Chapter 5 - Infrastructure Services Flashcards
1
Q
- Which method provides a distributed database that is used to resolve FQDNs to an IP address?
A. Hostnames B. Hosts files C. DNS
D. ARP
A
- C. Domain Name Services (DNS) is a distributed database of fully qualified domain names (FQDNs) to IP addresses.
2
Q
- What statement is correct about forward lookups?
A. Forward lookups resolve IP addresses from the queried DNS server, without the help of other DNS servers.
B. Forward lookups resolve FQDNs to IP addresses.
C. Forward lookups resolve IP addresses to FQDNs.
D. A forward lookup forwards a request to another DNS server.
A
- B. Forward lookups resolve fully qualified domain names (FQDNs) to an IP address.
3
Q
- Which protocol and port number does DNS use for direct queries? A. UDP/53
B. TCP/53 C. UDP/55 D. UDP/68
A
- A. Domain Name Services direct queries are performed over the UDP protocol to port 53. The queries do not require the TCP setup and teardown because the queries are simple request and reply messages, so UDP is used for direct queries
4
Q
- Which statement describes FQDNs?
A. A DNS server always processes the entire FQDN.
B. FQDNs are always registered with a registrar.
C. FQDNs are significant from left to right, starting with a period for the root.
D. FQDNs are significant from right to left, starting with a period for the root.
A
- D. Fully qualified domain names are significant from right to left, starting with a period to signify the root. The period is normally not visible on the FQDN, but it is processed as the root lookup.
5
Q
- Which statement is correct about reverse lookups?
A. A reverse lookup is when the request needs to be reversed to another DNS server.
B. A reverse lookup is the resolution of an IP address to FQDN.
C. A reverse lookup is when the DNS queried can answer the request without asking another DNS server.
D. A reverse lookup is the resolution of an FQDN to an IP address.
A
- B. A reverse lookup is when the fully qualified domain name (FQDN) is resolved from an IP address. This is useful when you want to identify an IP address. From the IP address, you can derive the FQDN.
6
Q
- Which record type is used for an IPv4 address to FQDN for DNS queries?
A. The A record
B. The CName record C. The PTR record
D. The AAAA record
A
- C. The PTR, or pointer record, is used to look up IP addresses and return FQDNs that are mapped to them. This is helpful to identify an IP address, and in the case of SSH, it is used to positively identify the host you are connecting to.
7
Q
- What gets appended to hostname queries for DNS resolution?
A. The DNS domain name B. The DNS zone
C. The host header
D. The hostname PTR record
A
- A. The configured DNS domain name is appended to the hostname query. As an example, if you query a hostname of routera and the configured domain name is network.local, the DNS server will see a query for rotuera.network.local.
8
Q
- Which is the most secure method of name resolution for routers and switches? A. DNS
B. PTR records
C. Static hostname entries
D. LLMNR
A
- C. Static hostname entries are the most secure name resolution method for routers and switches. This is because the switch or router does not need to forward-query a server. However, static hostname entries are not scalable.
9
Q
- Which type of DNS record holds the IPv4 IP address for a hostname?
A. The A record
B. The CName record C. The PTR record
D. The AAAA record
A
- A. The A record is the DNS record that is queried when you want to resolve a hostname to an IP address.
10
Q
- What limits the amount of time that a DNS entry is available in DNS cache?
A. Arecord B. TTL
C. SOA
D. Default of 5 minutes
A
- B. The time to live, or TTL, limits the amount of time in which a DNS entry will be available in the DNS cache. The TTL can be defined by the DNS administrator on the entry, or it can be defined in the SOA record as the default TTL.
11
Q
11. Which is an alternative to DNS lookup on routers? A. Static ARP B. LLMNR C. Hosts table file D. Static hostname entries
A
- D. The alternative to DNS lookup on routers is configuring static hostname entries. This method unfortunately is not scalable.
12
Q
- Which record type is used for IPv6 hostname lookup for DNS queries?
A. The A record
B. The CName record C. The PTR record
D. The AAAA record
A
- D. The Quad-A (AAAA) record type is used for IPv6 hostname lookup on DNS servers.
