –a switch and will give you the same output, but the syntax of the command is different. Obviously, you use an uppercase A instead of a lowercase one, and you also have to include the host’s IP address instead of its NetBIOS name. To use it, type nbtstat followed by –A and finally the IP address of the specific host whose NetBIOS table you want to check out:

nbtstat –A 199.153.163.2

The –c Switch

Use the –c switch to display the local NetBIOS name cache on the workstation it’s running on. Figure 17.8 shows sample output of the nbtstat –c command.

Each entry in this display shows the NetBIOS name, the hex ID for the service that was accessed, the type of NetBIOS name (unique or group), the IP address that the name resolves to, and its life. The Life value shows how many seconds each entry will live in the cache. When this time expires, the entry will be deleted.

Sometimes, deploying nbtstat to display the cache will get you the response “No names in the cache” because all entries in the cache have expired. This is what happens if you don’t regularly access machines or services with NetBIOS names.

The –n Switch

The –n switch will give you the local NetBIOS name table on a Windows device. Figure 17.9 shows output that’s similar to the output of the –a switch except for one important thing: What you’re seeing is the NetBIOS name table for the machine you’re running the command on instead of that of another host. Check it out.

The –r Switch

This switch is probably the one you’ll use most often when you want to get a hold of NetBIOS over TCP/IP (NBT) statistics because it tells you exactly how many NetBIOS names have been resolved to TCP/IP addresses. Figure 17.10 shows sample output of the nbtstat –r command.

What you can see here is that the statistics are divided into two categories. First, there are the NetBIOS names resolution and registration statistics. This is how many names have been resolved or registered either by broadcasts on the local segment or via lookup from a WINS name server.

Next you have the NetBIOS unique and group names and their associated hex IDs that were resolved or registered. In Figure 17.10, you can see that there’s a distinct lack of information regarding names resolved by a name server. What this means is that the output is telling you that there’s no WINS server operating—instead, all NetBIOS names were resolved by broadcast only.

The –r switch comes in handy when you want to determine how a workstation is resolving NetBIOS names and whether WINS is configured correctly. If WINS isn’t configured correctly or it’s simply not being used, the numbers in the Resolved By Name Server and Registered By Name Server categories will always be zero.

The –R Switch

Unlike the –a and –A switches, -r and -R use the same letter but do not have anything in common.

Here’s an example. Let’s say you have a bad name in the NetBIOS name cache but the right name is in the LMHOSTS file instead. (The LMHOSTS file contains NetBIOS names of stations and their associated IP addresses.) Because the cache is consulted before the LMHOSTS file is, that bad address will remain in the cache until it expires.

This command is used when you want to purge the NetBIOS name table cache and reload the LMHOSTS file into memory. You do that using the nbtstat command with the –R switch, like so:

nbtstat –R

You can practice this nbtstat -R command on your host to purge the NBT remote cache table.

The –S Switch

Using the -S switch will display the NetBIOS sessions table that lists all NetBIOS sessions to and from the host from which you issued the command. The –S switch displays both workstation and server sessions but lists remote addresses by IP address only.

Figure 17.11 shows sample output of the nbtstat –S command.

Here you can see the NetBIOS name being displayed along with its hex ID and the status of each session. An entry in the In/Out column determines whether the connection has been initiated from the computer on which you’re running nbtstat (outbound) or whether another computer has initiated the connection (inbound). The numbers in the Input and Output columns indicate in bytes the amount of data transferred between the stations.

The –s Switch

As with the –A and –a switches, the lowercase –s switch is similar to its uppercase sibling. The nbtstat –s command produces the same output as nbtstat –S except that it will also attempt to resolve remote-host IP addresses into hostnames. Figure 17.12 shows sample output from the nbtstat –s command.

Note the similarities between Figure 17.11 and Figure 17.12.

As with the netstat command, with the nbtstat command you can place a number for an interval at the end to direct it to deploy once every so many seconds until you press Ctrl+C.

The –a Switch

When you use the –a switch, the netstat utility displays all TCP/IP connections and all UDP connections. Figure 17.13 shows sample output produced by the netstat –a command.

