1 00:00:00,090 --> 00:00:01,770 In this lesson, we're going to cover 2 00:00:01,770 --> 00:00:03,990 four more network device commands, 3 00:00:03,990 --> 00:00:08,580 including show MAC address table, ARP, VLAN, and power. 4 00:00:08,580 --> 00:00:09,510 Let's go ahead and take a look 5 00:00:09,510 --> 00:00:11,760 at the show MAC address table first. 6 00:00:11,760 --> 00:00:13,380 The show MAC address table command 7 00:00:13,380 --> 00:00:15,000 is going to display the MAC address table 8 00:00:15,000 --> 00:00:17,490 on a Cisco switch, and this will provide the mapping 9 00:00:17,490 --> 00:00:20,340 of the MAC addresses to their corresponding ports. 10 00:00:20,340 --> 00:00:22,620 The show MAC address table command can be used 11 00:00:22,620 --> 00:00:24,270 for troubleshooting to help you identify, 12 00:00:24,270 --> 00:00:27,030 which devices are connected on which ports. 13 00:00:27,030 --> 00:00:29,520 When you enter the show MAC address table command, 14 00:00:29,520 --> 00:00:30,810 you're going to get a table displayed 15 00:00:30,810 --> 00:00:32,369 to your screen that will usually include 16 00:00:32,369 --> 00:00:33,960 four basic columns. 17 00:00:33,960 --> 00:00:36,630 The first column will be a BID or VLAN, 18 00:00:36,630 --> 00:00:38,790 which will show the bridge ID or VLAN associated 19 00:00:38,790 --> 00:00:40,350 with that particular device. 20 00:00:40,350 --> 00:00:42,330 The second column will be the MAC address, 21 00:00:42,330 --> 00:00:43,830 which will be the MAC address of the device 22 00:00:43,830 --> 00:00:46,110 connected on that specific switch port. 23 00:00:46,110 --> 00:00:48,750 The third will be the type of connection, and usually, 24 00:00:48,750 --> 00:00:50,190 this is going to be dynamic because 25 00:00:50,190 --> 00:00:51,930 it's going to dynamically read the MAC address 26 00:00:51,930 --> 00:00:53,970 from the card reported by the device 27 00:00:53,970 --> 00:00:56,070 when it connects onto that switch port. 28 00:00:56,070 --> 00:00:58,170 And then the fourth column is going to be the port, 29 00:00:58,170 --> 00:00:59,340 and this will list out the port 30 00:00:59,340 --> 00:01:03,090 being used by the switch, such as FA0/18 31 00:01:03,090 --> 00:01:06,150 if it was on port 18 of your switch. 32 00:01:06,150 --> 00:01:07,530 Next, we're going to take a look 33 00:01:07,530 --> 00:01:09,420 at the show ARP command. 34 00:01:09,420 --> 00:01:11,640 Now the show ARP command is going to be used 35 00:01:11,640 --> 00:01:13,800 to display the ARP table, which is the address 36 00:01:13,800 --> 00:01:16,920 resolution table inside of that device. 37 00:01:16,920 --> 00:01:18,990 This will show you the mapping of IP addresses 38 00:01:18,990 --> 00:01:20,400 to MAC addresses. 39 00:01:20,400 --> 00:01:22,410 This is going to be used to verify the IP addresses 40 00:01:22,410 --> 00:01:23,580 are being correctly mapped to the 41 00:01:23,580 --> 00:01:25,140 MAC addresses on your network, 42 00:01:25,140 --> 00:01:26,760 and you can use this if you suspect 43 00:01:26,760 --> 00:01:28,290 that ARP cache poisoning 44 00:01:28,290 --> 00:01:30,630 or ARP spoofing is occurring on your network, 45 00:01:30,630 --> 00:01:32,370 and you need to validate that to make sure 46 00:01:32,370 --> 00:01:33,930 the right IP addresses are being mapped 47 00:01:33,930 --> 00:01:36,090 to the correct MAC addresses and the type 48 00:01:36,090 --> 00:01:37,920 of connection that's being used. 49 00:01:37,920 --> 00:01:40,560 When you type in the show ARP command and hit enter, 50 00:01:40,560 --> 00:01:41,850 you're going to get a small table 51 00:01:41,850 --> 00:01:42,780 that's going to show up, 52 00:01:42,780 --> 00:01:45,210 which is going to give you the protocol, the address, 53 00:01:45,210 --> 00:01:48,060 the age, the hardware address, the type, 54 00:01:48,060 --> 00:01:49,290 and the interface. 