Network Layer Flashcards
What are the main network protocols?
IPv4
IPv6
ICMP - Internet Control message protocol (e.g. ping)
IPSEC - Adds authenication datagram to header.
What are the features of IPv6?
128-bit addresses.
Colon-hex format
Leading 0s can be replaced with “::”
How are subnets represented?
CIDR - Classless Inter Domain Routing
What are the 6 address scopes of IPv6?
Loopback Link-Layer (used only on link layer) Multicast Unqiue Local (used within a site) Global Unicast
What replaces ARP and ICMP Routing Advertisement in IPv6?
ICMPv6
Whatare the 5 packet types of ICMPv6?
Router Solicitation Router Advertisment Neighbour Solicitation (ARP equiv) Neigbour Advertisment (ARP reply equiv) Redirect (when 'better' first hop found)
What is router advertisement?
A router sending out its address and other data in reponse to a Router Solicitation or as part of its periodical functionality (every 600 seconds).
What does a Router Advertisement message contain? (3)
Network prefix
Router address
DNS information (optional)
When and why does fragmentation occur in IPv6?
At the client when the packet is greater than the MTU.
What is the MTU?
Maximum Transmission Unit
What are the security issues of IPv6?
Privacy issues when using MAC address (basis) to generate IPv6 addresses.
Sheer number can make scanning less feasible.
Undiscovered flaws.
Transition mechanisms can bypass network security.
Why is the network layer unreliable?
It is connectionless (reliablity dealt with by Transport layer).
What can be done to ease traffic?
Splitting into subnets to reduce global traffic. Using ARP (sending some requests over the link layer only).
What are IPv4 subnets?
Logical division of a network.
Each division is localised behind a router.
What are the special addresses of a subnet?
Subnet Network address: First address
Broadcast address: Last address
Router IP address: First/last available addres
What is CIDR?
Classless Inter Domain Routing
Which subnets size should be allocated for each situation?
Interrouting Links, Home/small business, Site
IRR: /127
Home/Small Business: /56
Site: /48
What does a router do?
Forward IP datagrams to other LANs.
How are loop paths prevented?
Using spanning trees to discard any links that create loops.
What is the default router?
The router on a network that connects that network to the internet.
What are global addresses used for?
Being accessible via the internet.
What are the 2 methods for assigning global addresses for IPv4?
DHCP
NAT - Use one public address.
What are the 2 methods of assigning global addreses for IPv6?
SLAAC - Stateless Address Auto Config : Use network prefix (64) and MAC address (64) based host part.
SIIT - Uses translated IPv4.
What does the Border Gateway Protocol do?
Send packets outside the network.