13
Q
- Which protocol and port number is used for DNS domain zone transfers?
A. UDP/53 B. TCP/53 C. UDP/55
D. UDP/68
A
- B. The protocol TCP and port number 53 are used for DNS domain zone transfers. UDP port 53 is used for iterative queries, since the message is short. However, zone transfers require the help of TCP because there is more information than there is in a query.
14
Q
- What is a reason to configure DNS on a router or switch?
A. ACLs can dynamically reverse hostnames to IPs.
B. Configuration allows access to the router or switch by the FQDN.
C. Configuration allows ease of administration from the router or switch when connecting to other devices by FQDN.
D. Configuration allows secure communications via HTTPS.
A
- C. Configuring DNS on a router or switch allows for ease of administration from the router or switch. It enables DNS resolution from the console. It does not enable DNS resolution from external sources unless you have configured the hostnames on the DNS server.
15
Q
15. You are were trying to type the ping command into the router and mistype it and receive the output of Translating "png". . . domain server (255.255.255.255), which halts you from continuing. Which command will stop this behavior? A. RouterA#no domain-lookup B. RouterA#no ip dns C. RouterA(config)#no ip dns-lookup D. RouterA(config)#no ip domain-lookup
A
- D. By default, all routers and switches are set for ip domain-lookup. Because no IP address is set, the router or switch will try to broadcast the DNS query. If you configure no ip domain-lookup, the query will just fail, and you will not need to break out of it.
16
Q
- Which command will set the resolution of a host so that DNS does not need to be
used for resolution?
A. RouterA(config)#hostname routerb 10.1.2.3
B. RouterA(config)#hostname 10.1.2.3 routerb
C. RouterA(config)#ip hostname routerb 10.1.2.3
D. RouterA(config)#ip host routerb 10.1.2.3
A
- D. The command ip host routerb 10.1.2.3 will configure the local resolution of the host routerb to an IP address of 10.1.2.3.
17
Q
- Which command will configure the router or switch to use a specific DNS server
for hostname lookups?
A. RouterA(config)#ip domain server 172.16.1.5
B. RouterA(config)#ip dns-server 172.16.1.5 C. RouterA(config)#ip name-server 172.16.1.5
D. RouterA(config)#ip domain-server 172.16.1.5
A
- C. The command ip name-server 172.16.1.5 will configure the router or switch to query the DNS server of 172.16.1.5 for hostname lookups. You can specify multiple DNS servers by using a space as a delimiter between each name for fault tolerance
18
Q
- Which command will configure the domain name to append to a DNS query?
A. RouterA(config)#ip domain sybex.com
B. RouterA(config)#dns-domain sybex.com
C. RouterA(config)#ip dns-domain sybex.com
D. RouterA(config)#ip domain-name sybex.com
A
- D. The command ip domain-name sybex.com will set the appended domain name of sybex.com for DNS queries. This command will allow the proper FQDN to be resolved by DNS.
19
Q
- What is at the end of all FQDN addresses?
A. A period, which signifies root
B. Top-level domain names
C. Generic top-level domain names
D. The domain name
A
- A. A period is always appended to all FQDNs. This is significant because it represents the root, where all DNS resolution begins. The root or period is not often visible, but it is part of the DNS recursion process.
20
Q
- When configuring the name server(s) for domain lookup, what is a best practice? A. Always use public DNS servers.
B. Always use TLD servers.
C. Always use private DNS servers.
D. Always use a mixture of public and private DNS servers for fault tolerance.
A
- C. A best practice for security is to always use a trusted DNS server. This is normally a server under the control of the enterprise, so it is a private DNS server.
21
Q
- Which command will help verify the hostnames that are statically configured?
A. RouterA#show hostname B. RouterA#show hosts
C. RouterA#show ip hosts
D. RouterA#show ip host-names
A
- B. The command show hosts will allow you to verify the statically configured hosts.
22
Q
- Your DNS administrator has changed the DNS entry for RouterB. You clear the DNS cache and ping routerb.sybex.com again but still ping the original address. All other DNS addresses work fine. What is the problem?
