Details Title: CCNA 5 Description: IP Routing Total Flash Cards: 52 Created: 11/02/2008 12:31:09		New Users: To study from this flashcard set, or to create your own your own study flash cards, REGISTER HERE. Existing Users: CLICK HERE. Additional Engineering Flashcards
Cards in this set: Term What are the three kinds of routes that control routing decisions on a router? Definition static routes   default routes   dynamic routes Term What is the command syntax for static routes? Definition ip route <dest ip> <mask> <next hop/intfc> <dist> Term What are the syntax to configure a default route? Definition ip route 0.0.0.0 0.0.0.0 <intfc/next-hop>   ip default-gateway <next-hop>   or   ip default-network <netwk> (specified network must be found in routing table) Term What are the administrative distances for the following routing protocols and which is preferred?   Connected EIGRP (internal/external) IGRP IS-IS OSPF RIP Static (not configured) Definition Lowest AD is preferred   Connected - 0 Static (default) - 1 EIGRP (internal) - 90 IGRP = 100 OSPF - 110 IS-IS = 115   RIP - 120  EIGRP (external) - 170 Term What is used to determine the metrics for the following protocols:   RIP EIGRP OSPF Definition Rip - hop count   EIGRP - bandwidth and delay (can also factor reliability, load, MTU)   OSPF - cost = 10^8 / bandwidth Term What are the characteristics of distance vector routing protocols? Definition periodically broadcasts routing table   trust info from other routers (route by rumor)   Term What are the mechanisms to prevent looping in distance vector protocols? Definition maximum hop count   split-horizon   route poisoning   poison reverse   hold down timers   triggered updates Term What are the maximum hop counts for:   RIP   EIGRP Definition RIP - 15   EIGRP - 224 Term What does split horizon refer to? Definition Info about a route should not be sent back the direction (interface) it was learned from Term How do route poisoning and poison reverse work in the event that a network becomes unreachable? Definition route poisoning will advertise down network with hop count larger than maximum   poison reverse will violate split horizon and send a report of the network being unreachable Term What is the role of hold down timers in preventing loops and what is the default timer value for RIP? Definition When a network is reported down, router will not accept any new info from the reporting router for a specified amount of time, to prevent regular update messages from reinstating a down route   RIP hold down timer = 180 seconds Term What are the unique characteristics of EIGRP? Definition Hybrid protocol (between distance vector and link state)   Cisco proprietary Term What routing protocol supports multiple L3 protocols as opposed to only IP?   (And what are the three major protocols supported?) Definition EIGRP   (IP, AppleTalk, IPX) Term What are the three tables maintained by EIGRP? Definition Neighbor table   Topology table   Routing table Term What are EIGRP Hello packets for? Definition Used to exchange routes between neighbors. Term What algorithm is used by EIGRP to build a map of the network?   And what information does it use?   What kind of routes does it determine? Definition DUAL (Diffusing Update Algorithm)   uses info from topology table   determines successor route and feasible successor route Term What are the two kinds of routes determined by EIGRP and what are their characteristics? Definition Successor Route - best route determined by DUAL; injected into the routing table as the one used to route traffic   Feasible Successor Route - next best route to successor route; kept in topology table for backup Term What administrative distance values does EIGRP have?   (And how is it distinct from other routing protocols?) Definition EIGRP uses two administrative distances   90 - routes learned via EIGRP   170 - routes redistributed from another routing protocol Term What are the elements/commands required to configure EIGRP? Definition 1. AS (autonomous system) number - global; must be same on all routers   Router(config)#router eigrp [asn]   2. Add networks (with optional wildcard mask)   3. Optional - Enable classless routing   Router(config-router)#no auto-summary Term What commands can be used to verify (show) and debug EIGRP config/operations? Definition show ip route eigrp   show ip eigrp topology   show ip eigrp neighbors   debug ip eigrp Term What does LSA stand for and what are they for? Definition Link State Advertisements   Used by OSPF to send updates when there is a change in the network. Term What is the process for OSPF to discover neighbor devices? Definition OSPF sends out hello messages to neighbors announcing itself as an OSPF router   Verify matching parameters (eg. timers, subnet) before they are recognized as neighbors   Routers send LSAs containing info about known networks/routes Term What algorithm does OSPF use to determine routes? Definition SPF (Shortest Path First)   aka Dijkstra algorithm Term How does OSPF determine the cost of a link? Definition cost = 10^8 / bandwidth   eg. for bandwidth = 100 Mbps, cost = 1 Term For link state cost analysis, which link is preferred? (And for OSPF, what are their costs?) 