Networking, Chapter 5

What is the default suffix of an IPv6 address?

/64

How many bits are in an IP or subnet mask address?

32

What is an octet?

8-bit string (IPv4 consists of four octets).

What is a bit?

A bit (binary digit) is the smallest unit of data in a computer. A bit has a single binary value, either 0 or 1.

A loopback interface is created using

A loopback interface is created using the commandinterface loopback <ID>via the configuration terminal

The Router

A router is a device designed to receive, forward, and analyze packets transmitted to and from other devices on a network, and other networks. Routers enable inter-network communication, and can provide services such ACL and NAT, which are required in any networking scheme. A router is a Layer 3 device that communicates using IP addresses

Subnet Mask

A subnet mask is a 32-bit address, the same as an IP address. Like an IPv4 address, a subnet mask consists of 4 octets, separated by dots (.). Two similar IP addresses can belong to completely different networks, depending on the subnet mask. Subnet masks will be further explained in the next module.

What is a suffix?

A suffix is a decimal method of displaying a subnet mask based on bits. For example: /8 > 255.0.0.0

Structure

An IPv4 address consists of two parts: network and host, defined by the subnet mask. Network - Represents the network segment part of the IP address. Host - Represents a specific device on the network segment.

Section 4: IPv4

An Internet Protocol (IP) is a numerical label assigned to devices connected to a network. It is used for host identification and communication. The public IP address space is managed by IANA (Internet Assigned Numbers Authority) and divided into five regional Internet registries (RIRs), each responsible for their designated territories. Each RIR is responsible for address assignment to users and service providers.

Which mathematical base does the hexadecimal system use, and which digits represent it?

Base 16, 10 digits and 6 characters: 0-9, A, B, C, D, E, F

Which mathematical base does the binary system use, and which digits represent it?

Base 2, two digits: 0 and 1

Based on which two items of information does a router make routing decisions?

Based on the destination packet IP and the routing table.

What do the letters C and L represent in the routing table?

C = Directly connected network L = Local interface IP address

What is the purpose of IPv4 Class D?

Class D IP range is reserved for multicast communications.

Other Router Interfaces

Console - This is a physical management port, visually similar to Ethernet ports, that provides out-of-band access to a Cisco device. Out-of-band refers to access via a dedicated management channel used only for device maintenance. AUX - (not the one used for audio) The auxiliary port mainly functions as a backup console port, although it can also be used as a dial-up port for remote management, and other purposes. The main difference between Console and AUX is that AUX pushes output to the port after power-up, while a Console does so during the power-up process itself

Fast Ethernet Interface

Fast Ethernet was first made public in 1995. Ethernet operates at a speed of 100 Mbps and uses the media standard 100BaseT.

Addresses

IPv4 addresses consist of 32 bits and are divided into four octets, each containing 8 bits. This addressing method provides 4,294,967,296 (2^32) IPv4 addresses in total. An IP address represented in binary will appear as follows: 192.168.1.1 = 11000000.10101000.00000001.00000001

IPv4 Addresses

IPv4 addresses consist of 32 bits and are divided into four octets, each containing 8 bits. This addressing method provides 4,294,967,296 (2^32) IPv4 addresses in total. An IP address represented in binary will appear as follows: 192.168.1.1 = 11000000.10101000.00000001.00000001

Name two IPv6 Unicast address types.

IPv6 Unicast types: Global Unicast (the equivalent of an IPv4 public address). Link-local FE80::/10 (the equivalent of an IPv4 APIPA address). Loopback ::1/128 (the equivalent of an IPv4 loopback address). Unique-local FC00::/7 (the equivalent of an IPv4 private address).

What are the three IP address ranges used in private networks?