A. The router is configured to the wrong DNS server. B. RouterB has a host entry configured.
C. The DNS administrator made an error.
D. The domain name of the router is incorrect.
A
- B. If the cache is cleared after the change has been made to DNS and you still get the same IP address, the reason is most likely that there is a host entry configured. The command show running-configuration will show you if there is an entry.
23
Q
- You have configured a router to point to the DNS server with the IP address 10.2.2.2 and configured the domain name of sybex.com. However, you cannot resolve the host routerb .sybex.com. Which Windows command will help you verify DNS name resolution?
A. C:>ping routerb.sybex.com
B. C:>tracert routerb.sybex.com C. C:>nslookup routerb.sybex.com
D. C:>dig routerb.sybex.com
A
- C. The command nslookup routerb.sybex.com will allow you to positively verify name resolution. Ping should not be used because the failure of ICMP echo will make the command fail, giving you a false result.
24
Q
24. Which command will allow you to verify the DNS server you are using for name resolution? A. RouterA#show hosts B. RouterA#show running-configuration C. RouterA#show ip domain D. RouterA#show dns
A
- B. The command to verify DNS server(s) configured for name lookup is show running-configuration. The line to look for in the output is ip name-server x.x.x.x.
25
Q
- You have configured the domain name of sybex.com and the DNS server 10.2.3.4 on a router. However, after you type ping routerb, the console promptly returns “% Unrecognized host or address or protocol not running.” What is wrong?
A. The DNS server is wrong.
B. The domain server is wrong. C. The hostname is wrong.
D. All of the above
A
- D. Options A, B, and C will return the error ““% Unrecognized host or address or protocol not running
26
Q
- Your DNS administrator has changed the DNS entry for RouterB. You ping routerb.sybex .com again, but still ping the original address. All other DNS addresses work fine. What is the problem?
A. The DNS administrator made an error.
B. The router is configured to the wrong DNS server. C. The router’s DNS cache needs to be cleared.
D. The domain name of the router is incorrect.
A
- C. DNS changes can be made on-the-fly. However, the results will not be seen immediately unless all cache is cleared and routers request the new address. The problem would be that this router had resolved routerb.sybex.com already and the entry still exists in the cache, which needs to be cleared.
27
Q
- Which command will remove the entry routerb.sybex.com out of the DNS cache or a switch without affecting the rest of the cache?
A. Router#clear host
B. Router#clear host *
C. Router(config)#clear host routerb.sybex.com
D. Router#clear host routerb.sybex.com
A
- D. The command to clear only the host routerb.sybex.com from the DNS cache is clear host routerb.sybex.com. This will remove only that particular host from the cache.
28
Q
- Which statement is true about the Discover packet of DHCP? A. The layer 3 destination is a unicast to the DHCP server.
B. The layer 2 destination is the MAC address of the DHCP server. C. The layer 2 source is the MAC address of the client.
D. The layer 3 source is a link-local address of the client.
A
- C. The DHCP Discover packet is a broadcast to discover a DHCP server. The layer 3 packet and layer 2 frame are broadcasts. Since the client does not have an IP address yet, the layer 3 source address is all zeros. However, the layer 2 source MAC address is filled out in the frame.
29
Q
- Which command will configure a router to use DHCP for IP address assignment?
A. RouterA(config)#ip address dhcp
B. RouterA(config-if)#ip address auto C. RouterA(config-if)#ip address dhcp
D. RouterA(config)#ip address auto
A
- C. The command ip address dhcp will configure the router to use DHCP for IP address assignment. This command needs to be issued on the interface in which you want the IP address to be configured, similar to static IP address assignment
30
Q
- Which command will allow you to verify the IP address assigned to a router’s
interface?
A. Router#show ip dhcp bindings
B. Router#show ip interface C. Router#show ip lease
D. Router#show ip dhcp lease
A
- B. The command show ip interface will display the IP addresses configured on the router’s interfaces. It will detail which are static and which have been allocated through DHCP.
31
Q
- Which port and protocol does the client use for DHCP messages?
