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
hop
each time a packet goes through a router
common criteria for metrics
hop count - number of routers packet passes through
bandwidth -
delay - latency
cost -
MTU - Maximum Transmission Unit - largest frame route can handle
distance vector
routing protocols that calculate the total cost to get to a particular network id and compares that cost to all the other routes, then chooses the route with lowest cost
convergence
the updating of the routing tablesfor all the routers has completed
also called steady state
RIP
Routing Information Protocol
- maximum hop count of 15
- sends out update every 30 seconds
- could not use VLSM
- no authentication
RIPv2
Routing Information Protocol v2
- added authentication
- distance vector
- IGP
- supports VLSM and discontiguous subents
Autonomous System
one or more networks that are governed by a single dynamic routing protocol within that AS
- does not use IP addressses,
- uses Autonomous System Number (ASN) assigned by IANA (32 bit)
- communicate using BGP
BGP
Border Gateway Protocol
- hybrid routing protocol
- advertise information passed to them from different AS edge routers
- will ignore bad routes
- policies for limiting which and how other routers may access an ISP
- route aggregation (simplies routing tabls into manageable levels)
- path vector
- used on internet, connects AS’s
Link State Dynamic Routing Protocol
announces and forwards indiviudal route changes as they appeared instead of at intervals
OSPF
Open Shortest Path First
- most commonly used IGP
- designed to work within a single AS
- converges faster & more efficient than RIP
- supports authentication
- shortest path first (prevets loops)
- version 2 for IPv4
- version 3 for IPv6
- link state
How does OSPF work?
- send out “Hello Packets” looking for other OSPF routers
- after two adjacent routers form a neighborship through hello packets, they exchange information about route3rs and networks through LSA packets (Link State Advertisement)
- if a route goes down, quickly recomputes a new route with stores LSAs
- metric is cost (proprontional to bandwidth)
IS-IS
Intermediate System to Intermediate System
- extremely similar to OSPF
- uses areas and send-only updates to routing tables
- works from IPv6 from the start
- standard for ISPs
- link state dynamic routing protocol
EIGRP
Enhance Interior Gateway Protocol
- hybrid protocol
- advanced distace vector protocol
- cisco
RIPv1
Distace vector
IGP
old; only used variable subnets within an ALS
route redistribution
takes routes of one protocol (like RIP) and announces those routes over another protocol (like OSPF)
cisco cable
Rollover or YOST cable
settings to connect to serial port in PUTTY
9600 baud
8 bits data
1 stop bit
no parity
what don’t you do with a new router
plug it into an existing network
NMS
network management software
- an advanced tool to manage multiple devices
Trace a route in Windows CLI
tracert
Trace a route in Mac/Linux
traceroute
do routers use the same type of connection for all routes
no
What technology allows you to share a single public IP address with many computers?
Port address translation
Distance vector routing protocols such as RIP rely on what metric to determine the best route?
hop count
What is area 0 called in OSPF
backbone
