0. CCNA Exam Questions
4. Features in CISCO switches
1. 4.6 CDP and LLDP (CDP was already discussed in lesson 3, will focus on LLDP now)
2. 4.7 Voice VLAN !
  1. Lab 1: Did not set up Voice VLAN
  2. Lab 2: Set up Voice VLAN
5. IP Address

4rd Lesson - CCNA Fast Track (May 23, 2025). We left off at page 68.

0. CCNA Exam Questions

The CCNA exam will be using virtual devices, never real physical ones
Turing off CDP on global config level & on interface level will both be tested
LLDP and CDP will both be tested! LLDP is non-cisco proprietary, CDP is.
CCNA MC: What is a LLDP re-init time? Ans: Default is 5 seconds to implement all the changes done to the port.
CCNA Lab/ Exam: Will test you how to set up Voice VLAN
MC will test the cocepts of PCP/Priority bits
MC will test your knowledge of converting decimals to binary values
There will be no calculators on the CCNA exam

4. Features in CISCO switches

4.6 CDP and LLDP (CDP was already discussed in lesson 3, will focus on LLDP now)

Lab 1: CDP Topolgy from Router perspective (continued) [Syll pt2.3]

Last time: we talked about sh cdp neighbors g1/1 to view neighbors
Step 3: You can check the cdp neighbors in detail! sh cdp neighbors g1/1 detail
- ```bash ———————————- Device ID: Router1 Entry address(es): Platform: Cisco, Capabilities: Router Source-Router-Bridge Interface: GigabitEthernet1/1, Port ID (Outgoing port): GigabitEthernet0/0 Holdtime: 175 sec
Version: Cisco IOS Software, IOSv Software (VIOS-ADVENTERPRISEK9-M), Version 15.6(2)T, RELEASE SOFTWARE (fc2) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2016 by Cisco Systems, Inc. Compile Tue 22-Mar-16 16:19 by prod_rel_team
advertisment version: 2
Total cdp entries displayed: 1 ```

Lab 2: Configure IP Address for L2 Router into L3

Topology diagram:
L2 Router cannot check neighbor IP address

Step 1: Setup IP onto the Router1

  config t
  int g0/0
  ip address 10.0.0.1 255.0.0.0
  end

Please wait up to 1min for the new IP to take affect
Step 2: Verify cdp neighbor with detail sh cdp neighbors g1/1 detail on the Switch

----------------------------------
Device ID:  Switch1
Entry address(es):
    IP address : 10.0.0.1 <---------------------- These are NEW :D
Platform:   Cisco,  Capabilities: Router Source-Router-Bridge
Interface: GigabitEthernet1/1,  Port ID (Outgoing port): GigabitEthernet0/0
Holdtime: 175 sec

Version:
Cisco IOS Software, IOSv Software (VIOS-ADVENTERPRISEK9-M), Version 15.6(2)T, RELEASE
SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compile Tue 22-Mar-16 16:19 by prod_rel_team

advertisement version: 2
Management address(es): <---------------------- These are NEW :D
    IP address: 10.0.0.1 <---------------------- These are NEW :D

Total cdp entries displayed: 1

Note: Now IP is set up for Router1, you can remove control (i.e. ssh/telnet/…etc) to the Router!

Lab 3: Turning off cdp for Switch1 (global + interface level turn off)

Topology diagram:
Note: There are 2 ways to stop CDP
- Stopping ALL ports: Do no cdp run at global config mode
- Stopping a single port: Do no cdp run at interface config mode
Step 1a: Stopping cdp (on global level). No CDP messages will be sent/received through ALL ports.
- ```
  config t
  no cdp run
  end
```
Step 1b: Stopping cdp (on interface level). e.g. for g0/0
- ```
  config t
  int g0/0
  no cdp run
```
Step 2: Verify neighbors cannot send/receive cdp messages with sh cdp neighbors
- ```
  % CDP is not enabled
```
  Lab4: Checking more info (i.e. VTP, native VLAN, IEEE 802.1Q trunk, …) with CDP
Assume that CDP is on (I also assumed VLAN and trunk was setup)

Step 1: sh cdp neighbors g1/2 detail

  ----------------------------------
  Device ID:  Switch1
  Entry address(es):
      IP address : 10.0.0.1 <---------------------- These are NEW :D
  Platform:   Cisco,  Capabilities: Router Source-Router-Bridge
  Interface: GigabitEthernet1/1,  Port ID (Outgoing port): GigabitEthernet0/0
  Holdtime: 175 sec

  Version:
  Cisco IOS Software, IOSv Software (VIOS-ADVENTERPRISEK9-M), Version 15.6(2)T, RELEASE
  SOFTWARE (fc2)
  Technical Support: http://www.cisco.com/techsupport
  Copyright (c) 1986-2016 by Cisco Systems, Inc.
  Compile Tue 22-Mar-16 16:19 by prod_rel_team

  advertisement version: 2
  VTP Management Domain: 'FrancoDomain' 
  Native VLAN: 2 <---------------------- Removed IP Management address. These are NEW :D
  Duplex: full <---------------------- Removed IP Management address. These are NEW :D

  Total cdp entries displayed: 1

4.6.2 LLDP = Link Layer Discovery Protocol

Background:
- LLDP is a vendor neutral protocol/ non-cisco proprietary protocol (so can be used in i.e. Juniper)
- This protocol is specified by IEEE 802.1AB
- LLDP is L2 protocol and serves the same function as CDP
- Unlike CDP, which refreshes every 60s, LLDP refreshed every 30 seconds
- LLDP is disabled by default, unlike cdp!

Lab 1: Showing capabilities of LLDP

Topology Diagram:
Step 1: Verify that LLDP is off by default
- sh lldp.
```
  % LLDP is not enabled
```
Step 2: Turn on LLDP in Router1 & Switch 1. Wait up to 30 seconds to wait for LLDP message to exchange.
- lldp run for Router 1.
```
  config t
  lldp run
  end
```
- lldp run for Switch 1.
```
  config t
  lldp run
  end
```
Step 3: Verify that LLDP is able to discover neighbors in 2 ways. Either with show lldp neighbors or show lldp neighbors detail.

show lldp neighbors

  Capability codes: (R) Router,   (B) Bridge,   (T) - Telephone,
                    (C) DOCSIS Cable Device, (W) WLAN Access Point, (P) Repeater, 
                    (S) Station, (O) Other

  Device ID       Local Intrfce       Holdtme     Capability      Platform        PortID
  Router          Gig 1/1             120             R                          Gig 0/0 

                  <Local Interface: This is the neighbor>                         <PortID: This is Yourself>

  Total cdp entries displayed : 1

Note: The hold time is ALWAYS 120s, the count down process is NOT visable in LLDP, unlike in CDP.

This time with detail: show lldp neighbors detail. ```bash ———————————- Device ID: Router1 Entry address(es): Platform: Cisco, Capabilities: Router Source-Router-Bridge Interface: GigabitEthernet1/1, Port ID (Outgoing port): GigabitEthernet0/0 Holdtime: 175 sec
Version: Cisco IOS Software, IOSv Software (VIOS-ADVENTERPRISEK9-M), Version 15.6(2)T, RELEASE SOFTWARE (fc2) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2016 by Cisco Systems, Inc. Compile Tue 22-Mar-16 16:19 by prod_rel_team
Time remaining: 97 seconds System Capabilities: B, R Enabled Capabilities: R <—— Only Router Management Addresses: IP: 10.0.0.1 <—— IP is visable Auto Negotiation - Not Supported Physical media capabilities - not advertised Media Attachment Unit type - not advertised Vlan ID: - not advertised
Total entries displayed: 1 <—— the word ‘cdp’ is removed

#### Lab 2: Checking what other lldp commands is available in the console