A. UDP/68 B. TCP/68 C. UDP/67
D. TCP/67
A
- A. The DHCP client uses the source port UDP/68 to await connections back from the server. It keeps this protocol and port open in an active state until DHCP is complete.
32
Q
- Which command will allow you to verify the active DHCP server that has assigned an IP address to the router?
A. Router#show dhcp lease
B. Router#show ip dhcp lease C. Router#show ip lease
D. Router#show ip interface
A
- A. The command show dhcp lease will help you verify the IP address configured on the router, the DHCP server that served the lease, and the lease time in seconds.
33
Q
- Which statement is true about the Offer packet of DHCP?
A. The layer 3 destination is a unicast to the DHCP client.
B. The layer 2 destination is the MAC address of the DHCP client.
C. The layer 2 source is the MAC address of the server. D. The layer 3 source is a link-local address of the client.
A
- C. The DHCP Offer packet is a broadcast packet from the DHCP server to the DHCP client. The layer 3 packet and layer 2 frame are both broadcasts.
34
Q
- Which command will configure a DHCP relay agent on an interface to the DHCP server of 10.10.1.101?
A. Router(config)#ip dhcp server 10.10.1.101
B. Router(config-if)#ip dhcp server 10.10.1.101 C. Router(config-if)#ip relay-agent 10.10.1.101
D. Router(config-if)#ip helper-address 10.10.1.101
A
- D. The command ip helper-address 10.10.1.101 will configure the interface to become a DHCP relay agent. This command must be configured on the interface in which you want the DHCP relay agent to listen and respond
35
Q
- Which DHCP field helps a DHCP server decide which scope to serve to the DHCP
relay agent?
A. CIADDR B. GIADDR C. SIADDR
D. CHADDR
A
- B. The Gateway Address (GIADDR) field is filled out by the DHCP relay agent before the DHCP packet is sent to the DHCP server. This field helps the DHCP server decide which scope to send an Offer message back for.
36
Q
- Which port and protocol does the server use to await connections for DHCP?
A. TCP/68 B. UDP/68 C. TCP/67
D. UDP/67
A
- D. The DHCP server bind port of UDP/67 is used for awaiting connections from DHCP clients
37
Q
41. Which Windows command will allow you to see the DHCP server that has configured the client computer with an IP address? A. C:\>ipconfig B. C:\>ipconfig /all C. C:\>ipconfig /showclassid D. C:\>ipstatus
A
- B. The command ipconfig /all will display the generic information of IP, subnet mask, and gateway. It will also display the DHCP server that configured the client with an IP address
38
Q
- Which message is sent from the DHCP client to the DHCP server to confirm the
offer of an IP address? A. Acknowledgment
B. Discover C. Offer
D. Request
A
- A. The DHCP acknowledgment message is sent from the DHCP client to the DHCP server to acknowledge that the IP address offered will be used by the client.
39
Q
- What form of communications does a DHCP client use to initially acquire an IP address?
A. Layer 3 broadcast B. Layer 3 multicast C. Layer 3 802.1Q
D. Layer 3 unicast
A
- A. DHCP uses layer 3 broadcasts by sending packets to 255.255.255.255 for initial DHCP discovery
40
Q
- At what point of the lease time will the client ask for a renewal of the IP address from the DHCP server?
A. One-quarter of the lease B. One-half of the lease
C. Seven-eighths of the lease
D. End of the lease
A
- B. DHCP clients request a renewal of the lease halfway through the lease time of the IP address
41
Q
- Which statement is correct about the DHCP process?
A. The DHCP server is responsible for maintaining the life cycle of an IP address. B. DHCP uses multicasting between the client and server.
C. The DHCP client is responsible for maintaining the life cycle of an IP address.
D. The DHCP lease is negotiated between client and server.
A
- C. After the initial Discover, Offer, Request, and Acknowledge, it is the client’s responsibility to maintain the lease of the IP address. This includes release and renewal
42
Q
- Which transport protocol does DHCP use?
A. UDP B. ICMP C. TCP
D. RARP
A
- A. DHCP uses UDP as a connectionless protocol for the Discover, Offer, Request, and Acknowledge packets.
