Flashcards
Module 10
Flashcards do conjunto (30)
- 1IP Addressing in Ethernet networks?Need to ensure that every system that needs to communicate has an address and that the address is unique. Two systems cant have the address, else they won't be able to communicate. Easy to manually configure in smaller environments(e.g. 24 systems - quick and can record which device was using which address to avoid duplicates).
However, it is a bad method for large environments(thousands of systems), being prone to errors in configuration, time-consuming and those ending up with the same address configuration would not be able to communicate. - 2EXPLAIN DYNAMIC VS STATIC IP ADDRESS?The approach to fix this is the Dynamic Vs Static IP Addresses. The general approach is the dynamically assigned address(assigned automatically by some kind of entity or process(device requests address and some service responds - dynamic address can change at any time)
Static Address is something you manually configure in most cases and it doesn't change until you change it. Systems on the internet(web/DNS server) need to be contacted usually using the same address, so statically configured.
Can set up so certain systems dynamically or statically receive their address configuration. Usually, clients systems that receive dynamic addresses, and systems such as servers statically configured - 3EXPLAIN DYNAMIC HOST CONFIGURATION PROTOCOL?With automatic configuration(the dynamic addresses), there is a service called Dynamic Host Configuration Protocol or DHCP(a very common service, almost all internal networking environments will use this to handle the large numbers of clients that need addresses).
DHCP PROCESS:
DHCP discover - When a client is configured to obtain an address automatically when device boots it issues out a search for some DHCP service somewhere on the network
DHCP server - In most cases, it is a DHCP server that has this service installed(devices such as routers can also supply DHCP services). so something responds that they have a DHCP service installed.
DHCP scope, subnet mask, options - Once you have a DHCP service, what you configure is a scope(a pool of addresses which client can draw their configurations - typically includes IP address, subnet mask & other options(DNS sever & default gateway they should use)
DHCP reservation - allows a client to still receive its configuration automatically, but they get the same address every time
DHCP lease - Time duration for how long address is valid. - 4EXPLAIN AUTOMATIC PRIVATE IP ADDRESSING?Another option for using DHCP that you may consider to be a bit of a fail-safe. If you have a DHCP server, then it's the system that is responsible for allocating those addresses. Like any other server, it can go down, so if clients are requesting addresses from the server and the server is down, no address is returned.
Rather than no address, the client will initialize itself automatically with a private IP address(AUTOMATIC PRIVATE IP ADDRESS(APIPA). This returned address is always in the format of 169.254.something.something, first 2 values indicate the network, and all systems that initialize using APIPA will use 169.254 - can only communicate with other systems that were also unable to get an address, so may still be able to communicate within your LAN.
More useful as a diagnostic tool though as when you see that address, you know there is a problem with DHCP and can investigate accordingly. - 5EXPLAIN LINK LOCAL ADDRESS?Link Local Address - more of a category than any kind of address assignment. It refers to all of the addresses that are able to see each other within the same subnet or the same local area network(printer, etc) without having to be routed to a different network. So even if the router went down, all systems within that network could still communicate with each other as they'd all be plugged into the same switch(so all using the same network address and can all communicate with each other without having to be routed.
So when you have multiple subnets or multiple networks, all systems within any one subnet are considered to be local addresses with respect to each other
One way or another, you need to make sure that all of the systems that need to communicate have a valid address configuration, whether assigned dynamically or statically is up to you, but ultimately every system must have an address and a unique one too. - 6DEFINE DNS?Domain Name System(DNS) creates a mapping, it says this name equals this IP address. You have to determine the IP address when communicating over TCP/IP. This naming structuring makes things a lot easier for us.
- 7OVERVIEW OF THE DOMAIN NAME SYSTEM?A fully qualified domain name(computer1.courses.skillsoft.com) is broken down into a hierarchy which is essentially the DNS structure. A dot really refers to the route domain. The route is where you can start navigating. So a single database with every single computer mapped to its IP address would be an exceptionally large database. Hence they break it down and spread it across multiple systems, so it's referred to as a distributed database. The hierarchy makes it more manageable. After the route(dot), you see a lot of familiar extensions(.com.gov.net), each section containing some of the names on the internet. Typically see the company name(E.g skillsoft) within this too. Have to find a public registration authority to publically register and gain a domain name. You can do whatever you want with it then such as breaking it down into subdomains(e.g. courses). Any computer within the course's subdomain will have the name of whatever its initial name is(fully qualified domain name).
