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Core Concept Protocols Flashcards

1
Q

First Hop Redundancy

A

Provides redundant gateway services for the LAN.

Is an important part of network failover and disaster recovery

Supported on routers and layer 3 switches

Layer 3 switches share a virtual IP address and a virtual mac address with a standby router

Standby routers picks up the virtual ip and mac address if the active gateway fails

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2
Q

First Hop Redundancy Protocols

A

HSRP Hot Standby Router Protocol
VRRP Virtual Router Redundancy Protocol
GLBP Gateway Load Balancing Protocol
CARP Common Address Redundancy Protocol

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3
Q

HSRP

A

Hot Standby Router Protocol

Allows you to configure two or more routers as standby routers and only a single router as an active router at a time

Establishes a fault tolerant default gateway.

Cisco Proprietary, popular and easy to configure

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4
Q

VRRP

A

Virtual Router Redundancy Protocol

Open Source. Functions similarly to HSRP

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5
Q

GLBP

A

Gateway Load Balancing Protocol

Can present multiple gateways in a single instance and provides load balancing across the gateways

Cisco Propriety

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6
Q

CARP

A

Common Address Redundancy Protocol

Similar to HSRP and VRRP

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7
Q

NAT

A

Network Address Translation

Performed by routers and firewalls

Simplest form, NAT is just a one to one address mapping

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8
Q

Static NAT

A

single specific internet address to a single specific internal address

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9
Q

Dynamic NAT

A

uses a pool of internet addresses to provide to internal devices

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10
Q

PAT

A

Port Address Translation

Tracks the NAT sessions by using random TCP port numbers for each session

Number one use is to translate a group of private addresses into a public address that is routable on the internet

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11
Q

SNAT

A

Source NAT

SNAT is the same as NAT

changes the source address of the packets passing through the router

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12
Q

DNAT

A

Destination NAT

Changes the destination address of the packets passing through the router

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13
Q

Port Forwarding

A

Any traffic arriving on a specific TCP or UDP port will be forwarded to a defined internal host and port

Examples of when to use this, for Web Servers for ports 80 (HTTP) and 443 (HTTPS), for a Mail Server port 25 (SMTP), for an IP camera so it’s not hogging the web port 80

Used to access servers or systems that are behind a firewall

Can restrict allowed network resources for added security

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14
Q

DNS

A

Domain Naming System

Resolves IP (Internet Protocol) addresses based on Fully Qualified Domain Names (FQDN)

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15
Q

FQDN

A

Fully Qualified Domain Name

Identifies the specific server or host at the domain

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16
Q

Root Domain

A

.

Literally a dot, a period whatever you wanna call it. It’s invisible, at the very end of the url, but you can type it and it will bring you to the correct website

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17
Q

Top Level Domain

A

Last part of the website

.com, .gov, .org, .edu

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18
Q

Second Level Domain

A

The name of the website, coming before the top level domain

google.com with google being the second level domain

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19
Q

Host Domain

A

The beginning of the website

www. world wide web
mail. mail.google.com
web. something.com

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20
Q

URL

A

Uniform Resource Locator

Includes the FQDN and protocols such as http, https, and ftp

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21
Q

Public DNS Server

A

Resolves public FQDNs to IP addresses

Free to use DNS server on the public internet

Ex: Google DNS

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22
Q

Private DNS Server

A

Private DNS names are associated with an organization/s private IP Addresses

Not part of the public DNS

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23
Q

Split Horizon DNS

A

Split Brain.

A mechanism for DNS servers to supply different results based on the source

The organization may need the internal DNS lookups for the website to map to an internal private IP address, while DNS lookups from the public internet would map to the public IP address