In accordance with RFC1918, the following ranges are assigned to private networks: 10.0.0.0-10.255.255.255 172.16.0.0-172.31.255.255 192.168.0.0-192.168.255.255

Loopback

Loopback addresses represent the same interface in a computer. In IPv4, an entire network (127.0.0.0/8) is reserved for loopback addresses. Almost all leading operating systems use the name "localhost" to represent IPv4 loopback address 127.0.0.1. The IPv6 address reserved for loopback is: 0000:0000:0000:0000:0000:0000:0000:0001/128

Routing Table

The Routing Table contains lists of routes to possible network destinations. The table includes information about the network topology. The codes on the left side of a route show how the network is learned by the router

The command show ip route displays

The command show ip route displays the routing table and is run in the Enable mode.

Classful Addressing

This type of addressing architecture was used from 1981 to 1993, when the CIDR originated. It categorizes the IPv4 address space into 5 different classes. The categories are based on the address's first octet.

Device Communication Types

Unicast - Unicast addresses represent specific network interfaces that support IPv6. Unicast addresses have 3 sub-types (described in the following section). Multicast - Addresses used to send IPv6 packets from a single host to multiple destinations. Anycast - IPv6 unicast addresses that can be assigned to multiple devices. Packets sent to an Anycast address are routed to the nearest device that has that address (which is why Anycast is also known as "one to the nearest"). This method operates similar to IPv4 broadcast.

verify settings for both User1 and User2.

ipconfig

How long is an IPv6 address in bits?

128

What is the difference between an IPv4 unicast message and an IPv4 broadcast message?

A unicast message only has a single destination, while a broadcast message is sent to the entire broadcast domain (all devices on the same network).

Internet Protocol (IP)

An Internet Protocol (IP) is a numerical label assigned to devices connected to a network. It is used for host identification and communication. The IP address space is managed by IANA (Internet Assigned Numbers Authority) and divided into five regional Internet registries (RIRs), each responsible for their designated territories. Each RIR is responsible for address assignment to users and service providers.

Binary

Binary is an alternative number system that consists of only two numbers: 0 and 1. This system is used by computers, which communicate by modulating electrical currents. Because there are only two numbers, the system is known as the base-2 numeral system.

Routing Table Codes

Directly Connected / Local Route When inspecting the routing table, records identified by the codes Cor L indicate directly connected networks. The codes mean that the devices are connected to the physical layer. The Cand L records are automatically created Static Route Static routes are configured and recorded manually, and are identified in the routing table by the letter S. Dynamic Route Dynamic routes are identified with unique letters that indicate the dynamic protocol, as follows: D -EIGRP routing protocol O -OSPF routing protocol R -RIP routing protocol

Routing Table Codes

Directly-Connected / Local Route - When inspecting the routing table, records identified by the codes C or L indicate directly connected networks. The codes mean that the devices are connected to the physical layer. The C and L records are automatically created. Static Route - Static routes are configured and recorded manually, and are identified in the routing table by the letter S. Dynamic Route - Dynamic routes are identified with unique letters that indicate the dynamic protocol that was used to create them. Dynamic protocols include the following: D - EIGRP routing protocol O - OSPF routing protocol R - RIP routing protocol

Routing Process

Examination In the first step, the router decides whether to process a packet or ignore it. Routers will ignore packets with errors, or packets they don't know how to process. Decapsulation The router examines the Layer 2 address to decide if the packet was intended for itself (the default gateway), and verifies the integrity of the frame using the FCS (Layer 2 trailer). Decision-Making The router decides where to forward the packet to, based on its destination IP address and the routing table Encapsulation The router re-encapsulates the packet with new Layer 2 headers for the next hop, according to the decision made in step 3. Forwarding After a decision is made, the router forwards the packet to the interface from which the packet must exit.

Router Interfaces

Fast Ethernet - First made public in 1995. Operates at a speed of 100 Mbps and uses the media standard 100BaseT. Gigabit Ethernet - Introduced in 1999. Supports a faster speed of 1000 Mbps, and uses the media standard 1000BaseT, but can also support 100 Mbps. Serial Interfaces - Used for long distance transmissions. If two serial ports need to communicate with each other, they must be synchronized with the same clock frequency and allocate the necessary bandwidth.

What is a default gateway address?

