Cisco CCNP Enterprise 300-410 Questions & Answers

• Question 631:

  You have two autonomous systems connected by more than one ASBR.

  Which strategy does Cisco recommend in this situation?

  A. Use two-way redistribution.

  B. Use a default route in both directions.

  C. Allow routes to be exchanged in one direction, and use a default route in the other direction.

  D. Manually configure routes in all ASBRs, and update the configuration each time there is a change in either AS.

  Correct Answer: C

  If there is a single autonomous system border router (ASBR) connecting two autonomous systems (AS), Cisco generally recommends full two-way route redistribution. But when there are multiple ASBRs, as in this scenario, two-way route

  redistribution may result in routing loops. One solution is to use a default route in one direction and allow routes to be exchanged in the other direction.

  Default routes in both directions will almost certainly cause routing loops.

  Manual configuration of static routes would work, but the administrative maintenance necessary when there are changes would be considerable.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify redistribution between any routing protocols or routing sources

  References:

  Cisco > Home > Support > Technology Support > IP Routing > Technology Information > Technology White Paper > OSPF Design Guide > OSPF Design Tips

• Question 632:

  You are configuring a DHCP server to service a group of clients that are located on a different subnet than the DHCP server itself. What else must you configure to ensure a successful setup?

  A. Relay agent

  B. Multicast routing

  C. Unicast routing

  D. Access list

  Correct Answer: A

  If a DHCP server needs to service clients in a different subnet, you will need to configure a relay agent. The relay agent service is enable by default but does not function unless you provide the IP address of the remote DHCP server, which is

  done by executing the ip helper address command on the interface where the address needs to be announced.

  The fact that the clients are on a different subnet indicates that there is a router between the DHCP server and the clients. The DHCP discover packet that a client sends out is in the form of a broadcast. Routers do not forward broadcast

  traffic from one segment to the other. Without a relay agent, the DHCP server would never receive the requests.

  A relay agent resides on the same segment as the clients. When a client sends out a discover packet, the relay agent takes the request, converts it to a unicast packet, and forwards the request to the DHCP server on the other network

  segment.

  The relay agent can also be activated on the router that separates the two network segments. To enable the relay agent service on a Cisco router where 172.16.10.2 is the IP address of the DHCP server, use the following command:

  Router(config-if)# ip helper-address 172.16.10.2

  A relay agent can also be used to assist in the auto configuration of a switch. Auto configuration is a process whereby:

  1.

  A switch boots up.

  2.

  The switch obtains an IP address, subnet mask, and gateway address (optional).

  3.

  The switch uses the DNS server to locate the TFTP server.

  4.

  The switch connects to the TFTP server, downloads the configuration file, and applies it.

  When the switch must broadcast to locate the DHCP, DNS, or TFTP server, IP helper addresses can be provided for all of these. When the switch broadcasts, a unicast will be sent to all of these addresses.

  In following illustration, the FastEthernet0 interface of the router is connected to the subnet containing the switch and the FastEthernet1 interface of the router is connected to the subnet containing the DHCP, DNS, and TFTP servers. The addresses involved are: Switch - 10.2.2.2 Router - F0 10.2.21, F2 20.2.2.2 DHCP - 20.2.2.5 DNS - 20.2.2.6 TFTP - 20.2.2.7

  The router that is located between the subnet containing the switch and the subnet containing the DHCP, DNS, and TFTP servers should be configured as shown below:

  

  Regardless of whether the ip helper-address command has been used to aid in the DHCP configuration of a switch utilizing auto configuration, or to aid DHCP clients in a different subnet from the DHCP server, the DHCP relay service will

  provide relay services for the following UDP protocols by default:

  Trivial File Transfer Protocol (TFTP) (port 69)

  Domain Naming System (DNS) (port 53)

  Time service (port 37)

  NetBIOS Name Server (port 137)

  NetBIOS Datagram Server (port 138)

  Boot Protocol (BOOTP) client and server packets (ports 67 and 68) TACACS service (port 49)

  IEN-116 Name Service (port 42)

  This default behavior can be altered with the IP forward-protocol udp command executed in global configuration mode.

