Routing Flashcards
Router
- hardware or software that forwards packets based on their destination IP
- work at the network layer
MLS
Multilayer switch
- works at multiples layers of the OSI modem
how a router works
- packets come to router for handling
- strips off any layer 2 information
- drops ip packet into queue
- inspects each packets ip destination and sends the packet out the correct port
routing table
- tells the router where to send packets
- keeps track of destination ip’s, subnet masks, gateways, and interfaces
routing table destination LAN IP
a defined network id. every id directly connected to one of the routers ports is always listed here
routing table gateway
the ip address for the next hop router (where the packets go)
- if the network id is not directly connected to the router, packets go to gateway
- if no gateway needed, will say 0.0.0.0 or On-link
routing table interface
tells the router which of its ports to use
zero in a routing table
means anything
default route in routing table
tells the router exactly what to do with eveyr incoming packet unless another line in the routing table gives another route
view routing table windows CLI
“route print” or “netstat -r”
view routing table in Linux or Mac OS?
netstat -r
metric
relative value that defines the “cost” of using a route
- router will always use the route with the lowest metric
NAT
network address translation
- replaces the source ip address of a computer with the source ip address from the outside router interface on outgoing packets
SNAT
Static NAT
- maps a single routable (not private) IP address to a single machine
DNAT
Dynamic NAT
- many computers can share a pool of routable IP addresses that number fewer than the computers
dynamic routing protocols
routers ability to update their routes dynamically