Chapter 8 - Routing Flashcards
Define Router
Any piece of hardware or software that forwards packets based on their destination IP address
How does a router determine the destination
By reading the IP addresses of the packets. Destination doesn’t matter
Define Gateway
The IP address for the next hop router; where the packet should go next.
What does the router do if there is more than one route
Picks the best one. the router with the lowest metric wins
In terms of routing, what does zero mean
Anything, like a wildcard
Why is this route important and translate the route into english: Destination: 0.0.0.0 Subnet Mask: 0.0.0.0 Gateway: 76.30.4.1 Interface: WAN
Any destination with any subnet mask forward it to 76.30.4.1 using my WAN port. This tells the router exactly what to do with every incoming packet unless another line says otherwise
Translate this route into english: Destination: 10.12.14.0 Subnet Mask: 255.255.255.0 Gateway: 0.0.0.0 Interface: LAN
Any packet for the 10.12.14.0/24 Network ID, don’t use a gateway, just ARP is on the LAN interface to get the MAC address and send to recipient
What is the Tier One Backbone
Where you’ll find the routers that make the main connections of the internet
Define Metric
a relative value that defines the ‘cost’ of using this route
What is a general statement to describe the internet
A Whole bunch of big powerful routers connected to lots of other big powerful routers
What is a loopback address
As long as it starts with 127 it will always go to 127.0.0.1
jWhat is the difference between a directed broadcast and a full broadcast
Directed broadcast goes only to the targeted subnet rather than the full broadcast domain
Define NAT
Network Address Translation hides the IP addresses of computers on a LAN but still enable those computers to communicate with the broader internet. The router replaces the source IP with its outside interface address
What is basic NAT
Translating the private or internal IP address to a global IP address on a one to one basis.
Define Port Address Translation (Pat)
Uses port numbers to map traffic from specific machines in the network
Define Static NAT
Maps a single routable IP address to a single machine
Define Dynamic NAT
Enables computers to share a pool of routable IP addresses that number fewer than the computer. Dynamic NAT is also called ‘Pooled NAT’
What is a ‘hop’ defined as
Each time a packet goes through a router
What are the three distinct groups of routing protocols
Distance Vector
Link State
Hybrid
What is the criteria for determining a Metric
Hop count - one way count
Bandwidth
Latency - the issue that distance causes
Cost - route through lower bandwidth has more cost than higher bandwidth
Define Maximum Transmission Unit
Maximum Transmission Unit determines the largest frame a particular technology can handle
Define Fragmentation
When a IP packet is too big for a technology the packet is broken into pieces. This causes slowdowns on the network
Define Shortest Path Bridging
Shortest Path Bridging is a routing metric standard to provide true shortest-path forwarding within mesh topology. Provides fast convergence and improved usage of mesh networks with multiple equal cost paths.
Define Distance Vector
calculate the total cost to get to a particular network ID and compare that cost to the total cost of all the other routes. Routers using this transfer their entire routing table to other routers in WAN
What does ‘convergence’ mean in terms of routing
When routers in a WAN all have the same routing table. This is also refferred to as ‘steady state’
What is the limits of a Pure distance vector routing protocol
With networks with less than 10 routers
Give an outline of Routing Information Protocol 1 ‘(RIPv1)
Routing Information Protocol 1
- Distance Vector
- IGP
- Max hop count = 15
- Updates sent out every 15 seconds
- No authentication
- Only used variable subnets within an AS
Define Variable Length Subnet Masking
Networks connected through the router use different subnet masks
What differences are found in Routing Information Protocol 2
- VLSM added
- Authentication is now built in
- Supports Discontiguous subnets
Define Autonomous System
Autonomous System is one or more networks that are governed by a single dynamic routing protocol within that AS
- Use Special identifier = ASN
- 32 Bit ASN (2 x 16-bit numbers, .)
- Use EGP to communicate with each other
- Use IGP to communicate within ASN
Defiine Border Gateway Protocol
Border Gateway Protocol
Hybrid Protocol; Technically a patch vector routing protocol
- Connects ASs
- Manually Configured
- Advertise info from Edge routers
- Supports policies to limit which and how routers access ISP
- Supports route aggregation
Define Route Aggregation
a way to simplify routing tables into manageable levels
Define Edge Routers
AS to AS router communication
Define Interior Gateway Protocols
Interrior Gateway Protocols; used to communicate within an AS
why are the terms Interior Gateway Protocl and Exterior Gateway Protocol used
They are used by large ISPs to separate their interconnected routers using ASNs from other interconnected networks that are not part of this special group of companies
What are two link state dynamic routing protocols
OSPF - Open Shortest Path First
IS IS - Intermediate System to Intermediate System
What is Open Shortest Path First (OSPF)
Open Shortest Path First
- Link state type
- IGP
- Fast and popular
- Uses area IDs (Backbone = 0)
- Designed to work within a single AS
- Send out LSAs
- Cost based on speed; faster bandwidth is lower cost: 100,000,000/bandwidth in bps
10BaseT link OSPF cost = 100,000,000/10,000,000
=10
- LSAs sent every 30 minutesDefine Link State Advertisements (LSA)
Link State Advertisements, also called ‘hello packets’ in order to fine other OSPF routers. When powered on the first time it starts the process of flooding, sending a large number of LSAs.
How do you cut down on excessive broadcast traffic in OSPF
Routers are grouped into ‘areas’
Central Area = Backbone = Area ID 0
- All traffic between areas go through backbone by using ABRs
Define Area border routers (abr)
Area border routers are used to interconnect areas
Define Intermediate System to Intermediate System (IS IS)
Intermediate System to Intermediate System uses the concept of areas and send-only updates to routing tables.
- Link State type
- Alternative to OSPF
- Has advantage of working with IPv6 from start
- De facto standard for ISPs
- Link state dynamic routing protocol
Define Enhanced Interior Gateway Routing Protocol (EIGRP)
Enhanced Interior Gateway Routing Protocol is used by Cisco only.
- Hybrid type
- AKA Advanced Distance Vector Protocol
Define route redistribution
When a routing table in one protocol is sent over to a different protocol. Helpful when using a mix of equipment.
What is a cisco console cable
A rollover, or Yost cable is used to use the routers console via a terminal emulation program (putty)
What are the basic connection settings for a serial port
9600 Baud
8 data bits
1 stop bit
no parity
What technology is used to share a single public IP adress with many computers
Port Address Translation
What is the traceroute used for
discovering information about the routers between you and the destination address
