1.1-1.2 Explain the purposes and uses of ports and protocols. Flashcards
Explain the purposes and uses of DHCP
An automatic method for allocating IP address, Subnet Mask, Default gateway and DNS server addresses.
A host is configured to use DHCP by specifying in the TCP/IP configuration that it should automatically obtain an IP address.
Explain the purposes and uses of ports DHCP 67, 68
- When a DHCP client initializes, it broadcasts to find a DHCP server.
- This is called a DHCPDISCOVER packet.
All communications are sent using UDP, with the server listening on port 67 and the client on port 68. The DHCP server responds to the client with an IP address and other configuration information, as long as it has an appropriate IP address available.
The IP addressing information is offered for a period of time. This packet is also broadcast and is called a DHCPOFFER. The client may choose to accept the offer using a DHCPREQUEST packet—also broadcast onto the network.
Explain the purposes and uses of SECURE SHELL (SSH)
Secure Shell (SSH)is the principal means of obtaining secure remote access to a UNIXor Linux server. The main uses of SSH are for remote administration and secure file transfer (SFTP).
SSH Port #
An SSH server listens on TCP port 22 bydefault.
Explain how the Simple Authentication and Security Layer (SASL) provides binding in Lightweight Directory Access Protocol Secure (LDAPS).
The client and server negotiate the use of a supported security mechanism.
A routing table is corrupted and causing a packet to loop. The router discards the packet and sends a warning packet to the source host. Consider the types of Internet Control Message Protocol (ICMP) messages to determine what type of message the source host receives.
Time exceeded
A time exceeded message is used when the Time to Live (TTL) of a packet reaches 0. A packet has a maximum TTL of 255, and this value is reduced by one every time the packet crosses a router. A packet looping will eventually result in the TTL reaching 0.
An echo request/reply message is used with the ping utility.
A destination unreachable message indicates that a local host, or a host on a remote network, can not be contacted. This can be caused by a configuration error or by a router not being available.
A redirect message is used if there are multiple routers and a more efficient route can be identified
What protocol is an alternative to the Session Initiation Protocol (SIP)?
H.323 Protocol
Real-time Transport Protocol (RTP)
Common Address Redundancy Protocol (CARP)
Real-time Transport Protocol Control Protocol (RTCP)
H.323 Protocol
H.323 is an alternative session control protocol to the Session Initiation Protocol (SIP). Endpoints, known as terminals, connect to gatekeepers to request services.
The Real-time Transport Protocol (RTP) enables the delivery of a stream of media data via the User Datagram Protocol (UDP), while implementing some of the reliability features usually associated with the Transmission Control Protocol (TCP).
The RTP Control Protocol (RTCP) is used by RTP to monitor the quality of the connection and to provide reports to the endpoints.
The Common Address Redundancy Protocol (CARP) handles Virtual Internet Protocol (VIP) addresses for load balancing.
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A system administrator notices a server cannot access network services. Authentication is also failing. The error is an invalid token message. Which of the following protocols should the system administrator verify early in the troubleshooting process?
Network Time Protocol (NTP)
A server or host that is configured with the incorrect time may not be able to access network services. Authentication, and other security mechanisms will often fail if the time is not synchronized on both communicating devices. The Network Time Protocol (NTP) enables the synchronization of time-dependent applications. Errors are likely to be generic failed or invalid token messages.
A router downloads configuration files over User Datagram Protocol (UDP) port 69. The router does not have access to browse the directory or to delete files. Analyze File Transfer Protocols (FTPs) and determine what protocol the router is using.
Trivial File Transfer Protocol (TFTP)
The Trivial File Transfer Protocol (TFTP) supports reading and writing files, not directory browsing or file deletion.
TFTP is a connectionless protocol that runs over User Datagram Port (UDP) port 69.
A system administrator notices a server cannot access network services. Authentication is also failing. The error is an invalid token message. Which of the following protocols should the system administrator verify early in the troubleshooting process?
The Network Time Protocol (NTP) enables the synchronization of time-dependent applications. A server or host that is configured with the incorrect time may not be able to access network services. Authentication, and other security mechanisms will often fail if the time is not synchronized on both communicating devices. Errors are likely to be generic failed or invalid token messages.
Explain how the Simple Authentication and Security Layer (SASL) provides binding in Lightweight Directory Access Protocol Secure (LDAPS).
The client and server negotiate the use of a supported security mechanism.
Authentication, referred to as binding to the server, can be implemented in several ways for Lightweight Directory Access Protocol Secure (LDAPS). The Simple Authentication and Security Layer (SASL) completes binding by the client and server negotiating the use of a supported security mechanism.
Host A sends a packet to Host B. There is congestion on the network that causes a considerable delay. The source host receives a warning packet after the router discards the packet. Compare the types of Internet Control Message Protocol (ICMP) messages to determine what type of message the source host receives.
Time exceeded
A time exceeded message is used when the Time to Live (TTL) of a packet reaches 0. A packet has a maximum TTL of 255, and this value is reduced by one every time the packet crosses a router. A packet looping will eventually result in the TTL reaching 0.
Which protocol uses Network Level Authentication (NLA) which requires the client to authenticate before a full remote session starts?
Virtual Network Computing (VNC)
Secure Shell (SSH)
Remote Desktop Protocol (RDP)
Telnet
Remote Desktop Protocol (RDP)
Remote Desktop Protocol (RDP) is Microsoft’s protocol for operating remote Graphical User Interface (GUI) connections to a Windows machine. RDP uses Network Level Authentication (NLA) which requires the client to authenticate before a full remote session is started.
Which port will a Domain Name Server (DNS) use for record transfers over 512 bytes?
Transmission Control Protocol (TCP) port 23
Transmission Control Protocol (TCP) port 53
User Datagram Protocol (UDP) port 53
User Datagram Protocol (UDP) 69
User Datagram Protocol (UDP) port 53
A Domain Name Server (DNS) server that needs to allow large record transfers over 512 bytes will be configured to allow connections over Transmission Control Protocol (TCP) port 53.
A Simple Network Management Protocol (SNMP) agent informs the monitor of a port failure. Analyze the functions of an SNMP agent to determine what command the monitor uses for this notification.
Get
Walk
Set
Trap
Trap
The Trap command is used when the agent informs the monitor of a notable event, such as a port failure. The threshold for triggering traps can be set for each value.
