Questions 5

What does the ARP command tell you?

ARP Command. Using the arp command allows you to display and modify the Address Resolution Protocol (ARP) cache. An ARP cache is a simple mapping of IP addresses to MAC addresses. ... For example, suppose you can't access a computer that has an IP address of 192.168.168.100.

How does ARP work in Layer 3?

ARP is a service protocol that glues together layer 2 and layer 3 protocols. It solves the problem that you need to add a layer 2 (MAC) destination address over a shared media like Ethernet or Wireless LAN using IP packets. But ARP is a separate process with separate packets.

What do you mean by classless addressing?

Classless IP addressing means you can use any subnetmask you want, even assigning partial blocks. For example subnet 172.16.0.0 is a class B network.

What do you mean by Address Resolution?

What does Address Resolution mean? Address resolution or name resolution is the process of acquiring a physical address from a machine or virtual address that a network node or computer peripheral has sent.

Network, Host, and Broadcast Addresses

Each network address contains (or identifies) host addresses and a broadcast address. The concepts discussed in this topic form the basis for understanding IPv4 addressing. Make sure you understand how a network address identifies a network portion and host portion using the subnet mask or prefix length and the ANDing operation. Also make note of the various types of network addresses within a network.

there are three options for RA messages:

Option 1: SLAAC · Option 2: SLAAC with a stateless DHCPv6 server · Option 3: Stateful DHCPv6 (no SLAAC)

What does SLAAC stand for?

Stateless Address Auto-configuration

Global Routing Prefix

This is the first three groups of numbers, and it defines the "network" of the address.

Does router use ARP?

When ARP is used by a host in a LAN, then it is broadcast because the host does not know where is the destination host, but a router knows which interface it must use to get to the next router. ... This arp table entry will be used to map the next-hop IP address to the MAC address of the receiving router.2

What is the broadcast address of the network?

broadcasting a packet to an entire IPv4 subnet using the private IP address space 172.16.0.0/12, which has the subnet mask 255.240.0.0, the broadcast address is 172.16.0.0 OR 0.15.255.255 = 172.31.255.255.

Classless Addressing

the classful system allocated 50% of the available IPv4 addresses to 128 Class A networks, 25% of the addresses to Class B and then Class C shared the remaining 25% with Class D and E. The problem is that this wasted a great deal of addresses and exhausted the availability of IPv4 addresses. Not all organizations' requirements fit well into one of these three classes. For example, a company that had a network with 260 hosts would need to be given a class B address with more than 65,000 addresses wasting 64,740 addresses. Classful addressing was abandoned in the late 1990s for the newer and current classless addressing system. However, there are still classful remnants in networks today. For example, when you assign an IPv4 address to a computer, the operating system examines the address being assigned to determine if this address is a class A, class B, or class C. The operating system then assumes the prefix used by that class and makes the default subnet mask assignment. The system in use today is referred to as classless addressing. The formal name is Classless Inter-Domain Routing (CIDR, pronounced "cider"). In 1993, the IETF created a new set of standards that allowed service providers to allocate IPv4 addresses on any address bit boundary (prefix length) instead of only by a class A, B, or C address. This was to help delay the depletion and eventual exhaustion of IPv4 addresses. The IETF knew that CIDR was only a temporary solution and that a new IP protocol would have to be developed to accommodate the rapid growth in the number of Internet users. In 1994, the IETF began its work to find a successor to IPv4, which eventually became IPv6.

Why ARP is required?

Typically, a host uses ARP to determine the hardware address of another host. Your system maintains a table that maps IP addresses to MAC addresses of different systems and routers on your network. ... The ARP protocol creates entries as needed.

What is the subnet mask of Class B?

255.255.0.0 To divide a given network address into two or more subnets, you use subnet masks. The default subnet masks for class A networks is 255.0.0.0, for class B is 255.255.0.0, and for class C is 255.255.255.0, which signify a network without subnets.

Global Unicast

A global unicast address is similar to a public IPv4 address. These are globally unique, Internet routable addresses. Global unicast addresses can be configured statically or assigned dynamically.

What is the primary purpose of ARP?

What is the primary purpose of ARP? translate URLs to IP addresses resolve IPv4 addresses to MAC addresses provide dynamic IP configuration to network devices convert internal private addresses to external public addresses 2.

Destination or Service Unreachable

When a host or gateway receives a packet that it cannot deliver, it can use an ICMP Destination Unreachable message to notify the source that the destination or service is unreachable. The message will include a code that indicates why the packet could not be delivered. Some of the Destination Unreachable codes for ICMPv4 are: · 0 - Net unreachable · 1 - Host unreachable · 2 - Protocol unreachable · 3 - Port unreachable Note: ICMPv6 has similar but slightly different codes for Destination Unreachable messages.

