Chapter 5

     

"Do I Know This Already?" Quiz

A1:	b
A2:	b
A3:	a, b, c
A4:	a, d
A5:	a, c
A6:	c, d
A7:	b
A8:	a
A9:	d
A10:	a, c
A11:	d
A12:	d
A13:	b
A14:	a, d
A15:	d

Q&A

1:	What is the routing algorithm used in OSPF?
A1:	The Dijkstra algorithm is the routing algorithm used in OSPF.
2:	State one method by which a link-state routing protocol attempts to reduce the network overhead.
A2:	Link-state routing protocols are used in larger networks because the method that they use to update the routing tables requires fewer network resources. Link-state routing protocols attempt to reduce network overhead by: - Using multicast addressing - Sending triggered updates - Sending network summaries infrequently if at all - Using small packets from every router to describe their local connectivity, instead of the entire routing table
3:	What is the purpose of the Dijkstra algorithm?
A3:	This is a routing algorithm that iterates on the length of path to determine a shortest path first tree (SPF tree). It is commonly used in link-state routing protocols to determine which route to use.
4:	Name two link-state IP routing protocols.
A4:	OSPF and IS-IS are two link-state IP routing protocols.
5:	Name the TCP port used by BGP-4.
A5:	TCP port 179 is used by BGP.
6:	State the metric used by OSPF.
A6:	The metric cost can be manually configured to represent anything you want, though Cisco has programmed its systems to use the inverse of bandwidth as the default.
7:	How often does Integrated IS-IS send out new LSAs?
A7:	Integrated IS-IS sends out LSAs every 15 minutes or whenever a change in the network is seen.
8:	State one way that OSPF is an improvement over RIPv1.
A8:	OSPF is an improvement over RIPv1 for large networks because of the following: - It uses bandwidth more efficiently , sending incremental updates. - The updates are not broadcast as in RIPv1 but are directed to multicast addresses 224.0.0.5 and 224.0.0.6. - It propagates changes in the network more quickly, with incremental updates and neighbor relationships. - It is not limited in size by a maximum hop count of 15. - It allows for variation in network size throughout the organization, using VLSM. - It is capable of using the MD5 specification. - The metric can be defined manually, allowing for greater sophistication in the path determination. - It is more responsive to network changes, is flexible in network addressing and design, and scales to a larger size.
9:	State one key attribute of OSPF.
A9:	The key attributes of OSPF include the following: - Maintaining a connection-oriented relationship with other routers on the same physical segment. These are known as adjacent neighbors. - Sending the minimum amount of information in an incremental update when there has been a change in the network. This allows for fast network convergence. - Adding another level of hierarchy to the IP address by designing networks into areas. - Using VLSM and summarization. - Assigning specific functionality to different routers to streamline the process of communication change in the network. - Operating within an organization as an interior routing protocol.
10:	State one key attribute of IS-IS.
A10:	The following are attributes of IS-IS: - Routes CLNP traffic. - Routes IP traffic. - Allows VLSM and summarization. - Uses network design of areas to limit CPU- intensive computation. - Assigns functionality to routers to streamline the communication of network change. Level 1 routers deal with interarea updates, whereas Level 2 routers communicate between areas. - Sends incremental updates to conserve both bandwidth and CPU. - Operates within an autonomous system as an internal routing protocol.
11:	State one key attribute of BGP-4.
A11:	The following are key attributes of BGP: - Full routing updates are sent at the beginning of the session. - Trigger or incremental updates are sent only after the initial setup. - Connections between BGP routers are maintained by periodic hellos. The Hello protocol is connection-oriented, using TCP, port 179. - It uses the hierarchical structure of autonomous systems. - It has a complex metric, called attributes, by which traffic paths can be manipulated.
12:	What is the default hello update timer for IS-IS on broadcast media?
A12:	The update hello timer for IS-IS on broadcast media is every 10 seconds.
13:	On a broadcast link, how long does OSPF wait by default before it determines that a neighbor is dead?
A13:	On a broadcast link, OSPF would wait 40 seconds before declaring the neighbor as unavailable or dead. This would result in the creation and flooding of an LSA.
14:	What is iBGP?
A14:	The acronym iBGP stands for internal BGP; it is used to traverse an autonomous system. An internal routing protocol is required to carry updates from one part of the autonomous system to another.
15:	When does OSPF send updates?
A15:	Incrementally. The update only contains the network change. However, 30 minutes after the last update is received, a compressed version of the table is propagated.
16:	When does BGP send updates?
A16:	BGP sends incremental updates that contain only the network change.
17:	What is a topological database?
A17:	Used by EIGRP and OSPF, this table records all the routes in the network before determining which will be entered into the routing table.
18:	What is an adjacent neighbor?
A18:	A neighbor is a router that is directly connected to another router. They must also have the same mask and hello parameters. Once a neighbor relationship is formed , routing updates can be exchanged. An adjacent router is a router that has exchanged routing information with its neighbor, becoming an adjacent neighbor.
19:	What is a triggered update?
A19:	A triggered update is when a routing update is sent asynchronously in response to a change in the network topology. If there is a change in the metric, the update is sent immediately without waiting for the update timer to expire.
20:	What is required for iBGP to operate ?
A20:	The iBGP is used to send routing information internally across an autonomous system, using it as a transit area to another autonomous system. The iBGP needs a fully meshed BGP network, but these routers do not need to be directly connected. The way the BGP updates can be sent to the other BGP routers, or the BGP data traffic can find the remote destination, is by listening to the interior IP routing protocol. Although the remote peer does not have to be directly connected, there is an entry in the routing table for the remote peer so that the routers can communicate with each other.