55 00:01:49,290 --> 00:01:51,360 In the first column, we have the protocol. 56 00:01:51,360 --> 00:01:52,380 When it says internet, 57 00:01:52,380 --> 00:01:55,980 this means that we are using the IP or internet protocol. 58 00:01:55,980 --> 00:01:57,690 Second, we have the address, 59 00:01:57,690 --> 00:01:59,850 and this is the layer three type of address, 60 00:01:59,850 --> 00:02:02,520 and usually it's going to be in a dotted decimal notation 61 00:02:02,520 --> 00:02:06,090 if you're using IP version 4, as you can see here. 62 00:02:06,090 --> 00:02:08,150 The next column you have is the age, 63 00:02:08,150 --> 00:02:09,479 and this will show you the minimum age 64 00:02:09,479 --> 00:02:11,220 for this MAC binding. 65 00:02:11,220 --> 00:02:14,730 If it shows a dash, this means there is no minimum age. 66 00:02:14,730 --> 00:02:16,980 The next column we have is the hardware address, 67 00:02:16,980 --> 00:02:18,930 and this is going to be written as three groups 68 00:02:18,930 --> 00:02:22,560 of four hexadecimal digits, each one separated by a dot. 69 00:02:22,560 --> 00:02:24,000 Normally, when you see a MAC address 70 00:02:24,000 --> 00:02:25,980 being written down as a hardware address, 71 00:02:25,980 --> 00:02:28,290 you'll see it written as 12 characters grouped 72 00:02:28,290 --> 00:02:30,630 into two hexadecimal characters each, 73 00:02:30,630 --> 00:02:33,720 and each one being separated by either a dash or a colon. 74 00:02:33,720 --> 00:02:35,640 But when you're using the show ARP command, 75 00:02:35,640 --> 00:02:38,490 you'll see it written as three groups of four hexadecimal 76 00:02:38,490 --> 00:02:41,040 characters each separated by dots. 77 00:02:41,040 --> 00:02:42,540 The next column we have is the type, 78 00:02:42,540 --> 00:02:44,670 and if you see here, it says ARPA, that means that 79 00:02:44,670 --> 00:02:47,760 this is an internet protocol version four type of binding 80 00:02:47,760 --> 00:02:50,040 because we're using the ARPANET notation, 81 00:02:50,040 --> 00:02:52,470 which was the original version of the internet. 82 00:02:52,470 --> 00:02:54,870 And this also says which switch port is being used 83 00:02:54,870 --> 00:02:56,460 for this particular binding, 84 00:02:56,460 --> 00:03:00,060 and in this case we can see it's ethernet 0/0. 85 00:03:00,060 --> 00:03:03,540 The third one we have is known as show VLAN. 86 00:03:03,540 --> 00:03:05,550 Now, the show VLAN command is going to be used 87 00:03:05,550 --> 00:03:08,640 to configure the VLAN settings on a given switch. 88 00:03:08,640 --> 00:03:10,050 Now, it's going to be utilized to segment 89 00:03:10,050 --> 00:03:11,880 your network traffic for improved performance 90 00:03:11,880 --> 00:03:13,530 and security by creating all 91 00:03:13,530 --> 00:03:15,030 of your different VLANs. 92 00:03:15,030 --> 00:03:16,770 When you type in the show VLAN, 93 00:03:16,770 --> 00:03:17,730 you're going to be able to display 94 00:03:17,730 --> 00:03:19,793 the VLAN mappings on your particular device, 95 00:03:19,793 --> 00:03:21,960 and this will be shown in a series 96 00:03:21,960 --> 00:03:23,910 of four columns as well. 97 00:03:23,910 --> 00:03:25,350 When you deal with the four columns, 98 00:03:25,350 --> 00:03:26,940 you're going to have the VLAN number, 99 00:03:26,940 --> 00:03:28,530 you're going to have the name of the VLAN, 100 00:03:28,530 --> 00:03:29,520 you're going to have the status, 101 00:03:29,520 --> 00:03:30,900 and you're going to have the ports. 