RA Option 2: SLAAC and Stateless DHCPv6

With this option, the RA message suggests devices use: · SLAAC to create its own IPv6 global unicast address. · The router's link-local address, the RA's source IPv6 address for the default gateway address. · A stateless DHCPv6 server to obtain other information such as a DNS server address and a domain name. A stateless DHCPv6 server distributes DNS server addresses and domain names. It does not allocate global unicast addresses.

unicast transmission

A method for data transfer from a source address to a destination address.

Is netmask the same as subnet?

A netmask is a 32-bit mask used to divide an IP address into subnets and specify the network's available hosts. In a netmask, two bits are always automatically assigned. For example, in 255.255.225.0, "0" is the assigned network address. In 255.255.255.255, "255" is the assigned broadcast address.

IPv6 Prefix Length

A number written as /x, where x is an integer between 0 and 128 inclusive, that defines the number of initial bits in an IPv6 address, used for IPv6 subnetting and for matching with IPv6 ACLs.

Address Resolution Protocol (ARP)

A protocol in the TCP/IP suite used with the command-line utility of the same name to determine the MAC address that corresponds to a particular IP address.

multicast transmission

A transmission method in which data is sent from a server to specific nodes that are predefined as members of a multicast group.

What layer is ARP?

ARP is layer 2. The reason being is that a broadcast is sent on layer 2 (data link layer) and ARP will normally not traverse to layer 3 (network layer). However it can provide extra features to the layer 3 protocol. The truth is that not all protocols fit the OSI model exactly, because after all it's just a model.

What does ARP poisoning do?

ARP spoofing is a type of attack in which a malicious actor sends falsified ARP (Address Resolution Protocol) messages over a local area network. This results in the linking of an attacker's MAC address with the IP address of a legitimate computer or server on the network.

How does ARP resolve an IP address?

ARP stands for Address Resolution Protocol. When you try to ping an IP address on your local network, say 192.168.1.1, your system has to turn the IP address 192.168.1.1 into a MAC address. This involves using ARP to resolve the address, hence its name.

Dynamic Link-Local Addresses

All IPv6 devices must have an IPv6 link-local address. A link-local address can be established dynamically or configured manually as a static link-local address. Figure 1 shows the link-local address is dynamically created using the FE80::/10 prefix and the Interface ID using the EUI-64 process or a randomly generated 64-bit number. Operating systems will typically use the same method for both a SLAAC created global unicast address and a dynamically assigned link-local address, as shown in Figure 2. Cisco routers automatically create an IPv6 link-local address whenever a global unicast address is assigned to the interface. By default, Cisco IOS routers use EUI-64 to generate the Interface ID for all link-local address on IPv6 interfaces. For serial interfaces, the router will use the MAC address of an Ethernet interface. Recall that a link-local address must be unique only on that link or network. However, a drawback to using the dynamically assigned link-local address is its long interface ID, which makes it challenging to identify and remember assigned addresses. MAC address on router R1's GigabitEthernet 0/0 interface. This address is used to dynamically create the link-local address on the same interface. To make it easier to recognize and remember these addresses on routers, it is common to statically configure IPv6 link-local addresses on routers.

Public and Private IPv4 Addresses

Public IPv4 addresses are addresses which are globally routed between ISP (Internet Service Provider) routers. However, not all available IPv4 addresses can be used on the Internet. There are blocks of addresses called private addresses that are used by most organizations to assign IPv4 addresses to internal hosts. In the mid-1990s private IPv4 addresses were introduced because of the depletion of IPv4 address space. Private IPv4 addresses are not unique and can be used by an internal network. Specifically, the private address blocks are: · 10.0.0.0 /8 or 10.0.0.0 to 10.255.255.255 · 172.16.0.0 /12 or 172.16.0.0 to 172.31.255.255 · 192.168.0.0 /16 or 192.168.0.0 to 192.168.255.255 It is important to know that addresses within these address blocks are not allowed on the Internet and must be filtered (discarded) by Internet routers. For example, in the figure, users in networks 1, 2, or 3 are sending packets to remote destinations. The Internet Service Provider (ISP) routers would see that the source IPv4 addresses in the packets are from private addresses and would, therefore, discard the packets. Note: Private addresses are defined in RFC 1918. Most organizations use private IPv4 addresses for their internal hosts. However, these RFC 1918 address are not routable in the Internet and must be translated to a public IPv4 address. Network Address Translation (NAT) is used to translate between private IPv4 and public IPv4 addresses. This is usually done on the router that connects the internal network to the ISP's network. Home routers provide the same capability. For instance, most home routers assign IPv4 addresses to their wired and wireless hosts from the private address of 192.168.1.0 /24. The home router interface that connects to the Internet service provider (ISP) network is assigned a public IPv4 address to use on the Internet.

What is ARP used for?

Short for Address Resolution Protocol, a network layer protocol used to convert an IP address into a physical address (called a DLC address), such as an Ethernet address. ... There is also Reverse ARP (RARP)which can be used by a host to discover its IP address.