From the host perspective, the default getaway is the address of the router that routes traffic to other networks.

Gigabit Ethernet Interface

Gigabit Ethernet was introduced in 1999, and it supports a faster speed of 1000 Mbps. It uses the media standard 1000BaseT, but can also support 100 Mbps.

Unicast Types

Global Unicast - IPv6 global unicast addresses are similar to IPv4 public addresses. They are unique and can be routed via the Internet. IANA currently assigns only 2000::/3 addresses. Link-Local - Addresses that enable communication between devices in the same local link (LAN). Link Local addresses must be unique only within the link. They are not guaranteed to be unique beyond their network segment, and begin with FE80::/10. Unique-Local - Similar to IPv4 private addresses, with minor differences. Unique addresses should not be routable in the global IPv6, and should not be translated to global IPv6 addresses. They begin with FC00::/8.

Hexadecimal Conversion

Here is how binary is converted to hex, with an example. Conversion steps: • Divide the binary number into groups of 4 digits. • Convert each group to its equivalent hex value using the Base Comparison table. • Merge the results of each group. Conversion example: Convert 0111111111010100 to Hex • 0111 1111 1101 0100 • 0111 = 7, 1111 = F, 1101 = D, 0100 = 4 • Answer is 7FD4

Hexadecimal

Hex, or Hexadecimal, is a number system that consists of 16 characters and is known as the base-16 numeral system. Hex uses the numbers 0-9, followed by the letters A-F. Hex is widely used as an alternative representation to binary, since it is a more human-oriented system.

What is the corresponding IPv6 term for an IPv4 octet?

Hextet.

IPv4 and IPv6 Coexistence

IPv4 and IPv6 can coexist using protocols and tools created by IEFT, which are known as: Dual Stack, Tunneling, and Translation. Dual Stack - Dual Stack means that a device runs both IPv4 and IPv6 protocols simultaneously. Using two stacks allows both IP versions to coexist. Tunneling - Tunneling is used when IPv6 addresses are to be sent over IPv4 networks, or vice versa. In this method, the IPv6 packet is encapsulated within an IPv4 packet. Translation - Translation allows IPv6 to communicate with IPv4-enabled devices using techniques similar to those used by NAT.

Compressing IPv6 Addresses

IPv6 addresses are long and difficult to read. Some rules exist to omit specific numbers to simplify the addresses. Full Address - A full address contains all 8 blocks, with 4 hexadecimal digits. Example of a full IPv6 address: 2001:0000:3238:0001:0063:0000:0000:FEFB Leading Zeros - The first rule allows us to discard leading zeros in a block, making the address a bit shorter: 2001:0:3238:1:63:0000:0000:FEFB Consecutive Zeros - If two or more blocks contain consecutive zeros, they can be omitted and replaced with double colon signs (::) resulting in: 2001:0:3238:1:63::FEFB Note that omitting is allowed only once in the address. Zero Block - If there is a block that consists of 4 zeros, but without a consecutive zero-filled block, it can be replaced with a single zero, and the final address will be: 2001:0:3238:1:63::FEFB

Suffix Calculation

Just like the IPv4 address, the subnet mask is constructed of 4 octets (8 bits each). The suffix is a simple representation of the subnet mask, using less characters, and is placed after the IPv4 address. The suffix will be written in correspondence to the number of bits set to 1 in the subnet mask. 8 bits = 255.0.0.0/8 16 bits = 255.255.0.0/16 24 bits = 255.255.255.0/24 32 bits = 255.255.255.255/32

Link-Local

Link-Local addresses, also known as APIPA addresses, are valid only for communication within the network broadcast domain. The entire 169.254.0.0/16 address range is reserved for Link-Local. If the DHCP is not available or an IP is not statically configured, the OS will randomly generate a Link-Local address. Link-Local addresses are not guaranteed to be unique outside their network segments, which is the reason why routers do not forward their packets.