1. a 10 Mbps ethernet connection   2. a T1 (1.544Mbps)   3. a 64 Kbps connection Definition   10Mbps ethernet connection preferred   1. 10 Mbps -> 10   2. 1.544Mbps -> 64   3. 64 Kbps -> 1562 Term What is the command to change the reference bandwidth for OSPF to 1 GB (10^9) Definition auto-cost reference-bandwidth 1000000 Term What is the area id for the "backbone" area for OSPF and how does it relate to other areas? Definition Area 0   All other areas must be connected to it. Term What is the purpose of a designated router in an OSPF network? Definition Conserve bandwidth by having all other routers (more than one) communicate with the DR instead of each other in full mesh Term In OSPF, what is the process for electing a desginated router and backup DR? Definition 1. router with highest priority on the segment becomes DR (and second highest becomes BDR)    if tie:   2. router with the highest router ID becomes DR Term In OSPF, how is the router priority determined? Definition Configured using the command:   ip ospf priority [0-255]   Default value is 1   If priority = 0, router cannot become DR/BDR  Term In OSPF, how is the router ID in determined? Definition 1. Configured with the command   router-id [ip]   2. Highest IP address of any loopback   3. Highest IP address of any physical interface Term What are the required commands to configure OSPF? Definition 1. Enable protocol with a local process id   router ospf [1-65535]   2. Add networks using wildcard (not subnet) mask   network [ip] [mask] area [id]   eg. network 11.11.11.0 0.0.0.255 area 0 Term What are the optional commands that can be configured for OSPF under the interface? Definition ip ospf priority [priority]     ip ospf cost [cost] Term What are the commands to verify (show) and troubleshoot (debug) OSPF? Definition show ip route ospf - routing table filtered on ospf   show ip ospf interface - area, DR, BDR info   show ip ospf neighbor - neighbor info   debug ip ospf events - troubleshoot neighbor relationship setup Term What algorithm does RIP use to select paths and how does it work? Definition Bellman-Ford algorithm   Counts the number of hops to destination and chooses path with fewest hops   Any path with more than 15 hops is deemed inaccessible Term What kind of info does RIP send out, and how is it sent? Definition Entire routing table broadcasted every 30 seconds Term What are the advantages of RIP v2 over RIP v1? Definition Routes multicasted instead of broadcast   MD5 authentication   Classes routing/VLSM (Variable Length Subnet Masks)   Summarization Term What is the process/commands for enabling RIP? Definition 1. router rip   2. Activate the interfaces/advertise direct networks   network x.x.x.x   3. Optional parameters:   version 2 no auto-summary Term What are the commands to verify (show) and troubleshoot (debug) RIP? Definition show ip route   show ip protocols   debug ip rip Term If a packet is routed across both switches and routers, what is the destination MAC address when leaving the sending host? Definition MAC address of the next router (not switch) Term What OSPF command injects the default route into an area? Definition Router(config-router)#default-information originate Term What happens when there are no routing updates from a RIP neighbor past the timeout interval? Definition All paths from that neighbor will be dropped from routing table.   timeout interval of 4 mins. Term Which routing protocols support unequal cost path load balancing? Definition IGRP EIGRP Term Which routing protocols are classful? Definition RIP v1   IGRP Term Under what conditions will OSPF elect a (backup) designated router? Definition Segment with broadcast and nonbroadcast multi-access   (ie. where there are conditions of more than one routers connected to a router) Term Over what links can OSPF establish adjacency without DR/BDR elected? Definition point-to-point Term What are OSPF Hello packets used for? Definition  Dynamic neighbor discovery   Keepalives Term What IP is OSPF Hello packets addressed to? Definition Multicast IP 224.0.0.5 Term For EIGRP, what happens when both the successor and feasible successor routes are down? Definition Multicast hello packets to neighbors again to find new successor route. Term What is route summarization and what are its major advantages? Definition aggregate smaller contiguous networks into larger network address with a shorter subnet mask    pros:   keeps routing table small & manageable  reduces load and network overhead hides instability in the system behind the summary improves scalability of routing Term What criteria is used to determine which route is placed in the routing table given multiple routes to the same destination? Definition   1. If learned from different routing protocols: use route with lowest administrative distance   2. If learned from same routing protocol: use route with lowest metric/cost   3. If all else above the same, use route with the longest prefix match Term What does VLSM stand for and what does it do? Definition Variable Length Subnet Masking   capabilitiy to apply more than one subnet mask to a given class of addresses throughout a routed system   eg. route advertised with a /26 and a /30 mask