102 00:03:30,900 --> 00:03:33,720 In the first column, you'll have the VLAN identifier, 103 00:03:33,720 --> 00:03:37,350 which in this case shows one and 10 as my two VLAN. 104 00:03:37,350 --> 00:03:39,420 Then you'll see the VLAN names. 105 00:03:39,420 --> 00:03:42,720 The first one, which is VLAN 1, is the default VLAN, 106 00:03:42,720 --> 00:03:43,890 and that is how it is always set up 107 00:03:43,890 --> 00:03:45,840 on a Cisco device by default, 108 00:03:45,840 --> 00:03:48,000 and I do recommend you change VLAN 1 109 00:03:48,000 --> 00:03:49,500 from being the default into 110 00:03:49,500 --> 00:03:51,270 being something else as your default, 111 00:03:51,270 --> 00:03:53,990 such as VLAN 100, or VLAN 123, 112 00:03:53,990 --> 00:03:55,200 or something like that. 113 00:03:55,200 --> 00:03:57,960 That's harder for an attacker or hacker to guess. 114 00:03:57,960 --> 00:03:59,610 Next, we have the status column, 115 00:03:59,610 --> 00:04:01,920 and this will tell us if the VLAN is active or not. 116 00:04:01,920 --> 00:04:04,320 And then we have the ports associated with that VLAN. 117 00:04:04,320 --> 00:04:06,060 And here you can see the default VLAN 118 00:04:06,060 --> 00:04:07,980 has four ports associated with it, 119 00:04:07,980 --> 00:04:10,083 which is FA0/1/2/3 and /4. 120 00:04:12,390 --> 00:04:14,730 And then we have VLAN 10, which is going to be 121 00:04:14,730 --> 00:04:18,029 our user VLAN, which has three ports associated with it, 122 00:04:18,029 --> 00:04:21,930 FA0/5/6, and /7. 123 00:04:21,930 --> 00:04:23,460 The fourth and final command we're going to talk 124 00:04:23,460 --> 00:04:25,890 about is the show power command. 125 00:04:25,890 --> 00:04:27,750 Now, the show power command is going to be used 126 00:04:27,750 --> 00:04:30,330 to display and configure your power settings, 127 00:04:30,330 --> 00:04:32,760 particularly any devices that support PoE 128 00:04:32,760 --> 00:04:34,680 or power over Ethernet. 129 00:04:34,680 --> 00:04:36,120 By using the power command, 130 00:04:36,120 --> 00:04:36,953 we're going to be able 131 00:04:36,953 --> 00:04:39,240 to manage power distribution and troubleshoot any kind 132 00:04:39,240 --> 00:04:42,090 of power over Ethernet issues that might arise. 133 00:04:42,090 --> 00:04:43,800 When you type in the show power, 134 00:04:43,800 --> 00:04:46,710 you will get a table that shows you the power allocated, 135 00:04:46,710 --> 00:04:49,500 the power used, and the power available per port. 136 00:04:49,500 --> 00:04:51,720 In this example, you can see that I have a couple 137 00:04:51,720 --> 00:04:53,940 of different columns, including the interface, 138 00:04:53,940 --> 00:04:57,540 the admin, the oper, the power, the device, 139 00:04:57,540 --> 00:05:00,030 the class, and the max. 140 00:05:00,030 --> 00:05:01,350 When we deal with interface, 141 00:05:01,350 --> 00:05:03,360 this is going to be the switch port that we're talking 142 00:05:03,360 --> 00:05:07,620 about, such as FA0/1 or FA0/2. 143 00:05:07,620 --> 00:05:09,360 Under admin, you're going to see whether 144 00:05:09,360 --> 00:05:10,800 or not you're in automatic mode, 145 00:05:10,800 --> 00:05:13,050 which here you can see we are both set to auto, 146 00:05:13,050 --> 00:05:16,110 and for the oper, you can see if it's either on or off. 147 00:05:16,110 --> 00:05:20,010 In this case, you can see that the port at FA0/1 is on, 148 00:05:20,010 --> 00:05:22,380 and the port at FA0/2 is off, 149 00:05:22,380 --> 00:05:24,480 which means port one has power 150 00:05:24,480 --> 00:05:26,730 associated with it, but port 2 doesn't. 151 00:05:26,730 --> 00:05:27,960 We can see