Loopback Interface

Loopback is a logical interface that is not assigned to a physical port. The interface can be used to test and manage Cisco IOS devices, because it ensures that at least one interface will always be available. It can also be used in the OSPF identification process A loopback interface should not be confused with a loopback address.

Loopback Interface

Loopback is a logical interface that is not assigned to a physical port. The interface can be used to test and manage Cisco IOS devices, because it ensures that at least one interface will always be available. A loopback interface should not be confused with a loopback address. Configuration A Loopback Interface is often configured during the initial router configuration, mainly for testing purposes. The interface is configured to automatically be ready for operation. A router can have more than one loopback interface enabled simultaneously, but each interface must have a unique IP. A loopback interface is created using the command interface loopback <ID> via the configuration terminal.

Section 5: IPv6

Over the years, the IPv4 address pool was slowly depleted due to technical progress that led to more and more devices around the world being connected to the Internet. IPv6 was designed to solve the IPv4 address limitation and provide additional enhancements. IPv6 has a larger 128-bit address pool, with the number of available addresses being 340*1036. Example of an IPv6 address: 2001:0000:3238:0001:0063:0000:0000:FEFB

Public vs Private

Private IPs are non-unique global addresses that can belong to one of three IP address ranges. They are used to create networks that do not communicate over the Internet. The same private IPs can be found in multiple separate networks and can be used freely. Public addresses are used for communication over the Internet. These IP addresses must be unique, require a fee, and are purchased from service providers. A router will typically have both a private IP on one NIC, and a public IP on another NIC. For example, the address 8.8.8.8 is a public address used by Google.

What is the difference between a public IP address and a private IP address?

Private addresses are only allowed on the LAN and are used to represent internal hosts. Public addresses are unique, only allowed on the internet, and are used to represent large networks (AS).

Private IP Ranges

Private addresses are used in networks designed for homes and organizations. The ranges differ according to the amount of separate networks and computers in each network, and there are no enforced rules.

Interface Configuration

Router interfaces need to be set up with IP addresses, similar to computer network interfaces. The interface [type] [id] command selects the desired interface. To use an interface, it must be set up with ip address [ip] [subnet mask] and enabled using the no shutdown command. Use show ip interface brief to verify interface settings on the router.

Routing Choices

Same LAN If the destination IP is on the same LAN as the source device, there is no need for routing. The frame will get to the destination via the switch. Known Route If the destination IP is on a different LAN, but the network device has a static or dynamic route to the destination IP, it will forward the packet to the next hop, based on the route. No Route If there is no static or dynamic route in the network device's routing table, it will forward the packet to its default 'gateway of last resort No Gateway If there is no 'gateway of last resort' and the destination packet is not listed, the router will discard the packet.

Routing Choices

Same LAN - If the destination IP is on the same LAN as the source device, there is no need for routing. The frame will get to the destination via the switch. Known Route - If the destination IP is on a different LAN, but the network device has a static or dynamic route to the destination IP, it will forward the packet to the next hop, based on the route. No Route - If there is no static or dynamic route in the network device's routing table, it will forward the packet to its default 'Gateway of last resort'. Note that a 'Gateway of last resort' is where the router will send packets to if there is no other known route to which they should be sent. No Gateway - If there is no 'Gateway of last resort' and the destination packet is not listed, the router will discard the packet.

Serial Interface

Serial interfaces are used for long distance transmissions. If two serial ports need to communicate with each other, they must be synchronized with the same clock frequency and allocate the necessary bandwidth.

AUX

The auxiliary port mainly functions as a backup console port, although it can also be used as a dial-up port for remote management, and other purposes. The main difference between Console and AUX is that AUX pushes output to the port after power-up, while a Console does so during the power-up process itself.

Default Gateway

The default gateway is a network device that can route traffic to and from other networks. A router typically fulfills this role. The default gateway is similar to the door of a room. If the desired object is in another room, the object can be reached only by exiting the current room and entering the other room through the door. If the destination is on the same network, there is no need to pass through the router. Configuration Default gateway configuration options are typically located together with other adapter configuration options. In Windows, the settings are located under Network & Internet Settings in Change Adapter Options. By default, the gateway should be received from the DHCP. However, if manual IPs were configured, the gateway should also be configured manually.