- 
```bash
config t
int g1/1
lldp ?

This is the output of lldp ? under interface config mode
- ```
  switch1(config-if) #lldp ?
  med-tlv-secret      Selection of LLDP MED TLVs to send
  receive             Enable LLDP reception on interface
  tlv-select          Selection of LLDP TLVs to send
  transmit            Enable LLDP transmission on interface
```
- We only have to pay attention to the 2 lddp commands for on/off:
  - lldp receive & lldp no receive = Allowing/ Dis-allowing port to receive LLDP messages
  - lldp transmit & lldp no transmit = Allowing/ Dis-allowing port to transmitting LLDP messages

Lab 3: Resetting LLDP re-initilization delay timer away from the default 5 seconds.

LLDP Re-initialization time = The delayed time for LLDP to be re-useable
Adjusting the LLDP reinit time can avoid frequent initialization causing by frequent settings changes to LLDP
Step 1: Re-init the time for LLDP port
- ```
  config t
  lldp reinit 5
  end
```

Step 2: Verify lldp information with sh lldp:

  GLobal LLDP Information:
  Status: ACTIVE
  LLDP advertisements are sent every 30 seconds
  LLDP hold time advertised is 120 seconds
  LLDP interface reinitialization delay is 5 seconds

4.7 Voice VLAN !

Meaning: Voice VLAN = a VLAN for sending VoIP/ Voice Over IP data frames (i.e. those that are sent/received by IP Phones)
Usually the topology for Voice VLAN:
Why do we need the Voice VLAN feature ? AKA why not send data frames through normal VLAN ? Why use Voice VLAN
- Voice VLAN can distinguish normal user data frames vs voice data frame
- Without this distinguishing the two, voice data frame quality can be greatly affected (Since voice is sensitive to delay & packet drops)
Let’s do some labs

Lab 1: Did not set up Voice VLAN

This is the current topology diagram:

en
config t
vlan 2
name Accounting
int g0/2
switchport access vlan2
end

Notice: User PC – data –> Cisco IP Phone – data –> Switch
There is no tag in the data frame
If the bandwidth is HUGE then there won’t be any package drop/ delay but vice versa, it will cause some issues.