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24
Q

Forward Lookup Zone

A

Resolves FQDNs to IP Addresses

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25
Reverse Lookup Zone
Resolves IP addresses to FQDNs
26
SOA
Start of Authority Record The authoritative name server for a domain. Only one exists per Forward Lookup Zone
27
NS
Name Server Record Provides for quick FQDN to IP Address resolution At least one NS is specified per Lookup Zone. Can have multiple NS records for secondary servers
28
A Record
Host record Simply and FQDN and an Ipv4 address
29
AAA Record
Host reconrd FQDN and IPv6 address
30
CNAME
Alias Record www.example.com == example.com
31
MX
Mail Exchange Record Used to point to a mail server, needs FQDN and ipv4 address Usually points to an A Record
32
SRV
Service Location Record Defines the location of various servers Not used as much as the rest
33
DDNS
Dynamic DNS Let's you use a dynamically assigned public IP address with a public DNS record
34
DNS
Domain Naming System Resolves FQDNs to IP addresses. Requires static ip addresses
35
SSH
Secure Shell Command line access to routers, switches, firewalls, and servers Encrypted session -- TCP port 22 More secure than Telnet
36
Telnet
Command line access to routers, switches, firewalls, and servers Clear text/plain text -- TCP port 23 Should be disabled for best practice
37
ICMP
Internet Control Message Protocol Allows us to test IP connectivity on the network with things like Ping and Traceroute Echo Reply and Echo Request are part of ICMP
38
FTP
File Transfer Protocol TCP ports 20 and 21 Connection oriented. Retrieves files from an FTP server on the network. Used to transfer files to routers, switches, firewalls, servers, and hosts
39
TFTP
Trivial File Transfer Protocol UDP Port 69 Connectionless. Less Reliable. Retrieves files from an FTP server on the network. Used to transfer files to routers, switches, firewalls, servers, and hosts
40
Command Line Tools
Microsoft uses Command Prompt or PowerShell Mac/Linux uses the Bash Terminal
41
IPCONFIG
Windows Displays the IP address ipconfig/all includes the MAC address as well
42
IFCONFIG
Mac/Linux Displays the IP Address ifconfig -a displays the MAC address as well
43
Ping
Lets us test layer 3 connectivity to a host via ip address
44
arp
command displays our arp cache Can enter static arp entries or delete them as well
45
Tracert
Windows Traceroute -- in Linux Mac Shows us all the hops in a path between the host and the destination ip address Displays all layer 3 hops between the computer and destination can see all router hops
46
Pathping
Windows and Mac/Linux Similar to traceroute but also shows more statics about each hop in the path
47
nslookup
Windows and Mac/Linux Performs a domain name lookup on a host name, finds the ip address of that host name
48
netstat
Windows and Mac/Linux Lets us view all the currently active TCP/UDP sessions on our host
49
nbtstat
Displays information related to Windows NetBIOS Windows Only
50
Remote Desktop Access
Allows for logging into a computer's desktop from a remote location Remote Desktop Protocol Microsoft RDP Remote Desktop Connection (RDP Client) Remote Desktop Server VNC Web-based software - teamviewer
51
VNC
VNC (Virtual network computing) Allows for the same type of service and available for a wide range of operating systems
52
Terminal Emulation Software
Provides an interface for connecting to local consoles ports and SSH or Telnet sessions Ex: Putty
53
Protocol Analyzers
Capture traffic from a network interface card (NIC) and lets us dissect the contents of Frames and Packets Ex: Wireshark
54
Looking Glass Sites
Let us check the routing tables and routes on national and global services providers networks Ex: Troubleshooting connectivity on public internet
55
Troubleshooting
What, Why, How to fix it
56
Troubleshooting Network Layer
Missing route to a specific location, or ip address issues
57
Troubleshooting Physical Layer
Cable of physical connection
58
Troubleshooting Data Link Layer
NIC settings, switchport, speed/duplex mismatch, VLANS
59
Troubleshooting Transport Layer
Firewalls, TCP/UDP ports blocked
60
Troubleshooting Methodology
1-7 points 1. Identify the Problem 2. Establish a Theory of Probable Cause 3. Test the Theory 4. Establish a Resolution Plan + identify Effects 5. Implement the Solution (or Escalate) 6. Verify full system functionality 7. Document all Findings, Actions, and Outcomes
61
1. Identify the Problem
Gather information Duplicate the problem if possible Question Users
62
2. Establish a Theory of Probable Cause
Question the obvious Consider multiple approaches Top to bottom / bottom to top OSI Model Divide and Conquer method may be used in this step
63
3. Test the Theory
Once theory is confirmed determine next steps to resolve the issue If theory is not confirmed, establish a new theory or escalate
64
4. Establish a Resolution Plan + Identify Effects
Identify the possible side effects of the resolution plan
65
5. Implement the Solution (or Escalate)
Implement the solution if you're able to or escalate to someone who can implement
66
6. Verify full system functionality
Double check the system works as expected Take Preventative measures where possible Think: Is there a way we can stop this from happening again?
67
7. Document all Findings, Actions, and Outcomes
If the fix was successful then after documenting the fix you are done If the fix was not successful, escalate
68
Half Split Method
Divide and Conquer Divide the circuit or topology in half and test Continue to divide the failed parts in half until the problem component is identified Troubleshoot the problem component
69
End to End Connectivity issues
Use tracecroute, the divide and conquer method, and check layers 1-3 in OSI
70
Wrong IP configuration/default gateway issue
Check and update ip settings on the host, layer 2 in osi
71
Misconfigured DHCP issue
Check the DHCP server scope settings, OSI layer 3
72
Duplicate IP Address issue
Track down the hosts with the duplicate ip addresses and update the ip settings, osi layer 3
73
Speed and DUplex Mismatch issue
Check the host NIC and or router/switch interface speed duplex. Hard set the speed/duplex to the correct setting. OSI layer 2
74
Wrong VLAN assignment issue
Check the switch port for correct VLAN assignment, osi layer 2 issue
75
Broadcast storms/switching loop
Check the switch logs for MAC address flapping as that is a sign of a loop. Identify the loop source and disconnect it until a proper fix is in place. OSI layer 2 issue
76
Hardware Failure
Replace device, OSI layer 2 or 3 depending on the device
77
Incorrect router interface or interface misconfigured issue
Identify the network or interface having a problem and check the interface IP configuration and cable placement, OSI layer 3
78
Routing loop issue
User traceroute to identify the loop and check the routing tables, static routes and dynamic routes on the routers. OSI layer 3
79
Simultaneous wired and wireless connections issue
The host needs to be connected to either the wired or wireless network, not both at the same time. OSI layers 1-3
80
Missing IP routes issue
Check the routing tables on the routers involved and ensure there is a route, OSI layer 3
81
MTU / MTU Blackhole
Some network nodes may require larger MTU than the standard 1500 Bytes. Make sure the MTU configured on the routers and switches meets the requirements of the hosts/nodes, OSI layer 2. MTU size settings refer to Frame sizes and Frames work at the data link layer
82
NIC Teaming misconfiguration issue
Identify the machine causing the loop and disable NIC teaming in the OC, OSI layer 1 and 2, NICs function at DAta link layer and physical alyers

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