Default Gateway

The default gateway is a network device that can route traffic to and from other networks. A router typically fulfills this role. The default gateway is similar to the door of a room. If a desired object is in another room, the object can be reached only by exiting through the door. If the destination is on the same network, there is no need to pass through the router.

Decimal -

The most common numbering system consists of ten numbers, 0-9, and it is called the decimal system. The system is based on the 10 fingers we use to count and is known as the base-10 numeral system.

Routing Process

The routing process involves selecting a path for the delivery of packets across different networks, from source to destination, through Layer 3 devices. It is important to note that routers can route packets to directly connected networks, without requiring configuration. However, if the networks are not connected directly to the router, the route needs to be learned. Routing decisions are made based on a router's routing table. Process Stages Examination - In the first step, the router decides whether to process a packet or ignore it. Routers will ignore packets with errors, or packets they don't know how to process. Decapsulation - The router examines the Layer 2 address to decide if the packet was intended for itself (the default gateway), and verifies the integrity of the frame using the FCS (Layer 2 trailer). Decision-Making - The router decides where to forward the packet to, based on its destination IP address and the routers routing table. Encapsulation - The router re-encapsulates the packet with new Layer 2 headers for the next hop, according to the decision made in step 3. Forwarding - After a decision is made, the router forwards the packet to the interface from which the packet must exit to reach its destination.

The Routing Process

The routing process involves selecting a path for the delivery of packets across different networks, from source to destination, through Layer 3 devices. It is important to note that routers can route packets to directly connected networks, without requiring configuration. However, if the networks are not connected, the route needs to be learned Routing decisions are made based on a routing table.

IPv6 Address Breakdown

The suffix represents the prefix portion of the address. IPv6 does not use notation subnet masks like IPv4. The prefix length indicates the network portion. 1. Because the prefix is /64, the first 64 bits in the address represent the network portion. 2. The 16 bits from the 49th to the 64th are for defining subnets. 3. The remaining 64 bits represent the host portion in the IPv6 address. 4. The prefix range can be from 0 to 128, with the most common being /64.

What are the three parts of an IPv6 with a suffix of /64?

The three parts are: First 45 bits (3 Hextets) - Global routing prefix, global identifier. First 16 bits (1 Hextet) - Subnet ID, network identifier. Last 64 bits (4 Hextets) - Interface ID, host identifier.

Console

This is a physical management port, visually similar to Ethernet ports, that provides out-of-band access to a Cisco device. Out-of-band refers to access via a dedicated management channel used only for device maintenance.

Configure and Verify IPv6

To enable IPv6 routing, enter the configuration terminal mode, and run the command ipv6 unicast-routing. Configure IPv6 on a router interface using the command ipv6 address. Verify the configuration using the command show ipv6 interface brief.

Communication Types

Unicast - The most basic form of IP communication is one-to-one, where a packet is sent directly from one device on the network to another device on the network. A single source communicates with a single destination. Multicast - Multicast is when a single source communicates with multiple destinations. A packet is sent from one device on the network to a group comprised of one or more devices, using Class D addresses. Broadcast - Broadcast is when a packet is sent from one device on the network to all other devices on the network, using a generic broadcast address (255.255.255.255 for IPv4, or FF:FF:FF:FF:FF:FF for IPv6).

Verify Connectivity

Use ipconfig to verify network settings

show ip interface brief

Use show ip interface brief to verify interface settings on the router.

A router is a

device designed to receive, forward, and analyze packets transmitted to and from other devices on a network, and other networks. Routers enable inter-network communication, and can provide services such ACL and NAT, which are required in any networking scheme. A router is a Layer 3 device that communicates using IP addresses.

Verify the status and IP configuration, using

do show ip interface brief

Display the routing table using

do show ip route

The do command enables the

privileged mode command in global configuration mode. It does not support the autocomplete feature.