in the fourth column 152 00:05:27,960 --> 00:05:30,270 that this is a true statement, because we see the power 153 00:05:30,270 --> 00:05:33,690 of 15.4 watts is being shown on port 1, 154 00:05:33,690 --> 00:05:35,820 but we have a power of 0 on port 2 155 00:05:35,820 --> 00:05:37,980 because that port was turned off. 156 00:05:37,980 --> 00:05:40,080 Then we can see a short name for the device 157 00:05:40,080 --> 00:05:42,750 that's connected over PoE, and in this case, 158 00:05:42,750 --> 00:05:46,380 on port 1, we have an IP phone, there's a model 7960, 159 00:05:46,380 --> 00:05:49,740 which is a Cisco IP or voice over IP phone. 160 00:05:49,740 --> 00:05:51,940 If we look down at port 2, you can see NA, 161 00:05:51,940 --> 00:05:53,970 and that's because again, this switch port 162 00:05:53,970 --> 00:05:56,940 is currently off and not providing power to any devices, 163 00:05:56,940 --> 00:05:58,560 so that device can't be turned on, 164 00:05:58,560 --> 00:06:00,150 and reporting itself. 165 00:06:00,150 --> 00:06:02,040 The next column we have is class, 166 00:06:02,040 --> 00:06:04,920 and here you can see which class of PoE we're using, 167 00:06:04,920 --> 00:06:07,620 and in this case, on port 1 we're using class 2, 168 00:06:07,620 --> 00:06:09,000 and on port 2 since it's off, 169 00:06:09,000 --> 00:06:11,640 there is no class, or it is NA. 170 00:06:11,640 --> 00:06:13,530 The final column we have is max, 171 00:06:13,530 --> 00:06:15,720 and this tells us what is the maximum amount of power 172 00:06:15,720 --> 00:06:18,840 that can be supported by this PoE port on the switch, 173 00:06:18,840 --> 00:06:21,150 and in the case of both switch port 1 and 2, 174 00:06:21,150 --> 00:06:24,660 they are both set to a maximum of 15.4 watts. 175 00:06:24,660 --> 00:06:26,340 So, remember, for the exam, 176 00:06:26,340 --> 00:06:28,680 there are four additional network device commands 177 00:06:28,680 --> 00:06:29,880 that you should be aware of, 178 00:06:29,880 --> 00:06:31,800 and these are show MAC address table, 179 00:06:31,800 --> 00:06:35,160 show ARP, show VLAN, and show power. 180 00:06:35,160 --> 00:06:36,990 Show MAC address table is going to display 181 00:06:36,990 --> 00:06:39,060 the MAC address table on a Cisco switch, 182 00:06:39,060 --> 00:06:41,100 which shows the mapping of the MAC addresses 183 00:06:41,100 --> 00:06:43,140 to their corresponding switch ports. 184 00:06:43,140 --> 00:06:44,940 When you use the show ARP command, 185 00:06:44,940 --> 00:06:46,950 you're going to use this to display the ARP table, 186 00:06:46,950 --> 00:06:49,050 which includes the mapping of the IP addresses 187 00:06:49,050 --> 00:06:50,700 to the MAC addresses that are associated 188 00:06:50,700 --> 00:06:51,990 with that switch. 189 00:06:51,990 --> 00:06:53,790 When you use the show VLAN command, 190 00:06:53,790 --> 00:06:55,590 you're going to be able to see the VLAN settings 191 00:06:55,590 --> 00:06:58,260 for a given switch, including the names of the VLANs, 192 00:06:58,260 --> 00:06:59,430 the numbers for the VLANs, 193 00:06:59,430 --> 00:07:02,370 and what ports are associated with each of those VLANs. 194 00:07:02,370 --> 00:07:04,380 And finally, we have the show power command, 195 00:07:04,380 --> 00:07:06,750 which is going to be used to display the power settings, 196 00:07:06,750 --> 00:07:09,450 specifically those that support power over Ethernet, 197 00:07:09,450 --> 00:07:10,590 on a given switch, 198 00:07:10,590 --> 00:07:12,600 and we use this to manage our power distribution, 199 00:07:12,600 --> 00:07:14,040 and troubleshoot any kind of power 200 00:07:14,040 --> 00:07:15,303 over ethernet issues.