IPv6 Network Addresses

The Need for IPv6 IPv6 is designed to be the successor to IPv4. IPv6 has a larger 128-bit address space, providing for 340 undecillion addresses. (That is the number 340, followed by 36 zeroes.) However, IPv6 is more than just larger addresses. When the IETF began its development of a successor to IPv4, it used this opportunity to fix the limitations of IPv4 and include additional enhancements. One example is Internet Control Message Protocol version 6 (ICMPv6), which includes address resolution and address auto-configuration not found in ICMP for IPv4 (ICMPv4). ICMPv4 and ICMPv6 will be discussed later in this chapter. Need for IPv6 The depletion of IPv4 address space has been the motivating factor for moving to IPv6. As Africa, Asia and other areas of the world become more connected to the Internet, there are not enough IPv4 addresses to accommodate this growth. As shown in the figure, four out of the five RIRs have run out of IPv4 addresses. IPv4 has a theoretical maximum of 4.3 billion addresses. Private addresses in combination with Network Address Translation (NAT) have been instrumental in slowing the depletion of IPv4 address space. However, NAT breaks many applications and has limitations that severely impede peer-to-peer communications.

What is ICMP used for?

ICMP (Internet Control Message Protocol) is an error-reporting protocol network devices like routers use to generate error messages to the source IP address when network problems prevent delivery of IP packets. ... Any IP network device has the capability to send, receive or process ICMP messages.

What port is ICMP?

ICMP has no ports and is neither TCP nor UDP. ICMP is IP protocol 1 (see RFC792), TCP is IP protocol 6 (described in RFC793) and UDP is IP protocol 17(see RFC768). UDP and TCP have ports, ICMP has no ports, but types and codes.

What layer is ICMP protocol?

ICMP is categorized as a layer 3 protocol in the OSI model, but as far as i can tell it does not meet the definition of a network layer protocol. It does not provide addressing or packet routing (it uses IP for this), so all it does is send information from one node to another node, like a transport protocol.

EUI-64 Process

IEEE defined the Extended Unique Identifier (EUI) or modified EUI-64 process. This process uses a client's 48-bit Ethernet MAC address, and inserts another 16 bits in the middle of the 48-bit MAC address to create a 64-bit Interface ID. Ethernet MAC addresses are usually represented in hexadecimal and are made up of two parts: · Organizationally Unique Identifier (OUI) - The OUI is a 24-bit (6 hexadecimal digits) vendor code assigned by IEEE. · Device Identifier - The device identifier is a unique 24-bit (6 hexadecimal digits) value within a common OUI.

What is ARP table in switch?

IP addresses to MAC addresses. The tables you refer to aren't quite complete. Layer 2 switches also have two kinds of tables: an ARP table that's used to communicate with the switch "as a computer" for interfacing with its controls. ... a table that relates switch ports to MAC addresses.

IPv4 Issues and Solutions

IPV6 - 128-bit address/340 undecillion addresses. IPv4 - 32 bit address /4.3 billion addresses Tunnelling - transports a IPV6 packet over IPV4 networks Transmission - uses NAT64 to convert between IPV6 and IPV4 Dual Stack - Allows IPv4 and IPv6 to coexist on the same network

Structure of an IPv6 Global Unicast Address

IPv6 global unicast addresses (GUA) are globally unique and routable on the IPv6 Internet. These addresses are equivalent to public IPv4 addresses. The Internet Committee for Assigned Names and Numbers (ICANN), the operator for IANA, allocates IPv6 address blocks to the five RIRs. Currently, only global unicast addresses with the first three bits of 001 or 2000::/3 are being assigned. In other words, the first hexadecimal digit of a GUA address will begin with a 2 or a 3. This is only 1/8th of the total available IPv6 address space, excluding only a very small portion for other types of unicast and multicast addresses. Note: The 2001:0DB8::/32 address has been reserved for documentation purposes, including use in examples. A global unicast address has three parts: · Global routing prefix · Subnet ID · Interface ID

What is subnet mask with example?

If you take a class c network as an example the starting subnet mask is 255.255.255.0. The lower 8 bits you can use for subnetting. if you use 4 bits for the sub network and 4 for hosts you get a subnet mask of. 255.255.255.240. 128+64+32+16=240.

Internet of Everything

The Internet of today is significantly different than the Internet of past decades. The Internet of today is more than email, web pages, and file transfer between computers. The evolving Internet is becoming an Internet of things. No longer will the only devices accessing the Internet be computers, tablets, and smartphones. The sensor-equipped, Internet-ready devices of tomorrow will include everything from automobiles and biomedical devices, to household appliances and natural ecosystems. With an increasing Internet population, a limited IPv4 address space, issues with NAT and an Internet of Everything, the time has come to begin the transition to IPv6.

How do you calculate subnet mask from number of hosts?

, "255.255.255.0," the number "255" is eight ones represented in binary. Using this example there are 24 bits in the network portion of the subnet mask. Subtract the number of network bits from 32 to obtain the number of host bits, then convert the binary number to decimal.