43
Q
47. Which command will allow you to diagnose DHCP relay agent messages on a router or switch? A. Router#debug dhcp B. Router#show ip dhcp detail C. Router#debug ip dhcp server packet D. Router#debug ip dhcp
A
- C. The command debug ip dhcp server packet will show the details of a DHCP relay agent conversation. It will detail conversation between the client and router and the router and the DHCP server
44
Q
- What is DHCPv6 used for when a network is configured for Stateless Address
Autoconfiguration (SLAAC)?
A. Stateful configuration of clients for IPv6 addressing
B. Configuration of clients with the IPv6 network IDs C. Configuration of clients with IPv6 options
D. Stateless configuration of clients for IPv6 addressing
A
- C. Stateless Address Autoconfiguration (SLAAC) allows for the client to learn the network ID and calculate a host ID that is unique. However, SLAAC is lacking the ability to configure options such as DNS time servers, etc. DHCPv6 allows for the configuration of these options when used in conjunction with SLAAC.
45
Q
- The DHCP server in the network went down. What happens to clients that have obtained IP addresses from the DHCP server?
A. They lose their IP address immediately.
B. They lose their IP address after one-half of their lease has expired.
C. They lose their IP address after seven-eighths of their lease has expired.
D. They lose their IP address after their entire lease has expired.
A
- D. They will lose their IP after their entire lease has expired. Until the lease expires, they will have functioning IP addresses.
46
Q
- Which command will configure a router as a DHCPv6 relay agent for a stateful DHCPv6 server?
A. Router(config)#ip dhcp server 2001:db8:1:2::2
B. Router(config-if)#ipv6 dhcp relay destination 2001:db8:1:2::2 C. Router(config-if)#ip dhcp server 2001:db8:1:2::2
D. Router(config-if)#ipv6 helper-address 2001:db8:1:2::2
A
- B. The command ipv6 dhcp relay destination 2001:db8:1:2::2 will configure the router interface to relay DHCP requests to 2001:db8:1:2::2. This command must be configured on the interface that is to listen for DHCPv6 requests
47
Q
- You need to configure a lease duration of 4 hours for a DHCP pool. Which
command will achieve this?
A. Router(dhcp-config)#lease 0 4 0
B. Router(dhcp-config)#lease-duration 0 4 0 C. Router(dhcp-config)#lease 4 0 0
D. Router(dhcp-config)#dhcp lease 0 4 0
A
- A. The command lease 0 4 0 will configure the DHCP pool for a duration of 0 days, 4 hours, and 0 minutes.
48
Q
- Which command will create an exclusion of 192.168.1.16 to 192.168.1.31 in the
DHCP pool?
A. Router(dhcp-config)#exclusion 192.168.1.16 192.168.1.31
B. Router(dhcp-config)#dhcp exclusion 192.168.1.16 192.168.1.31
C. Router(dhcp-config)#ip dhcp exclusion-address 192.168.1.16 192.168.1.31
D. Router(config)#ip dhcp exclusion-address 192.168.1.16 192.168.1.31
A
- D. The command ip dhcp exclusion-address 192.168.1.16 192.168.1.31 will configure an exclusion address range by specifying the low IP address and the high IP address. This command is configured from the global configuration prompt.
49
Q
- When configuring a DHCP pool, which option(s) will configure the client to boot
from a PXE server?
A. Router(dhcp-config)#option pxe 10.1.1.5
B. Router(dhcp-config)#option 66 10.1.1.5
C. Router(dhcp-config)#option 60 ascii PXEClient
Router(dhcp-config)#option 66 ip 10.1.1.5
D. Router(dhcp-config)#option 66 ip 10.1.1.5 Router(dhcp-config)#bootfile boot\x86\wdsnbp.com
A
- D. The command option 66 ip 10.1.1.5 sets the TFTP server to boot from. The command bootfile boot\x86\wdsnbp.com sets the bootfile on the TFTP server to boot\x86\wdsnbp.com. Some clients may need other options, such as option 60, which is the vendor class identifier.