The last two entries in Figure 17.13 show that the protocol is UDP and give the source-port nicknames nbname and nbdatagram. These are the well-known port numbers of 137 and 138, respectively. These port numbers are commonly seen on networks that broadcast the NetBIOS name of a workstation on the TCP/IP network. You can tell that this is a broadcast because the destination address is listed as *:* (meaning “any address, any port”).

The State column in Figure 17.13 has no entry for the UDP rows because UDP is not a connection-oriented protocol and, therefore, has no connection state.

The most common use for the –a switch is to check the status of a TCP/IP connection that appears to be hung. You can determine if the connection is simply busy or is actually hung and no longer responding.

The –e Switch

The -e switch displays a summary of all the packets that have been sent over the Network Interface Card (NIC) as of that instant. The Received and Sent columns show packets coming in as well as being sent:

You can use the –e switch to display the following categories of statistics:

Bytes The number of bytes transmitted or received since the computer was turned on. This statistic is useful for finding out if data is actually being transmitted and received or if the network interface isn’t doing anything at all.

Unicast Packets The number of packets sent from or received at this computer. To register in one of these columns, the packet must be addressed directly from one computer to another and the computer’s address must be in either the source or destination address section of the packet.

Non-unicast Packets The number of packets that weren’t directly sent from one workstation to another. For example, a broadcast packet is a non-unicast packet. The number of non-unicast packets should be smaller than the number of unicast packets. If the number of non-unicast packets is as high as or higher than that of unicast packets, too many broadcast packets are being sent over your network. Definitely find the source of these packets and make any necessary adjustments to optimize performance.

Discards The number of packets that were discarded by the NIC during either transmission or reception because they weren’t assembled correctly.

Errors The number of errors that occurred during transmission or reception. (These numbers may indicate problems with the network card.)

Unknown Protocols The number of received packets that the Windows networking stack couldn’t interpret. This statistic only shows up in the Received column because if the computer sent them, they wouldn’t be unknown, right?

Unfortunately, statistics don’t mean much unless they can be colored with time information. For example, if the Errors row shows 71 errors, is that a problem? It might be if the computer has been on for only a few minutes. But 71 errors could be par for the course if the computer has been operating for several days. Unfortunately, the netstat utility doesn’t have a way of indicating how much time has elapsed for these statistics.

The –r Switch

You use the –r switch to display the current route table for a workstation so that you can see exactly how TCP/IP information is being routed. This will give you the same output as the route print command that we covered earlier in this chapter.

The –s Switch

Using the –s switch displays a variety of TCP, UDP, IP, and ICMP protocol statistics. But be warned—the output you’ll get is really long, which may or may not be okay for you. For this book, it’s way too long for me to insert. With that in mind, we can add another modifier called the -p switch.

The –p Switch

Like the –n switch, the –p switch is a modifier that’s usually used with the –s switch to specify which protocol statistics to list in the output (IP, TCP, UDP, or ICMP). For example, if you want to view only ICMP statistics, you use the –p switch like so:

netstat –s –p ICMP

The netstat utility then displays the ICMP statistics instead of the entire gamut of TCP/IP statistics that the –s switch will typically flood you with. For a different example, let’s use the -s and -p switches to retrieve some IPv6 information:

Nice! Gets right to the point. Now, let’s see the TCP connections my host has:

This kind of efficiency is exactly why it’s good to use the -p modifier with the -s switch.

Because the Network+ exam doesn’t cover them, we won’t go into detail about what all these statistics mean for most of these commands. You can probably figure out most of them—for instance, Packets Received. For more details, go to Microsoft’s support website at https://support .microsoft.com/en-us.

The –n Switch

The -n switch is a modifier for the other switches. When used with them, it reverses the natural tendency of netstat to use names instead of network addresses. In other words, when you use the –n switch, the output always displays network addresses instead of their associated network names. Following is output from the netstat command used with the netstat -n command. It’s showing the same information but with IP addresses instead of names:

Examples of Using tcpdump

Use this command to capture traffic on all interfaces:

# tcpdump -i any

Here is the command to capture traffic on a particular interface:

# tcpdump -i eth0

And to filter traffic by IP, whether it’s the source or the destination, use this command:

# tcpdump host 192.168.5.5

Starting FTP and Logging In to an FTP Server

Of the two FTP file operations (download and upload), the ability to download files is definitely the more crucial for you to have down as a network technician or sys admin. The reason it’s so important for you to master is that network and client operating system drivers and patches are located on FTP servers all over the Internet.

