NET-5-IP and Routing Concepts

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.

IPv6 Address Breakdown

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.

Multicast -

A single source communicates with a single destination. 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.

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 (.). It identifies the portion of the ip address that belongs to the Network and the one that belongs to the host.

Multicast -

Addresses used to send IPv6 packets from a single host to multiple destinations.

Forwarding -

After a decision is made, the router forwards the packet to the interface from which the packet must exit to reach its destination.

Binary to Decimal

After the Positional Notation method is used to map a number's value, the positional value of each digit can be found. The next step is conversion, summarizing each of the individual values to get the result. the aim of conversion to decimal is to solve a formula.

Binary

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.

Binary to Hexadecimal

Because 16 is technically 24, conversion from base-2 to base-16 is rather easy. Each hexadecimal digit can be considered a representation of 4 binary digits. For example, 101110 is 0010 + 1110, making it 2E in hexadecimal.

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).

Routing Table

Contains lists of routes to possible network destinations. The table includes information about the network topology.

The Router

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

Dynamic Route -

Dynamic protocols include the following: D - EIGRP routing protocol O - OSPF routing protocol R - RIP routing protocol

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

Examination

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.

Calculation Tricks

For binary, there are some tricks that can make the calculation easier, instead of having to guess. One trick is to take the desired number and divide it, without the remainder, while recording each operation. If the result is even, write a 0. If it is odd, write a 1. The binary representation will appear when the operations are done. For other bases, there are other tricks and mathematical methods

Compressing IPv6 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

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

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

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.

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.

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.

No Gateway -

If there is no 'Gateway of last resort' and the destination packet is not listed, the router will discard the packet.

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.

Default Gateway Configuration

In Windows, the settings are located under Network & Internet Settings in Change Adapter Options. By default, the gateway should be received from the DHCP. if manual IPs were configured, the gateway should also be configured manually.

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.

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

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

IPv4 Structure

Network - Represents the network segment part of the IP address. Host - Represents a specific device on the network segment.

Default Gateway

Network device that can route traffic to and from other networks. A router typically fulfills this role. 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.

Hexadecimal

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. 0 1 2 3 4 5 6 7 8 9 A B C D E F 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Loopback Interface: Configuration

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.

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

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.

Static Route

Static routes are configured and recorded manually, and are identified in the routing table by the letter S.

Positional Notation

The function is the same regardless of the base being used, making it easier to perform base transitions. The function is: [number] = [digit] * [base] ^ [position].

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.

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.

Decimal to Binary

The operation can be summed up as find the X that will result in the closest number. For example, when converting the number 1994 to binary, the first step is to find X, where 2x is the closest to 1994. Continuing this process, the number should be written down and the calculation should be repeated for the remainder.

IPv4

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. It uniquely identifies devices on the network.

Decision-Making

The router decides where to forward the packet to, based on its destination IP address and the routers routing table.

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).

Encapsulation -

The router re-encapsulates the packet with new Layer 2 headers for the next hop, according to the decision made in step 3.

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.

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.

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.

Translation -

Translation allows IPv6 to communicate with IPv4-enabled devices using techniques similar to those used by NAT.

Unicast -

Unicast addresses represent specific network interfaces that support IPv6. Unicast addresses have 3 sub-types (described in the following section).

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.

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.

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.

Loopback Interface

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. Should not be confused with a loopback address.

Dual Stack -

means that a device runs both IPv4 and IPv6 protocols simultaneously. Using two stacks allows both IP versions to coexist.

IPv6 address examples

unicast: 2001:0000:130F:0000:0000:09C0:876A:130B or 2001:0:130f::9c0:876a:130b multicast: FF01::1 loopback ::1 Unspecified: ::