Twelve questions on the whole course, each with an explanation.
Intermediate · 10 min read
Technical definition
IP services are the supporting services a Cisco network runs alongside forwarding: NTP keeps clocks in step, DHCP hands out addresses, SNMP and Syslog report on devices, TFTP and FTP move configurations and IOS images, and QoS decides which traffic goes first when a link is congested.
Twelve questions on the whole course, using the lab network from the lessons: PC1 and SW1 in VLAN 10 (192.168.10.0/24) behind R1, R1's Gi0/1 linked to R2 over 10.0.12.0/30, SRV1 at 192.168.20.10 behind R2 (DHCP, Syslog, SNMP manager, TFTP and FTP), and R1's Gi0/2 at 203.0.113.2 toward the internet, where the NTP server 198.51.100.10 sits. If you get one wrong, the explanation names the lesson to go back to.
Predict · scenario 1
1. show ntp associations on R1 shows '*~198.51.100.10 ... st 2' and '+~203.0.113.1 ... st 3'. Which server is R1 synchronised to, and what is R1's stratum?
Predict · scenario 2
2. R2 has ntp authenticate, ntp authentication-key 1 md5 Ntp-Lab-Key, ntp trusted-key 1 and ntp server 10.0.12.1 key 1. R1 has ntp authentication-key 1 md5 Ntp-Key-Lab and ntp trusted-key 1. NTP worked before authentication was added. What happens now?
Predict · scenario 3
3. R1's Gi0/0 has ip helper-address 192.168.20.10, and R1 can ping SRV1. SRV1 has a DHCP pool only for 192.168.20.0/24. What happens when PC1 in VLAN 10 asks for an address?
Predict · scenario 4
4. show ip route on R1 contains S* 0.0.0.0/0 [254/0] via 203.0.113.1, but nobody typed an ip route command. Where did the route come from?
Predict · scenario 5
5. R1 has logging host 192.168.20.10 and logging trap errors. A link fails and R1 generates %LINK-3-UPDOWN and %LINEPROTO-5-UPDOWN. Which messages reach SRV1?
Predict · scenario 6
6. A log line reads: *Oct 6 14:22:31.418: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down. What do the leading * and the 3 tell you?
Predict · scenario 7
7. SRV1 polls R1 with SNMPv2c without problems, and R1 has snmp-server host 192.168.20.10 version 2c Lab-R0-Str1ng. When Gi0/2 goes down, no trap arrives. Which command is most likely missing on R1?
Predict · scenario 8
8. On R1 you type: copy ftp://192.168.20.10/c2900-universalk9-mz.SPA.157-3.M8.bin flash:. What does the command do?
Predict · scenario 9
9. After copying a new image, configuring boot system flash: lines, saving and reloading, R1 stops in ROMMON. What is the most likely cause?
Predict · scenario 10
10. During the evening backup, calls still break up. show policy-map interface GigabitEthernet0/1 on R1 shows the VOICE class (match dscp ef) packet count not increasing during a call. What is the most likely cause?
Predict · scenario 11
11. A queue on R1 is filling, and WRED sees packets marked AF21 and AF23. Which does it start dropping first?
Predict · scenario 12
12. R1's Gi0/2 runs at 1 Gbps, but the ISP contract is 100 Mbps and the ISP drops anything above it. Bursts from R1 are being lost. What should R1 do?