ICMPv4 and ICMPv6

Although IP is only a best-effort protocol, the TCP/IP suite does provide for messages to be sent in the event of certain errors. These messages are sent using the services of ICMP. The purpose of these messages is to provide feedback about issues related to the processing of IP packets under certain conditions, not to make IP reliable. ICMP messages are not required and are often not allowed within a network for security reasons. Although IP is only a best-effort protocol, the TCP/IP suite does provide for messages to be sent in the event of certain errors. These messages are sent using the services of ICMP. The purpose of these messages is to provide feedback about issues related to the processing of IP packets under certain conditions, not to make IP reliable. ICMP messages are not required and are often not allowed within a network for security reasons. ICMP is available for both IPv4 and IPv6. ICMPv4 is the messaging protocol for IPv4. ICMPv6 provides these same services for IPv6 but includes additional functionality. In this course, the term ICMP will be used when referring to both ICMPv4 and ICMPv6. The types of ICMP messages and the reasons why they are sent, are extensive. We will discuss some of the more common messages. ICMP messages common to both ICMPv4 and ICMPv6 include:

What is the difference between network address and host address?

An IP address can be broken down into two parts, namely the Network Address and Host Address. ... The host address can range anywhere between the Network and Broadcast Address, i.e., 172.18.230.121 to 172.18.230.126 . You can arrive at these addresses by performing an logical AND on the IP address and the Subnet Mask.

IPv6 Link-Local Unicast Addresses

An IPv6 link-local address enables a device to communicate with other IPv6-enabled devices on the same link and only on that link (subnet). Packets with a source or destination link-local address cannot be routed beyond the link from which the packet originated. The global unicast address is not a requirement. However, every IPv6-enabled network interface is required to have a link-local address. If a link-local address is not configured manually on an interface, the device will automatically create its own without communicating with a DHCP server. IPv6-enabled hosts create an IPv6 link-local address even if the device has not been assigned a global unicast IPv6 address. This allows IPv6-enabled devices to communicate with other IPv6-enabled devices on the same subnet. This includes communication with the default gateway (router). IPv6 link-local addresses are in the FE80::/10 range. The /10 indicates that the first 10 bits are 1111 1110 10xx xxxx. The first hextet has a range of 1111 1110 1000 0000 (FE80) to 1111 1110 1011 1111 (FEBF). Note: Typically, it is the link-local address of the router, and not the global unicast address, that is used as the default gateway for other devices on the link.

IPv6 Unicast Addresses

An IPv6 unicast address uniquely identifies an interface on an IPv6-enabled device. A packet sent to a unicast address is received by the interface that is assigned that address. Similar to IPv4, a source IPv6 address must be a unicast address. The destination IPv6 address can be either a unicast or a multicast address. The most common types of IPv6 unicast addresses are global unicast addresses (GUA) and link-local unicast addresses.

Unique Local

Another type of unicast address is the unique local unicast address. IPv6 unique local addresses have some similarity to RFC 1918 private addresses for IPv4, but there are significant differences. Unique local addresses are used for local addressing within a site or between a limited number of sites. These addresses should not be routable in the global IPv6 and should not be translated to a global IPv6 address. Unique local addresses are in the range of FC00::/7 to FDFF::/7. With IPv4, private addresses are combined with NAT/PAT to provide a many-to-one translation of private-to-public addresses. This is done because of the limited availability of IPv4 address space. Many sites also use the private nature of RFC 1918 addresses to help secure or hide their network from potential security risks. However, this was never the intended use of these technologies, and the IETF has always recommended that sites take the proper security precautions on their Internet-facing router. Unique local addresses can be used for devices that will never need or have access from another network.

How does subnet mask work?

Applying a Subnet Mask. A subnet mask neither works like an IP address nor does it exist independently of them. Instead, subnet masks accompany an IP address and the two values work together. Applying the subnet mask to an IP address splits the address into two parts, an extended network address, and a host address.

broadcast transmission

Broadcast traffic is used to send packets to all hosts in the network using the broadcast address for the network. With a broadcast, the packet contains a destination IPv4 address with all ones (1s) in the host portion. This means that all hosts on that local network (broadcast domain) will receive and look at the packet. Many network protocols, such as DHCP, use broadcasts. When a host receives a packet sent to the network broadcast address, the host processes the packet as it would a packet addressed to its unicast address. Broadcast may be directed or limited. A directed broadcast is sent to all hosts on a specific network. For example, a host on the 172.16.4.0/24 network sends a packet to 172.16.4.255. A limited broadcast is sent to 255.255.255.255. By default, routers do not forward broadcasts. As an example, a host within the 172.16.4.0/24 network would broadcast to all hosts in its network using a packet with a destination address of 255.255.255.255. When a packet is broadcast, it uses resources on the network and causes every receiving host on the network to process the packet. Therefore, broadcast traffic should be limited so that it does not adversely affect the performance of the network or devices. Because routers separate broadcast domains, subdividing networks can improve network performance by eliminating excessive broadcast traffic.

