slides18 Flashcards
how does traceroute work
It sends a packet to the intended destination, but with an artificially small time-to-live
Find out why using UDP is better
UDP packets requires no special privileges
Neighbor Solicitation and Advertisement
Neighbor Solicitation (Type 135)
Neighbor solicitations are used by nodes to determine the link layer address of a neighbor, or to verify that a neighbor is still reachable via a cached link layer address.
Neighbor Advertisement (Type 136)
Neighbor advertisements are used by nodes to respond to a Neighbor Solicitation message.
Stateless Address Autoconfiguration
The stateless mechanism enables a host to generate its own addresses.
EUI-64 method
The EUI-64 method works in collaboration with IPv6 addresses. It is used to derive the host portion (/64) of the IP addresses from the interface MAC address by inserting FFFE in the middle (to go from 48 to 64 bits) and inverting the 7th most significant bit in the MAC address.
documentation reservation in IPv6
To reduce the likelihood of conflict and confusion when relating documented examples to deployed systems, an IPv6 unicast address prefix is reserved for use in examples in RFCs, books, documentation, and the like. Since site-local and link-local unicast addresses have special meaning in IPv6, these addresses cannot be used in many example situations. The document describes the use of the IPv6 address prefix 2001:DB8::/32 as a reserved prefix for use in documentation. This memo provides information for the Internet community.
unique local addresses
A unique local address (ULA) is an Internet Protocol version 6 (IPv6) address in the address range fc00::/7.[1] Its purpose in IPv6 is analogous to IPv4 addressing in private networks. Unique local addresses may be used freely, without centralized registration, inside a single site or organization or spanning a limited number of sites or organizations. They are routable only within the scope of such private networks, but not in the global IPv6 Internet.
criteria for routing (why choose a certain route)
• The smallest number of hops • The fastest: some links might be faster than others, e.g., undersea cable vs. satellite • The cheapest: transit is not free! • The most reliable • And so on
policy based routing
You may wish to restrict where your traffic passes through
IGP
Local routing within an organisation, requiring an interior
gateway protocol
EGP
Non-local routing between organisations, requiring an
exterior gateway protocol
how do routers use routing table
Use first match from top to bottom in the table, which is sorted longest mask to shortest
routing flags
- U: the interface is up (i.e., working)
- G: the route is to a gateway/router. Otherwise the destination is on the local network
- H: the route is to a host. The destination address is a single host, not a network
- D: this entry was created by an ICMP redirect
- M: this entry was modified by an ICMP redirect
how can ICMP modify tables
if the route initiated by a host can be shortened, ICMP updates his routing table
how is the Internet managed
The Internet is managed as a collection of Autonomous Systems (AS), each administered by a single entity, e.g., a University or company