The first steps in starting an FTP download session are to determine the address of the FTP site and start the ftp utility. The FTP site typically has the same name as the website except that the first three characters are ftp instead of www. For example, Microsoft’s website is www.microsoft.com. Its FTP site, on the other hand, is ftp.microsoft.com. We’ll use my personal FTP site as an example for the rest of this section because it works, so I can actually log in to it.

First, start the ftp utility as demonstrated earlier, and then follow these steps:

1. At the ftp command prompt, type open, a space, and the name of the FTP server, like this:

   C:Users lammle>ftp

   ftp>open ftp.lammle.com

   Connected to ftp.lammle.com.

   220---------- Welcome to Pure-FTPd [TLS] ----------

   220-You are user number 1 of 50 allowed.

   220-Local time is now 11:45. Server port: 21.

   220-IPv6 connections are also welcome on this server.

   220 You will be disconnected after 15 minutes of inactivity.

   User (ftp.lammle.com:(none)):enter

   230 Anonymous user logged in

   ftp>

   As shown here, if the FTP server is available and running, you’ll receive a response welcoming you to the server and asking you for a username. Right now, I just have Anonymous as the username (enabled by default on the FTP server), which means that anyone can log in to it. (By the way, don’t bother trying this on my server because I disabled it for obvious reasons as soon as I finished writing this section.)

   You can also start an FTP session by typing ftp, a space, and the address of the FTP server (for example, ftp ftp.globalnettraining.com). This allows you to start the ftp utility and open a connection in one step. Here’s an example:

   C:Users lammle>ftp ftp.globalnettraining.com

   Connected to ftp.globalnettraining.com.

   220 Microsoft FTP Service

   User (ftp.globalnettraining.com:(none)):todd

   331 Password required for todd.

   Password:not shown when typed

   230 User todd logged in.

   ftp>quit

2. Enter a valid username, and press Enter.
3. Enter your password, and press Enter. (The password won’t show up when you type it.)

Most Internet web servers that allow just about anyone to download files also allow the username anonymous, as I demonstrated. In addition to anonymous, you can use the username ftp to gain access to a public FTP server. They are both anonymous usernames. Remember that FTP (and Unix) usernames are case sensitive.

All good, but if you want to access a private FTP server, as I’ll demonstrate in a minute, you’ll need to use the username and password given to you by the site’s administrator. Oh, and sometimes you can use your email address as a password when accessing a public FTP server with a username like anonymous.

You don’t have to enter your entire email address to log in with the anonymous username. Most of the time, FTP server software doesn’t actually verify the actual email address, only that it is, in fact, an email address. To do this, it checks for an @ sign and two words separated by a period. You just need to enter a very short email address to bypass the password (like [email protected]). This is especially helpful if you have a long email address, and it’s a really good idea if you don’t want to get a ton of junk email.

If you enter the wrong username and/or password, the server will tell you so by displaying the following and leaving you at the ftp command prompt:

530 Login Incorrect

Login failed.

This means you’ve got to try again and must start the login process over. If you’re successful, the FTP server will welcome you and drop you back at the ftp command prompt. You’re now ready to start uploading or downloading files.

Downloading Files

After you log in to the FTP server, you’ll navigate to the directory that contains the files you want. Thankfully, the FTP command-line interface is similar to the DOS command-line interface. This is no surprise because DOS is based on Unix and FTP is a Unix utility. Table 17.8 lists and describes the common navigation commands for FTP. (Remember that these are also case sensitive.)

After you navigate to the directory and find the file you want to download, it’s time to set the parameters for the type of file. Files come in two types:

• ASCII, which contains text
• Binary, which is all other files

If you set ftp to the wrong type, the file you download will contain gibberish. So if you’re in doubt, set ftp to download files as binary files. Check out Table 17.8.