RA Option 1: SLAAC

By default, the RA message suggests that the receiving device use the information in the RA message to create its own IPv6 global unicast address and for all other information. The services of a DHCPv6 server are not required. SLAAC is stateless, which means there is no central server (for example, a stateful DHCPv6 server) allocating global unicast addresses and keeping a list of devices and their addresses. With SLAAC, the client device uses the information in the RA message to create its own global unicast address. As the two parts of the address are created as follows: · Prefix - Received in the RA message · Interface ID - Uses the EUI-64 process or by generating a random 64-bit number Dynamic Configuration - DHCPv6 By default, the RA message is option 1, SLAAC only. The router's interface can be configured to send a router advertisement using SLAAC and stateless DHCPv6, or stateful DHCPv6 only.

How do you calculate the number of hosts?

Calculating the maximum possible number of hosts in a subnet: To find the maximum number of hosts, look at the number of binary bits in the host number above. The easiest way to do this is to subtract the netmask length from 32 (number of bits in an IPv4 address).

What is classless subnetting?

Classful Networks were replaced by Classless Subnets across all Public Routers using a Classless Subnet Masks instead of Classful default Network Masks to save the IP Space. Prefix by CIDR. Classless Inter Domain Routing (CIDR) introduced what is called prefix.

What is Classful and classless IP address?

Classful and Classless Routing. ... Classless addressing uses a two-part view of IP addresses, and classful addressing has a three-part view. With classful addressing, the address always has an 8-, 16-, or 24-bit network field, based on the Class A, B, and C addressing rules

What is classless and classful routing?

Classless routing protocols do send the subnet mask with their updates. Thus, Variable Length Subnet Masks (VLSMs) are allowed when using classless routing protocols. Examples of classful routing protocols include RIPv1 and IGRP. Examples of classless routing protocols include RIPv2, EIGRP, OSPF, and IS-IS.

What is the range for link local addresses?

Close, the range for IPv4 is 169.254.0.0/16 (169.254.0.1 to 169.254.255.254), with 169.254.0.0 and 169.254.255.255 reserved as network/broadcast addresses. IPv6 has fe80::/10 reserved for Link-Local addresses with most automatically assigned ones being in the fe80::/64 range.

Static Link-Local Addresses

Configuring the link-local address manually provides the ability to create an address that is recognizable and easier to remember. Typically, it is only necessary to create recognizable link-local addresses on routers. This is beneficial because router link-local addresses are used as default gateway addresses and in routing advertisement messages. Link-local addresses can be configured manually using the same interface command used to create IPv6 global unicast addresses but with the additional link-local parameter. When an address begins with this hextet within the range of FE80 to FEBF, the link-local parameter must follow the address. The figure shows the configuration of a link-local address using the ipv6 address interface command. The link-local address FE80::1 is used to make it easily recognizable as belonging to router R1. The same IPv6 link-local address is configured on all of R1's interfaces. FE80::1 can be configured on each link because it only has to be unique on that link. Similar to R1, router R2 would be configured with FE80::2 as the IPv6 link-local address on all of its interfaces.

How do I find network prefix length?

Expressing network addresses and host addresses with the dotted decimal subnet mask address can become cumbersome. Fortunately, there is an alternate shorthand method of identifying a subnet mask called the prefix length. Specifically, the prefix length is the number of bits set to 1 in the subnet mask. It is written in "slash notation", which is a "/" followed by the number of bits set to 1. Therefore, count the number of bits in the subnet mask and prepend it with a slash. The first column lists various subnet masks that can be used with a host address. The second column displays the converted 32-bit binary address. The last column displays the resulting prefix length.

Types of IPv6 addresses

Global Unicast Unice, internet-rotatable IPv6 address (Dynamic or static) 2001:db8:ACAB::1/64 Link Local FE80::1 Used to communicate other devices on the same IPv6 subnet. /64 Typical IPv6 prefix used to indicate the network portion of the address

Legacy Classful Addressing

In 1981, Internet IPv4 addresses were assigned using classful addressing as defined in RFC 790, Assigned Numbers. Customers were allocated a network address based on one of three classes, A, B, or C. The RFC divided the unicast ranges into specific classes called: · Class A (0.0.0.0/8 to 127.0.0.0/8) - Designed to support extremely large networks with more than 16 million host addresses. It used a fixed /8 prefix with the first octet to indicate the network address and the remaining three octets for host addresses. All class A addresses required that the most significant bit of the high-order octet be a zero creating a total of 128 possible class A networks. Figure 1 summarizes the class A. · Class B (128.0.0.0 /16 - 191.255.0.0 /16) - Designed to support the needs of moderate to large size networks with up to approximately 65,000 host addresses. It used a fixed /16 prefix with the two high-order octets to indicate the network address and the remaining two octets for host addresses. The most significant two bits of the high-order octet must be 10 creating over 16,000 networks. Figure 2 summarizes the class B. · Class C (192.0.0.0 /24 - 223.255.255.0 /24) - Designed to support small networks with a maximum of 254 hosts. It used a fixed /24 prefix with the first three octets to indicate the network and the remaining octet for the host addresses. The most significant three bits of the high-order octet must be 110 creating over 2 million possible networks. Figure 3 summarizes the class C. Note: There is also a Class D multicast block consisting of 224.0.0.0 to 239.0.0.0 and a Class E experimental address block consisting of 240.0.0.0 - 255.0.0.0.