  Multicast routing, unicast routing and access lists do not aid in the DHCP communication process.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Identify, configure, and verify IPv4 addressing and subnetting

  References:

  Cisco > IP Addressing: DHCP Configuration Guide > Configuring the Cisco IOS DHCP Relay Agent

• Question 633:

  Which of the following commands will enable the DHCP and relay services on a Cisco router?

  A. RouterA(config)# service dhcp

  B. RouterA(config)# dhcp enable

  C. RouterA(config)# enable dhcp

  D. RouterA(config-if)# dhcp enable

  E. RouterA(config-if)# service dhcp

  Correct Answer: A

  Using the service dhcp command at global configuration mode will enable the DHCP and relay services on a Cisco router. By default, these services are already enabled on the router, but they can be disabled using the no service dhcp command. Before the DHCP service can actually function, a pool of addresses must be created and any statically defined addresses (such as the router itself) must be excluded. If the router has two interfaces and needs to issue addresses on both interfaces two pools and two exclusion statements must be present.

  Below is an example of a complete configuration taken from a partial output of the show run command. This router has two interfaces 10.0.0.1/24 and 192.168.5.1/24, creating the need for two pools and two exclusion statements. It excludes the address ranges 10.0.0.1-10.0.0.5 from the 10.0.0.0/24 pool and excludes 192.168.5.1-192.168.5.5 from the 192.168.5.0/24 pool, and creates a pool for 10.0.0./24 and 192.168.5.0/24.

  

  The commands RouterA(config)# dhcp enable and RouterA(config)# enable dhcp are incorrect because the syntax is incorrect.

  The command RouterA(config-if)# dhcp enable is incorrect because the syntax is incorrect and because it is executed in interface configuration mode. Enabling DHCP is done at the global prompt.

  The command RouterA(config-if)# service dhcp is incorrect because it is executed in interface configuration mode. Enabling DHCP is done at the global prompt Objective:

  Layer 3 Technologies

  Sub-Objective:

  Identify, configure, and verify IPv4 addressing and subnetting

  References:

  Cisco > IP Addressing: DHCP Configuration Guide, Release 15MandT > DHCP Overview Cisco > Cisco IOS IP Addressing Services Command Reference > service dhcp

• Question 634:

  You have enabled RIPng on one of the interfaces of a router with the basic configuration. You have assigned an address to that interface using the ipv6 address command.

  Which of the following statements should appear in the output of the show running-config command executed on the router? (Choose all that apply.)

  A. ipv6 unicast-routing

  B. ipv6 enable

  C. ipv6 rip enable

  D. ipv6 router rip

  E. ipv6 unnumbered

  F. ipv6 prefix-list

  Correct Answer: AC

  The ipv6 unicast-routing and ipv6 rip enable statements should appear in the output of the show running-config command.

  The ipv6 unicast-routing command is one of the basic IPv6 commands that needs to be executed on any router for IPv6 processing. This command is executed in the global configuration mode to allow IPv6 packet forwarding on the router.

  When it has been executed the ipv6 unicast-routing statement will appear in the output of the show run command.

  The ipv6 rip enable command allows you to enable RIPng on a router interface. You should execute this command to create a RIPng routing process. When it has been executed the ipv6 rip enable statement will appear in the output of the

  show run command.

  The ipv6 router rip command allows you to work with RIPng routing process by entering the router configuration mode for RIPng. It will only appear if modifications have been made to the RIPng routing process, which is not mentioned in this

  case.

  The commands to configure a router with RIPng is as follows:

  rtrA(config)# ipv6 unicast-routing

  rtrA(config)# interface Fa0/1

  rtrA(config-if)# ipv6 rip rip process enable

  rtrA(config-if)# ipv6 address 2001:1:1:1::1/64

  Important note: in the command set above, the command that enables the RIP process on interface Fa0/1 is executed before the command assigning the IPv6 address. The order of execution of those two commands does not matter.

  However, if a configuration file is copied and pasted into a router, then the order in which the statements appear does matter.