Lab 2: Set up Voice VLAN

To fix the issue: Additionally configure Voice VLAN on access port by the interface mode switchport voice vlan <VLAN ID>
IP Phone will get the Voice VLAN settings via CDP, thus tagging all the VoIP traffic with the VLAN 200 tag.
This is the current topology diagram:

en
config t
vlan 2
name Accounting

vlan 200
name Voice
int g0/2
switchport access vlan 2
switchport voice vlan 200
end

Q: What is a pirority bit?
- Ans: Priority bit/ Priority/ PCP (Priority Code Point)/ CoS (Class of Service) bits are the initial 3bit field tag for handling voice data frames under a priority queue
- Usually this piroirty bit is 5 in decimal, in binary, it’s 101 (during phone call, actively exchanging voice data frames)
  - It’s 011 in binary, when the call is still connecting/ dialing
There are 3 parts to the enriched data frame that is getting sent through VLAN 200:
- The 3 bit priority bit/ PCP : i.e. 101 in binary or 5 in decimal
- The VLAN 200 tag, i.e. 200
- original data frame

5. IP Address

5.1 IP Address’s structure

There are 2 IP address formats:
- in binary
- in decimal
Each IP is 32 bits long = 4 * 8 bit fields (octets) = 4 octets
These octets are separated by periods
Each octet can live between the range 0 ~ 255 in decimal (00000000 ~ 11111111 in binary)

5.2 Binary numbers

Converting from binary to decimal
- 00000000 in binary = 0 in decimal
- 00010001 in binary = 20 + 24 = 1 + 16 = 17 in decimal
Converting from decimal to binary
- e.g. 30 = 30/2 = 15 R 0, 15/2 = 7 R 1, 7/2 = 3 R 1, 3/2 = 1 R 1, 1/2 = 0 R 1
  - Start from the bottom you’ll get 11110 = 16 + 8 + 4 + 2 + 0 = 30 (which is our answer !)
Concept of bits:
- 1 bit: Either 0 or 1 (maximum 2 combinations)
- 2 bits: Either 00, 11, 01, 10 (maximum 4 combinations)
- 3 bits: Either 000, 001, 010, 011, 100, 101, 110, 111 (maximum 8 combinations) . . .
- 24 bits: Either …. (maximum 16,777,216 combinations = 2**24)

5.3 Discussing Network ID without subnetting

There are 4 classes. Class A,B,C,D; Each class uses different lengths/number of Network ID bits

5.3.1 Class A: 1-126

Format: The 4 octets = Network ID + Host ID + Host ID + Host ID. However there are 4 rules to follow!!
Rule 1: Class A’s first octet = The Network ID must be from 1 - 126 (Excluding 0 and 127 !!!) (withholding prefix starting with 0 hence the range is 00000000 ~ “00000001 ~ 01111110” ~01111111)
- 0: or 0.0.0.0 is reserved as this host on the network
  - 0.0.0.0 is used as the source IP address, for a device that yet to have an IP, the device requests an IP via DHCP to talk to 0.0.0.0 to request an IP on the network.
  - Note: 0 is not considered as class A
- 1-126: Normal Class A IP Address
- 127: Reserved for internal loopback and testing (i.e.127.0.0.1)
  - Most OS when you ping 127.0.0.1 you can verify whether your TCP/IP protocol stack is healthy and corrected installed
  - pinging 127.0.0.1 with 32 bytes of data: Reply from 127.0.0.1: bytes=32 time<1ms TTL=128 Reply from 127.0.0.1: bytes=32 time<1ms TTL=128 Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Rule 2: First octet/ First 8 bits = The class A’s NetworkID. The next 24 bits represent the HostID
Rule 3: For a useable HostID to represent a network but not a host, the rest of the host IDs bits cannot be all 0s
- Represents a network: 125.0.0.1
- Represents just a host: 10.0.0.0, 111.0.0.0
Rule 4: To become a valid Host IP Address, the rest of the host IDs bits cannot all be 1 (i.e. 11111111 in binary = 255 in decimal)
- Represents a network: 125.0.0.1
- Represents a directed broadcast: 10.255.255.255, 111.255.255.255