- 8HOW DNS WORKS?FOWARD DNS LOOKUPS - DNS works through a process known as a forward DNS lookup. meaning as a client you can supply the name but the address is looked up for you.
REVERSE DNS LOOKUPS - can supply the address, the name is looked up for you.
STORE PUBLIC HOST ADDRESS INFORMATION - The DNS database.
DATABASE SERVERS - There are multiple database servers that each contain a portion of the database. Any one server could never maintain the entire structure of every system on the internet. So where you register the domain name(skillsoft.com), you maintain that portion of the database. So all portions across all database servers make up the entire DNS database.
DNS RESOLVER - is the system that's asking for the resolution, so ultimately when you type in that name into your browser, you get an IP address coming back, so you have resolved the name to the IP address.
REQUESTS FEED THROUGH HIERARCHY OF DNS SERVERS - the hierarchy of going through the resolver to the local name server to root server, will forward to (e.g. .com) server, to (skillsoft.com server) to www server. (results are cached) - 9KEY BENEFITS OF DNS?- EASIER TO REMEMBER DOMAIN NAMES(easy to navigate databases and find what we're looking for with a hierarchal approach)
- FLEXIBLE AND EASY TO USE(just need to know the name we're looking for and the service handles the rest)
- CONSISTENT NAMING STRUCTURE(E.g. every system within skillsoft.com will always have that structure and it's always the same)
- SERVER SECURITY(security features to prevent intruders from changing the names or poisoning the databases)
EASILY SCALABLE AND FAULT TOLERANT(as you can export the entire contents of a DNS database to as many other servers as you want, so if one fails, you can have as many other copies to ensure at least one DNS server is able to respond to client requests and handle that name to address resolution) - 10OVERVIEW OF DHCP?DYNAMIC HOST CONFIGURATION PROTOCOL - responsible for automatically assigning the IP address configuration to client systems(includes the subnet mask, default gateway, DNS servers, etc). Essentially an alternative to static configuration.
DHCP automates IP address configuration so clients can: obtain an IP address automatically & obtain DNS server address automatically(For window-based systems you can set it to obtain an IP address automatically while still setting the DNS server address statically) - 11DHCP RESERVATIONS?Can implement Reservations which are
- Permanent IP address assignments(that behave essentially like static address configuration but you can still handle it automatically so you don't have to visit each system and manually enter in the address configuration)
- Used for specific DHCP clients
- Applicable for any DHCP enabled device(does not have to be a Windows operating system, e.g. printer can do it)
- Uses the MAC address(unique value of the target system which you need to know) of the client system to assign the reserved address.
Need to make sure the IP address that you are assigning in the reservation is not part of any other scope or pool, if it is it might get assigned to someone else as well and now you have a duplicate. Hence need to document which addresses your gong to reserve and make sure they are not offered through any other pool. - 12EXPLAIN DHCP SNOOPING AND PREVENTION?The process is broadcast-based so all servers hear the requests, so it's susceptible to what's known as DHCP Snooping(where an intruder can initialize a DHCP server that is unauthorized. so someone can hack into your network, fire up a DHCP server and start handing out invalid addresses to the client systems in an attempt to reroute them so they're divulging sensitive information).
Can prevent this in most environments by implementing an authorized DHCP server which is a trusted response, so if a client sees multiple offers coming in, it can see one's that are trusted or not. Ultimately if an unauthorized server appears on the network, clients can configure to simply disregard those offers, effectively preventing DHCP snooping so only authorized servers are able to assign addresses to their clients.
DHCP Is one of the most common network services, as long as pools are configured correctly & taken security into account; then the client system should receive correct and valid IP address configurations automatically, alleviating a tremendous amount of administrative overhead - 13OVERVIEW BASIC CHARACTERISTICS OF IPv4?THE FOURTH REVISION OF THE INTERNET PROTOCOL
- primary function is to identify the devices on a network(this is how we implement our IP addressing)
- Protocol designed for packet-switched communication networks(the switch/central connection device completes the circuit between your line and the connected one through a virtual circuit to communicate. Once done communicating, it breaks the circuit, so that's packet switching)
- Was the most widely deployed protocol for both internal LAN and internet connectivity - 14Structure of IPv4 Addresses/Binary?Mapping of Integers to Binary Numbers =
Computing only has zero and one, those are the two binary digits or bits that we use when referring to anything in computing. 0 off, 1 on. a number of possible combinations depending on the number of bits, always two, base 2, to the power of however many bits you have. E.g. with 8 bits, you can have 2 to the power of 8 possible combinations which equals 256. The first value counts as zero, the last would be 255.