What is the main purpose of ARP?

In an Ethernet local area network, however, addresses for attached devices are 48 bits long. (The physical machine address is also known as a Media Access Control or MAC address.) A table, usually called the ARP cache, is used to maintain a correlation between each MAC address and its corresponding IP address.

What does IP address 0.0 0.0 mean?

In the context of a route entry, it usually means the default route. ... In the context of servers, 0.0.0.0 means "all IPv4 addresses on the local machine". If a host has two ip addresses, 192.168.1.1 and 10.1.2.1, and a server running on the host listens on 0.0.0.0, it will be reachable at both of those IPs

How ICMP messages are encapsulated?

Internet Control Message Protocol (ICMP) and other layer 3 protocols. ICMP is actually a user of the IP protocol--in other words, ICMP messages must be encapsulated within IP packets. ... A ping command sends an ICMP echo request to the target host.

What is the ARP process?

It starts with the initiator sending an ARP Request as a broadcast frame to the entire network. This request must be a broadcast, because at this point the initiator does not know the target's MAC address, and is therefore unable to send a unicast frame to the target. Since it was a broadcast, all nodes on the network will receive the ARP Request. All nodes will take a look at the content of the ARP request to determine whether they are the intended target. The nodes which are not the intended target will silently discard the packet. The node which is the target of the ARP Request will then send an ARP Response back to the original sender. Since the target knows who sent the initial ARP Request, it is able to send the ARP Response unicast, directly back to the initiator.

How do I find my subnet address?

Let's use IP address 192.168.10.44 with subnet mask 255.255.255.248 or /29. STEP 1: Convert to Binary. STEP 2: Calculate the Subnet Address. ... STEP 3: Find Host Range. ... STEP 4: Calculate the Total Number of Subnets and Hosts Per Subnet.

Why is Subnet Mask 255?

Like IPv4 addresses, an IPv4 subnet mask contains four bytes (32 bits) and is written using the same dotted-decimal quadrant notation. In this method, the series of 8 binary 1s is translated to the decimal number 255. For example, a common IPv4 address is 192.168.1.1 with a subnet mask of 255.255.255.0.

Link-local

Link-local addresses are used to communicate with other devices on the same local link. With IPv6, the term link refers to a subnet. Link-local addresses are confined to a single link. Their uniqueness must only be confirmed on that link because they are not routable beyond the link. In other words, routers will not forward packets with a link-local source or destination address.

Host Configuration

Manually configuring the IPv6 address on a host is similar to configuring an IPv4 address. the default gateway address configured for PC1 is 2001:DB8:ACAD:1::1. This is the global unicast address of the R1 GigabitEthernet interface on the same network. Alternatively, the default gateway address can be configured to match the link-local address of the GigabitEthernet interface. Either configuration will work. Just as with IPv4, configuring static addresses on clients does not scale to larger environments. For this reason, most network administrators in an IPv6 network will enable dynamic assignment of IPv6 addresses. There are two ways in which a device can obtain an IPv6 global unicast address automatically: · Stateless Address Autoconfiguration (SLAAC) · Stateful DHCPv6 Note: When DHCPv6 or SLAAC is used, the local router's link-local address will automatically be specified as the default gateway address.

RA Option 3: Stateful DHCPv6

Stateful DHCPv6 is similar to DHCP for IPv4. A device can automatically receive its addressing information including a global unicast address, prefix length, and the addresses of DNS servers using the services of a stateful DHCPv6 server. With this option the RA message suggests devices use: · The router's link-local address, the RA's source IPv6 address for the default gateway address. · A stateful DHCPv6 server to obtain a global unicast address, DNS server address, domain name and all other information. A stateful DHCPv6 server allocates and maintains a list of which device receives which IPv6 address. DHCP for IPv4 is stateful. Note: The default gateway address can only be obtained dynamically from the RA message. The stateless or stateful DHCPv6 server does not provide the default gateway address.