  For example, if the partial configuration below were pasted into a router, the IPv6 RIP process 56 would not be enabled on Fa0/0:

  ip unicast routing

  interface Fa0/0

  ipv6 rip 56 enable

  ipv6 address 2001:1:1:1::1/64

  The system would reject the ipv6 rip 56 enable command because an IPv6 address is not yet present. If the commands were reversed in the file, the system would accept the ipv6 rip 56 enable command.

  In the scenario, the ipv6 enable command does not appear in the show running-config output. This command enables IPv6 routing on a router interface that has not been assigned an IPv6 address. In this case, an IPv6 address is explicitly

  assigned to the router interface by using the ipv6 address command. Therefore, the ipv6 enable command is not required.

  The ipv6 unnumbered interface type command does not appear in the show running-config output. This command will allow you to enable IPv6 without assigning an IPv6 address to a router interface.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Describe RIPng

  References:

  Cisco IPv6 Implementation Guide, Release 15.2MandT > Implementing RIP for IPv6 > How to Implement RIP for IPv6 > Enabling the IPv6 RIP Process Cisco IPv6 Implementation Guide, Release 15.2MandT > Implementing RIP for IPv6 >

  Configuration Examples for IPv6 RIP > Examples: IPv6 RIP Configuration Cisco IOS IPv6 Command Reference > ipv6 ospf dead-interval through ipv6 split-horizon eigrp > ipv6 rip enable Cisco IOS IPv6 Command Reference > ipv6 ospf

  dead-interval through ipv6 split-horizon eigrp > ipv6 router rip Cisco > Cisco IOS IPv6 Command Reference > ipv6 prefix-list Cisco IOS IPv6 Command Reference > ipv6 summary-address through mpls ldp router-id > ipv6 unnumbered

• Question 635:

  Company A recently acquired Company B and the network infrastructures are being merged. Both organizations used non-overlapping globally unique network addressing but different Interior Gateway Protocols (IGPs). Initially, multiple WAN links will connect the two organizations. Company A will maintain its core routing protocol, and Company B's routing protocol will be the edge routing protocol. Two-way redistribution will be used to ensure full network routing capability.

  What additional routing configuration should be performed to prevent routing loops and suboptimal routing?

  A. Manually configure static routes.

  B. Manually configure default routes.

  C. Manually adjust the administrative distances.

  D. Manually adjust the local preference attribute.

  Correct Answer: C

  When routes are being redistributed from the core into the edge and from the edge into the core, the administrative distance (AD) associated with external routes should be modified. This lessens the possibility of sub-optimal routing when

  multiple routing protocols advertise different paths to the same network. The AD associated with the externally advertised routes should be higher than the internal IGP's AD. To change the AD for an entire routing protocol, use the distance

  command. An example and the command syntax are shown below:

  router(config)#router rip

  router(config-router)#distance 125

  The complete syntax of the distance command is:

  distance weight [address mask [ access-list-number | name]

  The weight parameter is the AD, which can be a number from 10 to 255. Note that distances 0 through 9 are reserved for system use.

  To change only the AD for selected networks, use an access list with the distance command as shown below:

  router(config)# access-list 5 permit 10.0.0.0 255.0.0.0

  router(config)# access-list 5 permit 11.0.0.0 255.0.0.0

  router(config)# access-list 5 permit 12.0.0.0 255.0.0.0

  router(config)# router rip

  router(config-router)# distance 220 0.0.0.0 255.255.255.255 5

  The 0.0.0.0 255.255.255.255 portion included with the distance command could hold an address/mask combination for a single address, but it is more common to use an access list.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify redistribution between any routing protocols or routing sources

  References:

  Cisco > Cisco IOS IP Routing: Protocol-Independent Command Reference > distance (ip) Cisco > Support > Technology Support > IP > IP Routing > Design > Design Technotes > What Is Administrative Distance? > Document ID: 26634

• Question 636:

  Which show command displays entries in a router's Border Gateway Protocol (BGP) table?

  A. show ip bgp

  B. show ip bgp table

  C. show ip bgp topology

  D. show ip bgp summary

  Correct Answer: A

  The correct command is show ip bgp.

