CCNA 2 Chapter 7
What 2 characteristics does a distance vector use to advertise?
* Distance - how far to the destination network - based on metrics like hop count, cost, bandwidth, delay, etc. * Vector - the direction of the next-hop router or exit interface to reach the destination
What 2 types of routing protocols does the internet require?
* IGP (interior gateway protocols) - used for routing within AS - used by RIP, EIGRP, OSPF, and IS-IS * EGP (exterior gateway protocols) - used for routing between AS - used by BGP (official routing protocol used by the internet)
What are the 2 link-state routing protocols IPv4 IGPs.
1. OSPF - popular standards based 2. IS-IS - popular in provider networks
Which commands are used to enable RIPng?
1. R1(config)# ipv6 unicast-routing 2. to enter RIPng configuration mode: ipv6 router rip (ID) 3. int g/0 4. ipv6 rip (ID) enable * ipv6 routing table will show networks with metrics of 2
What are the 4 distance vector routing protocols for IPv4 IGPs?
1. RIPv1 - 1st generation legacy 2. RIPv2 - simple distance 3. IGRP - 1st generation Cisco 4. EIGRP - advanced Cisco vector
Which kind of routes are contained in the Cisco IPv4 routing table?
1. Ultimate- next hop or exit interface 2. Level 1-network, subnet, or default route 3. Level 1 parent- subnetted network route 4. Level 2 child- subnet of classful network address
What are 4 disadvantages of dynamic routing?
1. can be more complex to implement 2. less secure - interfaces send routing updates out 3. routes taken may differ between packets 4. routing algorithm uses additional CPU, RAM, and link bandwidth
What are the 4 main components of dynamic routing protocols?
1. data structures - routing tables 2. messages (incoming & outgoing on interfaces) - to discover neighboring routers, exchange router info, and learn about remote networks with other routers using the same routing protocol 3. when a router detects a topology change the routing protocol advertises this change to other routers 4. algorithm - steps used to complete a task and determining the best path
List 4 overhead disadvantages of Link-State Routing protocols:
1. database & SPF tree uses memory 2. calculating SPF algorithm uses CPU 3. LSP flooding adversely affects bandwidth 4. requires a lot of hardware resources
What are 3 disadvantages of static routing?
1. difficult to implement in a large network 2. managing static configurations can be time consuming 3. if a link fails, a static route can't reroute traffic
What are 4 advantages of static routing?
1. easy to implement in a small network 2. very secure - no advertisements are sent 3. route to destination does not change - easy to troubleshoot 4. no routing algorithm or update messages are needed so very little overhead is needed (CPU or RAM)
What are 3 advantages of dynamic routing?
1. good for topologies with multiple routers - scalable 2. independent of the network size 3. automatically determine better routes if the topology changes
What can't RIPv1 and IGRP do?
1. include subnet masks in their updates 2. VLSMs 3. CIDR interdomain routing
When a packet arrives on a router interface, in what order does the router choose a route to forward the packet?
1. level 1 Ultimate network route 2. level 2 child route of a level 1 parent route 3. level 1 supernet 4. default route 5. if no match is found - packet is dropped
List 4 advantages of Link-State Routing Protocols:
1. router builds topological map of network to determine the shortest path 2. faster convergence achieved by immediate flooding of LSPs 3. LSPs only sent when topology changes 4. hierarchical design
What is the purpose of algorithms for distance vector routing protocols?
1. sending & receiving updates 2. calculate and install the best path 3. detect and react to topology changes
What 3 factors affect the time to convergence?
1. size of the network 2. speed of the links 3. type of protocol used
What are 2 convergence properties?
1. speed of propagation of routing info - amount of time routers take to forward routing info 2. calculation of optimal paths
What is AS?
An autonomous system - collection of routers under a common company or organization
What is the official routing protocol of the internet?
BGP - borderless gateway protocol
What is meant by "best match" in the routing table?
Best match = longest match: the destination IPV4 packet address is compared to routes in the routing table - looking for the maximum # of far left bits to match.
Compare/Contrast RIPv1 and RIPv2:
Both use hop count metric - maximum # of hops is 15. RIPv1 - updates go to 255.255.255.255 RIPv2 - updates go to multicast 224.0.0.9 Only RIPv2 supports VLSM, CIDR, Summarization, and Authentication.
Compare/contrast IGRP & EIGRP:
Both use metric - bandwidth & delay IGRP - updates go to 255.255.255.255 EIGRP - updates go the 224.0.0.10 Only EIGRP supports VLSM, CIDR, Summarization, and Authentication.
What is the biggest difference between classful (RIPv1 & IGRP) & classless (RIPv2, EIGRP, OSPF, and IS-IS) routing protocols?
Classful does not send subnet mask info in their routing tables and classless do.
Compare AD of routing protocols:
Connected = 0 Static = 1 EIGRP = 90 OSPF = 110 RIP = 120
What do link-state protocols do?
They forward updates when the state of a link changes.
What do RIPv2, EIGRP, OSPF, and IS-IS support?
VLSM and CIDR
When is a network considered converged?
When all routers have complete and accurate info about the entire network including best paths and updated routing tables.
What metric is EIGRP based on?
bandwidth, delay, reliability, load, and MTU
What metric is OSPF based on?
cost of overhead
What is a split horizon?
distance vector routing protocols implement a routing loop prevention technique which prevents information from being sent out the same interface in which it was received
Where should link-state protocols be used?
hierarchical networks - usually large networks where fast convergence of the network is crucial
What metric is RIP based on?
hop count
Metrics are used by routing protocols to determine the best path to a destination network. What determines metrics?
hops, bandwidth, cost, delay, reliability, and load
Which protocol is used by BGP?
path vector protocol - maintains path info
What is the primary benefit of using dynamic routing protocols?
routers exchange routing information when the topology changes automatically, such as new networks and alternate paths when there is a link failure.
When a router powers up, it does not even know that there are devices on the other end of its links. What happens next?
1. the router applies configuration stored in NVRAM & discovers its own directly connected networks 2. next, the routing table is updated with all directly connected networks and the interfaces those networks reside on 3. if a routing protocol is configured, the router begins exchanging routing updates to learn about any remote networks 4. the router sends an update packet out all enabled interfaces (contains routing table) and at the same time, the router receives and processes similar updates from other connected routers 5. when the router receives the updates, it checks the updates for new network info to add networks that aren't already listed into the routing table 6. another exchange of routing information gives routers full knowledge about a converged network
What are the 3 reasons to use dynamic routing protocols?
1. to maintain routing tables 2. to discover the network 3. to calculate the best path
Which algorithm is used by the OSPF routing process to construct the SPF tree on a router?
Dijkstra's algorithm
What is the difference between interior gateway protocols (IGP) and exterior gateway protocols (EGP)?
IGPs communicate within a single autonomous system (AS) and EGPs communicate between multiple ASs
Does IPv6 have child routes?
NO - IPV6 only used Ultimate routes
The acronym for the link-state routing protocol that uses the Dijkstra algorithm for the computation of IPv6 routes is ________________ ?
OSPFv3
What link-state protocol uses the Dijkstra algorithm to compute IPv6 routes?
OSPFv3
List the algorithms used by RIP, IGRP, and EIGRP:
RIP - Bellman-Ford IGRP & EIGRP - DUAL
What do the codes S, D, C, O, L, and R stand foir on the routing table?
S - static route D - dynamic route learned from EIGRP O - dynamic route learned from OSPF R - dynamic route learned from RIP C - directly connected network L - local route