Dynamic Configuration - SLAAC

Stateless Address Autoconfiguration (SLAAC) is a method that allows a device to obtain its prefix, prefix length, default gateway address, and other information from an IPv6 routerwithout the use of a DHCPv6 server. Using SLAAC, devices rely on the local router's ICMPv6 Router Advertisement (RA) messages to obtain the necessary information. IPv6 routers periodically send out ICMPv6 RA messages, every 200 seconds, to all IPv6-enabled devices on the network. An RA message will also be sent in response to a host sending an ICMPv6 Router Solicitation (RS) message. IPv6 routing is not enabled by default. To enable a router as an IPv6 router, the ipv6 unicast-routing global configuration command must be used. Note: IPv6 addresses can be configured on a router without it being an IPv6 router. The ICMPv6 RA message is a suggestion to a device on how to obtain an IPv6 global unicast address. The ultimate decision is up to the device's operating system. The ICMPv6 RA message includes: · Network prefix and prefix length - Tells the device which network it belongs to. · Default gateway address - This is an IPv6 link-local address, the source IPv6 address of the RA message. · DNS addresses and domain name - Addresses of DNS servers and a domain name.

Why do we need subnet mask?

Subnet mask can be used to find if an IP address is present on a subnet or not. - Subnet mask is utilized for isolating the network id and host ids. - This is to reduce the broadcast domain or to reduce heavy network traffic. - A subnet mask helps in separating an IP address into network and host address.

What is host address and network address?

The 255 address (in binary notation, a host address of all ones) is used to broadcast a message to every host on a network. Just remember that the first and last address in any network or subnet cannot be assigned to any individual host. ... The subnet mask 255.255.255.192 gives you four networks of 62 hosts each.

What is the host address in IP address?

The 255 address (in binary notation, a host address of all ones) is used to broadcast a message to every host on a network. Just remember that the first and last address in any network or subnet cannot be assigned to any individual host. You should now be able to give IP addresses to 254 hosts.

Why is ARP important?

The Address Resolution Protocol (or ARP) is a very important part of IP networking. ... For most of us, that means that ARP is used to link our IP addressing to our Ethernet addressing (MAC Addressing). For you to communicate with any device on your network, you must have the Ethernet MAC address for that device.

Which utility uses the Internet Control Messaging Protocol ICMP )?

The Internet Control Message Protocol is an internet layer protocol used by network devices to diagnose network communication issues. ICMP is mainly used to determine whether or not data is reaching its intended destination in a timely manner. Commonly, the ICMP protocol is used on network devices, such as routers.

What is the Internet of Everything definition?

The internet of everything (IoE) is a broad term that refers to devices and consumer products connected to the internet and outfitted with expanded digital features. It is a philosophy in which technology's future is comprised of many different types of appliances, devices and items connected to the global internet.

What is an ICMP attack?

The Smurf attack is a distributed denial-of-service attack in which large numbers of Internet Control Message Protocol (ICMP) packets with the intended victim's spoofed source IP are broadcast to a computer network using an IP broadcast address.

Subnet ID

The Subnet ID is used by an organization to identify subnets within its site. The larger the subnet ID, the more subnets available.

ICMPv6 Router Solicitation and Router Advertisement Messages

The informational and error messages found in ICMPv6 are very similar to the control and error messages implemented by ICMPv4. However, ICMPv6 has new features and improved functionality not found in ICMPv4. ICMPv6 messages are encapsulated in IPv6. ICMPv6 includes four new protocols as part of the Neighbor Discovery Protocol (ND or NDP). Messaging between an IPv6 router and an IPv6 device: · Router Solicitation (RS) message · Router Advertisement (RA) message Messaging between IPv6 devices: · Neighbor Solicitation (NS) message · Neighbor Advertisement (NA) message Note: ICMPv6 ND also includes the redirect message, which has a similar function to the redirect message used in ICMPv4.

What is the use of network ID and broadcast ID?

The network ID is used by routers so they have some thing like any address belong to 192.168.1.0/24 network send it over to this router. The Broadcast ID is used by nodes as the destination address when they want to send a broadcast like Arp requestes.

What is network and host portion in an IP address?

The octet in the subnet mask containing 224 has three consecutive binary 1s in it: 11100000 . Therefore the "network portion" of the whole IP address is: 192.168.32.0 . The "host portion" of the ip address is 0.0.1.22 . Using your notation, the third octet of ip 192.168.33.22 (mask 255.255.224.0) is: 001.

What are link local addresses used for?

The purpose of this document is to provide an understanding of IPv6 Link-local address in a network. A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format.