  The BGP table lists all the paths that the BGP router has learned. Each destination network listed might have multiple possible paths listed. Given that the criteria are met for each destination network, BGP will choose a path to put in the IP routing table.

  The BGP table is in many ways analogous to EIGRP's topology table in that it lists many known paths, not just the best path. Below is an example partial output of the show ip bgp command:

  

  The following facts can be determined from this output:

  All of the routes were redistributed into BGP from an IGP. In the status column (located to the left of the Network column and to right of the column where some lines have a > symbol) is a column that is either blank or has an i symbol. In this

  case, all of the columns are blank. If the status column is blank, then BGP learned the route from an external peer. If it has an i symbol, an iBGP neighbor advertised this path to the router. It was learned from an Interior Gateway Protocol

  (IGP) and was advertised as a result of executing a network statement on the neighbor under the router bgp context as shown below adding the 30.0.0.0 network under BGP 100.

  R4(config)#router bgp 100

  R4(config-router)#network 30.0.0.0

  Four routes will be installed in the routing table. These routes have both an * symbol and a > symbol. l in the status column. The * symbol indicates that the next hop is valid and the > symbol indicates that this is the best route.

  The output is slightly different if you specify the network that you are interested in, as shown below in the show ip bgp 214.5.98.0 command output:

  

  This output focuses solely on the route to the network 214.5.98.0 and provides the following pieces of information:

  The neighbor that sent this route is at 192.168.1.1

  The AS of the network where 214.5.98.0 is located is 5760

  The IGP metric to reach the neighbor that sent this route is 886, as shown by the text 192.168.1.1 (metric 886) The complete metric to 214.5.98.0 is 1652, as shown in the last line by Origin IGP, metric 1652

  The commands show ip bgp table and show ip bgp topology are not valid Cisco commands.

  The show ip bgp summary command displays the status of BGP connections.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Explain BGP attributes and best-path selection

  References:

  Cisco IOS Master Command List, Release 12.4 > l through q > Cisco IOS IP Routing: BGP Command Reference > show ip bgp

• Question 637:

  Your company has a policy of creating all configurations in text files, checking the files, and then applying the configurations to the devices. Your assistant has presented you with the following partial configuration that she plans to execute on a router:

  interface S0/0/1 ipv6 address 2001:610:FFFF:1::1/64 ipv6 ospf 100 area 0

  ipv6 router ospf 100 router-id 10.1.1.6

  The configuration is supposed to accomplish the following: Enable IPv6 routing Assign a router ID Assign an IPv6 address to the interface Place the interface in OSPF area 0

  Which step does this configuration NOT complete?

  A. Enable IPv6 routing

  B. Assign a router ID

  C. Assign an IPv6 address to the interface

  D. Place the interface in OSPF area 0

  Correct Answer: A

  The configuration indicates all steps are complete except for globally enabling IPv6 routing. If that had been done, the configuration output would have reflected it under the interface as follows:

  interface S0/0/1

  ipv6 address 2001:610:FFFF:1::1/64

  ipv6 ospf 100 area 0

  ipv6 enable

  ipv6 router ospf 100

  router-id 10.1.1.6

  Prior to configuring OSPFv3 on an interface, it must be enabled globally. OSPFv3 is an OSPF version specific to IPv6. The following commands will globally enable OSPF v3. It will then be reflected by the ipv6 enable statement under the

  interface when viewing the configuration as shown in the fourth line of the output above.

  Router5(config)# ipv6 unicast-routing

  Router5(config)# ipv6 ospf 100

  Router5(config-rtr)# router-id 10.1.1.6

  The problem is not the router ID. The configuration in the scenario does assign a router ID, as indicated by these lines:

  ipv6 router ospf 100

  router-id 10.1.1.6

  The problem is not the IPv6 address. The configuration does assign an IPv6 address to the interface, as indicated by these lines:

  interface S0/0/1

  ipv6 address2001:610:FFFF:1::1/64

  OSPF area 0 is not the problem. The configuration does place the interface in OSPF area 0, as indicated by these lines:

  interface S0/0/1

  ipv6 ospf 100 area 0

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify OSPF for IPv6

  References:

  Cisco > Implementing OSPF for IPv6 > How to Implement OSPF for IPv6

• Question 638:

  Which EIGRP packet type is sent as a multicast when a new route is discovered, and sent as a unicast to synchronize topology tables when neighbors initialize?