To set the file type to ASCII, type ascii at the ftp command prompt. ftp will respond by telling you that the file type has been set to A (ASCII):

ftp>ascii

Type set to A

To set the file type to binary, type binary at the ftp command prompt. ftp will respond by telling you that the file type has been set to I (binary):

ftp>binary

Type set to I

To download the file, just use the get command like this:

ftp>get lammlepress.exe

200 PORT command successful.

150 Opening BINARY mode data connection for 'scrsav.exe'

(567018 bytes).

The file will start downloading to your hard drive. Unfortunately, with its default settings, the ftp utility doesn’t give you any indication of the progress of the transfer. When the file has downloaded, the ftp utility will display the following message and return you to the ftp command prompt:

226 Transfer complete.

567018 bytes received in 116.27 seconds (4.88 Kbytes/sec)

You can download multiple files by using the mget command. Simply type mget, a space, and then something known as a wildcard that specifies the files you want to get. For example, to download all the text files in a directory, type mget *.txt.

Uploading Files

To upload a file to an FTP server, you’ve got to have rights on that specific server. These rights are assigned on a directory-by-directory basis. To upload a file, log in and then follow these steps:

1. At the ftp command prompt, type lcd to navigate to the directory on the local machine where the file resides.
2. Type cd to navigate to the destination directory.
3. Set the file type to ASCII or binary.
4. Use the put command to upload the file.

The syntax of the put command looks like this:

ftp>put local file destination file

Let’s say you want to upload a file called 1.txt on the local server but you want it to be called my.txt on the destination server. To accomplish that, use the following command:

ftp>put 1.txt my.txt

You’ll get the following response:

200 PORT command successful.

150 Opening BINARY mode data connection for collwin.zip

226 Transfer complete.

743622 bytes sent in 0.55 seconds (1352.04 Kbytes/sec)

You can upload multiple files using the mput command. Simply type mput, a space, and then a wildcard that specifies the files. For example, to upload all the text files in a directory, type mput *.txt.

When you’re finished with the ftp utility, just type quit to return to the command prompt.

How to Enable Telnet in Windows

Because most people have the Windows 10 operating system running on their PCs these days, it’s good to know that, by default, these operating systems install without Telnet available. But there’s a way around that one—if you really must have a Telnet client enabled in these operating systems, here’s how to do it:

1. Open Control Panel.
2. Select Programs And Features.
3. In the left column, select Turn Windows Features On Or Off (get ready for the annoying User Account Control [UAC] prompt, and then enter your name and password).
4. Select the Telnet check box (and any other obscure services you may want enabled), and wait while Windows thinks for a while and then reboots.

Nice—now you can go to Start and then type telnet in the Start search box to get a Telnet window to open for you. You can also open a DOS prompt and just type telnet from there. Here are the options that Windows provides with Telnet:

Now that we’ve finished talking about Telnet, my personal recommendation is that you never use it again. What? Yes, you read that right, and here’s why.

Don’t Use Telnet, Use Secure Shell

What? I just told you how to use Telnet, and now I am telling you not to use it. That’s right, don’t use Telnet! Telnet is totally insecure because it sends all data in crystal-clear text—including your name and password. And I’m pretty sure you know that’s a really bad thing these days. If Microsoft doesn’t even enable it on its latest OSs, then you know it really must be insecure.

So if you shouldn’t use Telnet, what should you use instead? Secure Shell (SSH) is your answer. It provides the same options as Telnet, plus a lot more; but most important, it doesn’t send any data in clear text. The thing is, your servers, routers, and other devices need to be enabled with SSH, and it’s not configured by default on most devices.

Some configuration is usually necessary if you want things to work as they really should, and yes, sometimes it’s a little painful to get everything running smoothly, but it’s all worth it in the long run. Personally, I disable Telnet on all my routers and use SSH exclusively. No lie—I never use Telnet anymore if I can help it. Even so, you should still understand Telnet and get in some practice with it in case you do ever need it.

In my Sybex book Cisco CCNA Study Guide, I get into the skinny on how to configure SSH on all Cisco devices and use an SSH client.