Flashcards in Chapter 8: Routing Deck (45):
Any piece of hardware or software that forwards packets based on their destination IP address.
A list of paths to various networks required by routers.
What two fields of a routing table are used to determine the route needed?
Destination LAN IP and Subnet Mask
What two fields of a routing table tell the router what to do with the packet?
Gateway (for IP of next hop)
Interface (for port to use)
If the network ID is directly connected, then the gateway field of the routing table gets set to _________
IP address of port you're sending to
Command to see your routing table in Linux/OSX
A relative value that defines the cost of using this route. (Lowest routes win)
Network Address Translation (NAT)
A means of translating a system's IP address into another IP address before sending it out to a larger network.
Gives individual systems private IPs, and hides them behind the public IP
Port Address Translation (PAT)
Form of NAT that uses port numbers to map traffic from specific machines in the network.
NAT Translation Table
Special database in a NAT router that stores destination IP addresses and ephemeral source ports from outgoing packets and compares them against returning packets.
Static NAT (SNAT)
Maps a single routable (public) IP address to a single machine, allowing you to access that machine from outside the network.
Preventing the passage of any IP packets through any ports other than the ones prescribed by the system administrator.
Dynamic NAT (DNAT)
Type of NAT in which many computers can share a pool of routable IP addresses that number fewer than the computers.
An entry in a router's routing table that is not updated by any automatic route discovery protocols.
Each time a packet goes through a router
Possible Criteria for Determining a Metric
5) Maximum Transmission Unit (MTU)
6) Shortest Path Bridging (SPB)
7) Administrative Distance
When a packet is too big and it's broken into pieces.
Routing protocols that calculate the total cost to get to a particular network ID and compare that cost to the total cost of all other routes to get to that same network. It chooses the route with the lowest cost.
When routers using distance vector protocols continue sending their routing tables to each other, but the routing tables don't change.
What size of network is distance vector good for?
Smaller networks with less than 10 routers or so.
Routing Information Protocol (RIP)
Distance vector routing protocol that dates from the 1980s
Autonomous System (AS)
One or more networks that are governed by a single dynamic routing protocol, which provides routing for the Internet backbone.
32 bit number displayed as two 16 bit numbers separated by a dot.
Exterior Gateway Protocols (EGP)
The protocols AS's use to communicate with each other
Interior Gateway Protocols (IGP)
The protocols that networks within an AS use to communicate
Border Gateway Protocol (BGP)
-An exterior gateway routing protocol that enables groups of routers to share routing information so that efficient, loop-free routes can be established.
- Hybrid or path vector routing protocol
The routers that handle AS-to-AS routing
A way to simplify routing tables into manageable levels. Basically a tiering system, like a tree.
Type of dynamic routing protocol that announces only changes to routing tables, as opposed to the entire routing tables.
Open Shortest Path First (OSPF)
An interior gateway routing protocol developed for IP networks based on the link state algorithm.
When you first launch OSPF-capable routers, they send out _________ called Hello packets looking for other OSPF routers
Link State Advertisements (LSAs)
What is the routing protocol of choice for most large enterprise networks?
When a new router is sending a lot of LSAs
Formula for hop cost in OSPF
100,000,000/(bandwidth in bps)
A group of logically associated OSPF routers designed to maximize routing efficiency while keeping the amount of broadcast traffic well managed.
Address assigned to routers in an OSPF network to prevent flooding beyond the routers in that particular network.
When you interconnect multiple areas, what is the area id of the backbone?
0 or 0.0.0.0
When a multiprotocol router learns route info using on protocol and announces that info using another routing protocol.
Intermediate System to Intermediate System (IS-IS)
A protocol similar to OSPF, but with support for IPv6 since inception.
Enhanced Interior Gateway Routing Protocol (EIGRP)
Cisco's proprietary hybrid protocol that has elements of both distance vector and link state routing.
A cable used to interface with a Cisco device
Networking devices, such as routers and advanced switches, that must be configured to use.
Network Management Software (NMS)
Tools that enable you to describe, visualize, and configure an entire network.
Basic Router Configuration Process
1) Set up the WAN side
2) Set up the LAN
3) Establish Routes
4) Configure a Dynamic Protocol