IP address:
192. 168. 4. 5.
(192)11000000. (168)10101000. (4)00000100. (5)00000101
What happens with TCP/IP IS that each bit has a value. eight bits = one byte. bits 128, 64, 32, 16, 8, 4, 2, 1.
192 = 11000000 = 128 & 64
Four sets of eight bits in this, entire address is 32 bits in length or 4 bytes. Each eight-bit section we call an octet - 15DEFINE IPv6?SUCCESSOR TO VERSION 4 - version 5 was skipped over and released 6 as a more robust protocol.
IPv4 = 32-bit address, yielding approximately 4.3 billion addresses(2 to the power of 32), Address space exhausted. Hence version 6.
IPv6 = 128-bit address(larger address space, will never run out of version 6 addresses) which is 3.4 x 10 to the power of 38 addresses possible. Not readily interoperable with version 4, so can have both protocols installed and enabled, but any one communication has to use one or the other. - 16STRUCTURE OF IPv6 ADDRESSES/BINARY?With 128bits you need a more efficient way to express this rather than writing 128 1s and 0s. Entire address is still divided into two parts, the network prefix(part of the address indicates network) & an interface ID(the part that indicates unique interface on the network). It defaults down the middle in V6, 64bits each. Divides into chunks(each is 16bits than 8(V4)). Express 16 more easily(x = 4bits so XXXX in a chunk = 16bits). Has a total of eight chunks of 16bits = 128bits.
To use a single character to represent four bits, we need a different approach, with hexadecimal.
A decimal value of 0 through 9 still only uses a single character, a decimal value of 10 & above is 2 characters, so hexadecimal once we pass 9, instead of 10, we use A(15=F).
Hexadecimal address = 2001:0DB8;AC10:FE01:0000:0000:0000:0000
2(0010)0(0000)0(0000)1(0001):0(0000)D(1101)B(1011)8(1000): ETC
Full address: 2002:0cc0:0000:0000:0000:0000:00b0:0001
Omit leading zeros(block 4 characters with 0s): 2002:cc0:0:0:0:0:b0:1
Abbreviate groups of zeros: 2002:cc0::b0:1
::=4 0s - can only omit repeating zeros 1 time - 17OVERVIEW OF SUBNET MASK?Is a key component of IP address configurations as you cannot effectively use an IP address without a subnet mask. Every IP address is composed of two sections(Network and Host address).
Within the Host address, there are a certain number of bits available to address your hosts, the value can change but in certain cases, there can be a lot of them(large network). If there are a lot of them, it may make more sense to take that single large network and subdivide it up into multiple smaller units which generates a subnet address out of the host address portion. Then you still end up with a host address but ultimately the subnet mask can be used to make larger networks into smaller networks - 18KEY FEATURES OF A SUBNET MASK?SUB-DIVIDES A LARGE NETWORK INTO SMALLER NETWORKS(if too many hosts are on that network, they can cause a lot of traffic(congestion) and can simply be difficult to manage - so makes more sense to subdivide them into smaller networks with fewer host systems)
SUBNET MASK IS A 32-BIT NUMBER THAT MASKS PORTIONS OF THE HOST IP ADDRESS(this makes it believe there are fewer bits available to address the host systems, so fewer bits = fewer number hosts
NETWORK BITS SET TO 1(values of the subnet mask are still 1-0, 1 indicates the network portion)
HOST BITS SET TO 0(0 indicates the host portion - subnet masks are always just consecutive 1's, then consecutive 0's. e.g. never see 100111011010) - 19EXPLAIN PRIVATE ADDRESSES?In TCP/IP, any given network can be of any given size, but there are some default sizes and they refer to them as class A, B & C. The range of addresses is set, so if your address is anywhere between 10.0.0.0 and 10.255.255.255, you are using a class A address. Likewise, class B begins at 172.16.0.0 - 172.31.255.255. And class C at 192.168.0.0 - 192.168.255.255.