  A. ACK

  B. Hello

  C. Update

  D. Replies

  E. Queries

  Correct Answer: C

  EIGRP update packets are sent as a multicast when a new route is discovered, and sent as a unicast to synchronize topology tables when a neighboring router initializes.

  Whenever EIGRP only needs to communicate with a single neighbor, it sends a unicast to that neighbor instead of the standard multicast. In this case, it unicasts a packet to update a new EIGRP router on the network with the information that

  all other routers on that network already know.

  Hellos for neighbor discovery and maintenance are always multicasts.

  ACKs are hellos without data, and are always unicast.

  Queries are always multicast.

  Replies to queries are always unicast.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Describe EIGRP packet types

  References:

  Internetworking Technology Handbook > Enhanced Interior Gateway Routing Protocol (EIGRP) > EIGRP Packet Types

• Question 639:

  Which command can you use to display information about OSPF virtual links?

  A. debug ip ospf adj

  B. show ip ospf [process-id]

  C. show ip ospf virtual-links

  D. show ip ospf border-routers

  Correct Answer: C

  The correct answer is show ip ospf virtual-links. The show ip ospf virtual-links command displays the current state of OSPF virtual links, as shown below.

  

  The following additional commands are available to verify OSPF configurations: show ip ospf border-routers, debug ip ospf adj, and show ip ospf.

  The show ip ospf border-routers command displays internal OSPF routing table entries for an ABR, as shown below.

  router10#show ip ospf border-routers

  Codes: i - Intra-area route, I-Inter-area route

  Type Dest Address Cost NextHop Interface ABR ASBR Area SPF

  i 2.2.2.2 10 192.1.1.199 Ethernet 2 TRUE FALSE 0 3 i 3.2.2.2 10 192.1.1.200 Ethernet 2 TRUE FALSE 0 3 The show ip ospf command displays information about the router's role and each area to which the router is connected, as shown below.

  

  The debug ip ospf adj command displays information about the state of neighbor adjacencies, as shown below.

  R3#debug ip ospf adj OSPF adjacency events debugging is on

  00:54:04: OSPF: Rcv pkt from 172.12.23.2, Ethernet0, area 0.0.0.1 : src not on the same network

  In the above example, either the IP address or the subnet mask is misconfigured on either this router or the neighbor.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify network types, area types, and router types

  References:

  Cisco > Cisco IOS IP Routing Protocols Command Reference > IP Routing Protocol-Independent Commands:

  S through T > show ip ospf virtual-links

• Question 640:

  For a non-ISP autonomous system (AS), which combination of two conditions will require redistribution from BGP into Interior Gateway Protocol (IGP)? (Choose two.)

  A. All routers run BGP.

  B. Not all routers run BGP.

  C. No knowledge of external routes is required inside the AS.

  D. Routers inside the AS require knowledge of external routes.

  Correct Answer: BD

  For non-ISP autonomous systems (AS), redistribution into IGP is required when BOTH of the following conditions exist:

  Not all routers run BGP

  Knowledge of external routes is required inside the AS

  Note: Redistribution of any BGP routes into your IGP can cause serious problems, even if your internal routers can handle the load. This should be done rarely, if at all. If you do decide to do this, configure heavy filtering to allow only very few

  routes into OSPF or EIGRP so as not to overwhelm those protocols. For instance, do it only for a select group of networks for which optimal routing is critical.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify redistribution between any routing protocols or routing sources

  References:

  Cisco > Support > Technology Support > IP > IP Routing > Design > Design Technotes > BGP Case Studies > Document ID: 26634 > Static Routes and Redistribution Cisco > Cisco IOS IP Routing: BGP Configuration Guide, Release 12.4 >

  Cisco BGP Overview > Information About Cisco BGP > BGP Autonomous Systems