LPI Linux Certification in a Nutshell, 2nd Edition

Networking Configuration (Topic 2.205)

Review Questions

1. You have learned that a system does not currently specify the correct default gateway. The correct default gateway address is 192.168.2.1. What commands would you issue to delete the existing gateway address and add a new one?

2. What command would you issue to assign a second IP address of 192.168.2.55 and a netmask of 255.255.255.0 to your eth1 card?

3. The arpwatch daemon has discovered several "flip-flops," implying that ARP poisoning has occurred on your network. Where can you read the alerts sent by the daemon?

4. A remote office has had to swap out a failed NIC in its Linux router. This router must work with an ISP's cable modem to allow the remote office to access the Internet. However, the ISP's cable modem recognizes only the MAC address of the failed card. What command can help you solve this problem?

5. You have tried to use tcpdump to capture packets and analyze them. However, tcpdump captures only the first few parts of the packet by default, and you want to capture and display the entire packet. You also want to save the capture into a file named cap1.cap. What command allows you to do this?

6. You have just used the netstat command, and have read the following entry:

   tcp    0   6 64-128-206-189.ge:53208 mail1.oreilly.com:imap2 ESTABLISHED
   What system has opened port 143?

Answers

1. Run two commands:

   # route del default gw
   # route add default gw 192.168.2.1

2. Run:

   # ifconfig eth1:1 192.168.2.55 netmask 255.255.255.0

3. arpwatch alerts are usually mailed ...