Your own home network/your own regular internet service at home probably uses a 192.168 address or a class C. Referred to as private addresses because we can all use them on the inside of our routers, can all use the same configurations over and over and over again without needing to worry about duplicating the addresses because my network is isolated from yours by routers. So it doesn't matter if I use 192.168.1.0 as my network and you use the exact same value. Private addresses are never forwarded to the public internet. So this is the solution to the fact that we exhausted the IP version four address space, by allowing us to reuse these same ranges over and over and over again on the insides of our routers. - 20EXPLAIN THE COMMONLY USED SUBNETS?Classes come into play with respect to subnet masks as each one has a default subnet mask that defines the size of the network(bits left).
Class A network = /8(address), 16,777,216(#Hosts), 11111111 00000000 00000000 00000000(Network Binary), 255.0.0.0(Network decimal). (8bits are used to identify the network and 24 are then available to address your hosts, 2 to the power of 24 which is over 16 million(very large network). /8 means there are eights ones in the subnet mask)
Class B = /16(address), 65,534(#Hosts), 11111111 11111111 00000000 00000000(Binary), 255.255.0.0(decimal). (2 to the power of 16 is 65,000, a much smaller network)
Class C = /24, 256, 11111111 11111111 11111111 00000000(Binary), 255.255.255.0(decimal). (2 to the power of 8 is 256, smaller network)
1s & 0s converted to decimal value, all 1s = 255, all 0s = 0, so most subnet masks look like this.
CIDR means you can configure classless Inter-Domain Routing. Class A, B, C are defaults. With CIDR, you can use any number after the / (1-32). e.g. /6, 67,108,864, 11111100 00000000 00000000 00000000, 252.0.0.0 - 21EXPLAIN DEFAULT GATEWAY?Commonly found as a value in an IP configuration, but not a necessary value when it comes to pure functionality(when working with TCP/IP, you need an IP address and a subnet mask, only need a default gateway if you need to communicate with systems on a different network than the one you are on, really another term for a router and routers connect networks together and not individual hosts like the switch). Isolated networks with no connectivity to external networks of any kind do not need a default gateway(e.g. for pure functionality within a LAN, it's not required)
- 22EXPLAIN TRAFFIC FLOW THROUGH A DEFAULT GATEWAY AND THE NEED FOR IT?Traffic flow through a default gateway handles:
- Traffic routing(routing refers to network to network to network, not host to host which is switching)
- Transmit request to internet(default gateway transmits requests to the internet through our ISP
- Routes to other networks(ultimately just route anything to any other network)
- Each interconnected network has a default gateway that allows packets to be forwarded(from network to network)
- Information is relayed to a network and back to the requesting device(where it originated from, based on the IP address of that requesting device, as default gateways know which networks they are connected to. So they can form routes to ensure a packet is delivered and anything sent back is to the original device that created the request)
The need for a Default Gateway is dependent on the scenario. Any kind of internet connectivity for an enterprise network, small home/office, needs a default gateway, as the internet counts as a different network. May also see them in WAN connectivity for an enterprise network, as they may have multiple LANs. - 23OVERVIEW OF VPN?Virtual Private Networks(VPNs) allow you to use a very public medium such as the internet in a private fashion.
- Encrypted connection(implemented between two endpoints over the internet)
- Safely transmit sensitive data(due to encryption)
- Prevent unauthorized eavesdropping
- Enables remote work(is a common implementation of a VPN, as it allows you to work as if you were in the corporate network, gives access to this stuff. - 24TYPES OF VPNs?SITE TO SITE VPN - implemented when you have multiple locations, allowing users to permanently(always on) access resources of both locations(will see compliances on both sides that are configured to connect directly with each other by their IP addresses and with encryption). Acting as an extension to the network but uses the internet as the medium as the two sites could be miles apart.
HOST-TO-SITE VPN - implemented when you may only have a small number of users who require a VPN connection(5/10 people who need VPN access - still have a device or some server acting as a VPN concentrator(single point of access where everyone comes in). But the remote user uses software on their computer to launch the connection, allowing them to establish a connection whenever they want instead of it being open all the time to all users in a specific location.
HOST-TO-HOST VPN - No appliance or concentrator, one system would be the client and another the server(concentrator) as you still use the software. connection accepted by a single system on the other side. Best of all resources on one device - 25DEFINE VLAN?VIRTUAL LOCAL AREA NETWORKS(VLAN) - is something you can set up at the level of a switch. when you want to define separate and distinct subnets that are all plugged into the same physical switch. VLAN switch essentially gives you the ability to define the subnets and separate certain systems from each other even though they're all plugged into the same physical switch.