5.3.2 Class B: 128-191

Format: The 4 octets = Network ID + Network ID + Host ID + Host ID. Again, there are 4 rules to follow!!
Rule 1: Class B’s first octet = The Network ID must be from 128 - 191 (withholding prefix starting with 10 hence the range is 10000000 ~ 10111111)
Rule 2: Class B’s first 2 octets = Network ID, the next 2 octets = Host ID
Rule 3: To become a valid host IP address. The last 2 octets bits cannot be all 0s
- Represents this network: 172.16.0.0 (the last 2 octets are 0)
- Represents this host: 172.16.0.1 (the last 2 octets are NOT 0)
Rule 4: To become a valid host IP address. The last 2 octets bits cannot be all 1s (i.e. 11111111 in binary = 255 in decimal)
- Represents this network: 172.16.254.255 (the last 2 octets are 1s)
- Represents a directed broadcast: 172.16.255.255 (the last 2 octets are NOT 1s)

5.3.3 Class C: 192-223 (We use this at home)

Format: The 4 octets = Network ID + Network ID + Network ID + Host ID. Again, there are 4 rules to follow!!
Rule 1: Class C’s first octet = The Network ID must be from 192 - 223 (withholding prefix starting with 110 hence the range is 11000000 ~ 11011111) =
Rule 2: Class C’s first 3 octets = Network ID, the last octet = Host ID
Rule 3: To become a valid host IP address. The last octet bit cannot be 0
- Represents this network: 192.16.0.0 (the last octet is 0)
- Represents this host: 192.16.0.1 (the last octet is NOT 0)
Rule 4: To become a valid host IP address. The last octet bit cannot be 1 (i.e. 11111111 in binary = 255 in decimal)
- Represents this network: 172.16.254.254 (the last octet is 1)
- Represents a directed broadcast: 172.16.255.255 (the last octet is NOT 1)

5.3.4 Class D: 224-239

Rule 1: Class D’s first octet = The Network ID must be from 224-239 (withholding prefix starting with 1110 hence the range is 11100000 ~ 11101111)
Class D is used for multi-casting
Topology of uni-cast vs multi-cast
- uni-cast
- multicast

5.3.5 Class E: 240 - 255

Rule 1: Class E’s first octet = The Network ID must be from 240 - 255 (withholding prefix starting with 11110 hence the range is 11110000 ~ 11110111)
Class E is reserved for future use (reserved for IPv6 now)

Special address: 255.255.255.255 - local broadcast

- When a host computer sends a local broadcast packet, this packet will be accepted by all other host PCs on the local network! (With excepts to router, as router does not forward packages like these)
- Local Broadcast topology:
    - ![](../../../../../assets/images/ccna/lesson4/lesson_4_local_broadcast_1.jpg)

5.x.3 Simulation labs!

Please refer to this website for simulation

Simulation Lab 1 (CCNA Exam Practical Style 1): Switch, VLAN

Task 1: Switch 1 needs to initiate vlan12 and vlan 34. Switch 2 needs only vlan 12. Please verify the proper setup using sh vlan brief
Techniques: copy run start allows you to save configs for the exam
Task 2: Setting up VLAN 99, and don’t forget to include the switchport e0/1 for that. Please wait for the access port to warm up…otherwise, you might screw yourself…
Task 3: No trunk, so we’re using access trunk, switchport access vlan12
Task 4: IP Phone
Task 5: Neighbor discovery protocol (use CDP), turn off cdp for the port!

Simulation Lab 2 (CCNA Exam Practical Style 2):: LARP EtherChannel = bundling

Task 1: Setting up channel group to be ALL active (this might change in the real exam, i.e. one passive, one active)
Task 2: EhterChannel trunk link set up, verify with sh vlan brief
Task 3: Careful with the dot1q command. 2 switches needs to be set.
Task 4: untag data frames = native VLAN (This part must be set up first before everything else)
Important ! Define the dot1Q first, before you set up your trunks

Simulation Lab 3 (CCNA Exam Practical Style 3): Different VLAN and different switches

Task 0: Don’t touch the VTP settings and define the 2 VLANs yourself, VLAN 202 and VLAN 303
Task 1-3:
- Switch 1: Need only VLAN 303
- Switch 2: Need both VLAN 202 and VLAN 303, int just 1 port
- Switch 3: Need both VLAN 202 and VLAN 303, int 2 ports (i.e. int e0/3 for allowing both VLAN 202 and VLAN 303)
Performing sanity checks: please check with sh int trunk

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