Verifying IPv6 Address Configuration

The show interface command displays the MAC address of the Ethernet interfaces. EUI-64 uses this MAC address to generate the Interface ID for the link-local address. Additionally, the show ipv6 interface brief command displays abbreviated output for each of the interfaces. The [up/up] output on the same line as the interface indicates the Layer 1/Layer 2 interface state. This is the same as the Status and Protocol columns in the equivalent IPv4 command. Notice that each interface has two IPv6 addresses. The second address for each interface is the global unicast address that was configured. The first address, the one that begins with FE80, is the link-local unicast address for the interface. Recall that the link-local address is automatically added to the interface when a global unicast address is assigned. Also, notice that R1's Serial 0/0/0 link-local address is the same as its GigabitEthernet 0/0 interface. Serial interfaces do not have Ethernet MAC addresses, so Cisco IOS uses the MAC address of the first available Ethernet interface. This is possible because link-local interfaces only have to be unique on that link. The link-local address of the router interface is typically the default gateway address for devices on that link or network. the show ipv6 routecommand can be used to verify that IPv6 networks and specific IPv6 interface addresses have been installed in the IPv6 routing table. The show ipv6 route command will only display IPv6 networks, not IPv4 networks. Within the route table, a C next to a route indicates that this is a directly connected network. When the router interface is configured with a global unicast address and is in the "up/up" state, the IPv6 prefix and prefix length is added to the IPv6 routing table as a connected route. Note: The L indicates a Local route, the specific IPv6 address assigned to the interface. This is not a link-local address. Link-local addresses are not included in the router's routing table because they are not routable addresses. The IPv6 global unicast address configured on the interface is also installed in the routing table as a local route. The local route has a /128 prefix. Local routes are used by the routing table to efficiently process packets with a destination address of the router's interface address. The ping command for IPv6 is identical to the command used with IPv4, except that an IPv6 address is used. the command is used to verify Layer 3 connectivity between R1 and PC1. When pinging a link-local address from a router, Cisco IOS will prompt the user for the exit interface. Because the destination link-local address can be on one or more of its links or networks, the router needs to know which interface to send the ping to. Use the Syntax Checker to verify IPv6 address configuration. Note: The L indicates a Local route, the specific IPv6 address assigned to the interface. This is not a link-local address. Link-local addresses are not included in the router's routing table because they are not routable addresses.

What is the purpose of subnet mask?

The subnet mask is used by the TCP/IP protocol to determine whether a host is on the local subnet or on a remote network. So now you know, for this example using a 255.255.255.0 subnet mask, that the network ID is 192.168.123.0, and the host address is 0.0.0.132.

Do switches ARP?

The switch does not perform the ARP broadcast. If the destination MAC address is not in the switches MAC address table, the switch simply floods the frame out all ports except the port it was received on. The switch will ARP only if the ping is initiated from the switch.

Special User IPv4 Addresses

There are certain addresses such as the network address and broadcast address that cannot be assigned to hosts. There are also special addresses that can be assigned to hosts, but with restrictions on how those hosts can interact within the network. · Loopback addresses (127.0.0.0 /8 or 127.0.0.1 to 127.255.255.254) - More commonly identified as only 127.0.0.1, these are special addresses used by a host to direct traffic to itself. For example, it can be used on a host to test if the TCP/IP configuration is operational, such as shown in the figure. Notice how the 127.0.0.1 loopback address replies to the ping command. Also note how any address within this block will loop back to the local host, such as shown with the second ping in the figure. · Link-Local addresses (169.254.0.0 /16 or 169.254.0.1 to 169.254.255.254) - More commonly known as the Automatic Private IP Addressing (APIPA) addresses, they are used by a Windows DHCP client to self-configure in the event that there are no DHCP servers available.Useful in a peer-to-peer connection. · TEST-NET addresses (192.0.2.0/24 or 192.0.2.0 to 192.0.2.255) - These addresses are set aside for teaching and learning purposes and can be used in documentation and network examples. Note: There are also Experimental Addresses in the block 240.0.0.0 to 255.255.255.254 that are reserved for future use (RFC 3330).

IPv6 Address Types

There are three types of IPv6 addresses: · Unicast - An IPv6 unicast address uniquely identifies an interface on an IPv6-enabled device. a source IPv6 address must be a unicast address. · Multicast - An IPv6 multicast address is used to send a single IPv6 packet to multiple destinations. · Anycast - An IPv6 anycast address is any IPv6 unicast address that can be assigned to multiple devices. A packet sent to an anycast address is routed to the nearest device having that address. Anycast addresses are beyond the scope of this course. Unlike IPv4, IPv6 does not have a broadcast address. However, there is an IPv6 all-nodes multicast address that essentially gives the same result.

Interface ID

This is the individual host IP portion. It can be assigned to one interface or more than one interface, depending on the type of IPv6 address.

How do I find my host bit?

To find the maximum number of hosts, look at the number of binary bits in the host number above. The easiest way to do this is to subtract the netmask length from 32 (number of bits in an IPv4 address). This gives you the number of host bits in the address.

What is a characteristic of a link local address?

n a computer network, a link-local address is a network address that is valid only for communications within the network segment (link) or the broadcast domain that the host is connected to. Link-local addresses are not guaranteed to be unique beyond a single network segment.

How does address resolution protocol work?

resolution protocol is a protocol used to match an IP address with its corresponding MAC. ... IP address is a device's address allows. the device to transport packets from a network to network via routers an. IP address cannot be used transport data within the network like.