Normally every system would be able to see every other system, but VLANs switches are able to define these distinct subnets. Can divide them however you see fit. If you still want the subnets to connect to each other, you have to do the same configurations as if they were physically separate from each other with their own dedicated switches(in other words you would have to use a router to connect the separate subnets to each other) - 26WHAT ARE THE VLAN FEATURES?- Allows you to separate physical switch ports into distinct subnets
- So you can segregate functional groups(Sales, Marketing, Accounting)
-Certain VLAN switches offer layer 3 functionality(layer 3 is the network layer where routing happens - allows you to implement a degree of routing between even separate subnets). Allows you to control traffic between the VLANs and Administer security and access(so maybe subnet 1 should be able to communicate with subnet 2 but not subnet 3)
- Can also implement this if it supports a feature known as Network Access Control or NAC, based on authorization and authentication(where the user logs in and are recognized by some kind of identity)
Role-Based VLAN assignment - which automatically assigns you to the appropriate VLAN so if that if the user moves around, NAC recognizes who they are and automatically adjusts the interface assignment so they always end up in the correct VLAN - 27OVERVIEW OF VLAN TRUNKING?VLAN trunking is another feature when configuring VLANs, you may encounter it when you have a single VLAN that spans multiple physical switches.
VLAN TRUNKING OVERVIEW
Tunneled VLAN = You have to get the traffic from switch to switch
802.1Q standard(.1Q) - defined by this standard which is simply the specifications for how to move traffic from physical switch to physical switch while still maintaining which VLAN the traffic belongs to.
VLAN tagging/Native VLAN - a process that makes the identity of the VLAN consistent when moving from physical switches. tagging essentially says this traffic belongs to that VLAN, requiring you to explicitly configure the VLAN identity(usually with numbers). You also can go with Native VLAN(default VLAN), which is simply any traffic that is not otherwise tagged. So if untagged, assumed to be on the native VLAN.
This whole process is implemented by two protocols:
VLAN trunking protocol(VTP) - is a proprietary Cisco protocol(only on cisco devices)
Multiple VLAN registration protocol(MVRP) - a task accomplished on non-cisco devices - 28OVERVIEW OF NAT?Network Address Translation(NAT) - a service that came about effectively due to the fact that we now have public and private IP addresses. It can operate on either the IP address(identifies your computer) or the port number(identifies which specific services are running on that computer. e.g. a web server using the HTTP protocol, that's port number 80, distinguishing that service from some other type of request like SMTP which is port 25) or both.
Can both be handled by the same server, the IP address would be the same but the port number would be different based on the application or the request.
So NAT maps private IP & port to public IP & port(port can be changed if necessary, but is dependent on the application) - 29EXPLAIN NAT FOR PRIVATE ADDRESSES?Problems arise when the source IP address is private, the system that's generating the request, as it's destined for a public internet server. The source address is telling the system on the other end where to return the packets, but the return address from the perspective of the internet-based server cannot be a private address. Routers will not forward private addresses out to the public internet. So need to map that private address to a public.
Every router has two interfaces, one that faces the inside and one that faces the outside. The outside interface does have a valid public IP address that's visible to the rest of the internet. So what NAT does is to translate the (e.g. private) 192.168.2.201 return address into 145.10.231.3. This is what the destination address sees as the return address as the packet crosses the router.
So Network Address Translation can work on either the IP & port or both, but ultimately the destination system on the public internet needs to see a public address as the return address, otherwise, you'll not get anything back. - 30DESTINATION NAT?The method above is typically referred to as Souce Network Address Translation because we're changing the source IP. But there's also Destination Network Address Translation which works in the opposite direction.
- Gives external access to internally hosted services(coming from the internet into the network)
- So can have an External IP and port mapping to specific internal hosts(based on requests I'm making, that request can be sent to a specific internal server that has a private IP address)
- This is also known as port forwarding
- It translates multiple private addresses from a single public address based on the port being used(Requests for a web service(port 80) would be directed to the private address of your web server - Requests for mail service(port 25) would be directed to the private address of your mail server. So private address can be two completely different servers.
Either case, Network Address Translation accepts one value and changes it or remaps it to another value so you can locate the appropriate server the appropriate service.
Informações
- Descrição
- Learning Technology Specialist CompTIA A+ (Core 1) FlashCards sobre Module 10, criado por Chantelle Knight em 02-09-2021.
- Criado por
- Chantelle Knight
- Visualizações
- 1
- Avaliação