Lab 2 questions Flashcards
What is the purpose on an ARP-request?
Its purpose is to find the MAC-address of the destination host from the given IP-address.
What layer is the ARP operating on?
It operates between the second layer (data link layer) and the third layer (network layer)
Does ARP use IP-headers?
No, they have their own ARP-header.
When a packet needs to be transmitted to a host on another subnet, what IP address will be
used in the destination field of the IP header?
The IP-address of the host on the other subnet
When a packet needs to be transmitted to a host on another subnet, what MAC address will
be used in the destination field of the MAC header?
The MAC address used will be the MAC address of the router which will transfer it to the subnet.
What MAC destination address is an ARP request ALWAYS sent to?
It gets sent to the broadcast MAC address
What MAC destination address is an ARP reply sent to?
It gets sent to address of the destination which matches the MAC address of the original ARP request.
Exactly what information does an ARP request contain?
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Hardware type (HTYPE)
- the network link protocol type, eg Ethernet.
Protocol type (PTYPE)
This field specifies the internetwork protocol for which the ARP request is intended. For IPv4, this has the value 0x0800. The permitted PTYPE values share a numbering space with those for EtherType.
Hardware length (HLEN)
Length (in octets) of a hardware address. Ethernet address length is 6.
Protocol length (PLEN)
Length (in octets) of internetwork addresses. The internetwork protocol is specified in PTYPE. Example: IPv4 address length is 4.
Operation
Specifies the operation that the sender is performing: 1 for request, 2 for reply.
Sender hardware address (SHA)
Media address of the sender. In an ARP request this field is used to indicate the address of the host sending the request. In an ARP reply this field is used to indicate the address of the host that the request was looking for.
Sender protocol address (SPA)
Internetwork address of the sender.
Target hardware address (THA)
Media address of the intended receiver. In an ARP request this field is ignored. In an ARP reply this field is used to indicate the address of the host that originated the ARP request.
Target protocol address (TPA)
Internetwork address of the intended receiver.
Exactly what information does an ARP reply contain?
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The MAC-address for the destination and its IP-addresses.
What is the purpose of a DNS request?
A Domain name system request is used to obtain information from a DNS-server sent from a user’s computer (DNS-client). Most often the request is about the IP-address associated with a domain name.
When a DNS request is sent to a DNS server on another subnet, what IP destination address
will be used in the IP header?
The IP destination address used will be the IP for the DNS server on the other subnet server.
When a DNS reply is sent by a DNS server to a host on another subnet, what IP destination
address will be used in the IP header?
The IP destination address used will be the IP of the host on the other subnet.
When a DNS reply is sent by a DNS server to a host on another subnet, what MAC
destination address will be used in the MAC header?
The MAC destination address used in the MAC header will be the MAC-address of the router connecting the subnets.
What is the difference between a hub, a switch and a router?
A hub is used to recieve all transmitting signals and then broadcasts it to everyone.
A switch recieves a signal and reroutes it to the correct route.
A router is used to connect different networks together. (Operates on the network layer)
When a switch relays a packet, how will the destination MAC address be affected?
It should not be affected.
