Overview

Chapter 5, 6 and 8. Necessarily, the basics of earlier chapters will be included in order to make meaningful questions.

There is a challenging BONUS question on NAT routing (similar to what was on exam 2).

Scenarios

• Know how to find the MAC address, IP address and netmask (and convert it to CIDR format) in the output of ipconfig.

  eth0      Link encap:Ethernet  HWaddr 00:D0:59:DA:67:27
            inet addr:10.1.1.11  Bcast:10.255.255.255  Mask:255.0.0.0
            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
            RX packets:7682 errors:0 dropped:0 overruns:0 frame:0
            TX packets:3336 errors:0 dropped:0 overruns:0 carrier:0
            collisions:460 txqueuelen:100
            RX bytes:4163078 (3.9 MiB)  TX bytes:501341 (489.5 KiB)
            Interrupt:11 Base address:0x6000
  

• For a simple path as shown, understand which header fields in the TCP, IP, and Ethernet headers will change as the frame traverses the links.

  A----R1----R2------R3-------R4------R5-------R6-------B
  

• For this network, a solution to the Chapter 6 Problem 14 you did (with truncated MAC addresses of 16 bits), you will be told to work with a frame going from one specific host to another host. You will have a chart with a line for each link the frame traverses. For each line in the chart you will be asked to fill in the MAC, IP, and TCP Port addresses. The nature of how it is asked will mean that there are no ambiguities.

  The chart will look like this except that it may have more or less lines and the link specifics will be filled in.

   ----------------------------------------------------------------------------
   | Link |Dest MAC|Src MAC |Dest IP       |Src IP        |Dest Port|Src Port |
   ----------------------------------------------------------------------------
   |????  |        |        |              |              |         |         |
   |      |        |        |              |              |         |         |
   |--------------------------------------------------------------------------|
   |????  |        |        |              |              |         |         |
   |      |        |        |              |              |         |         |
   ----------------------------------------------------------------------------
  

  

  There are also questions about how an ARP frame will function and the contents of the forwarding tables in switches.

  Other minor scenarios

  • The SHA-256 hash of a stored password is kept in the database on the server. The user client sends a hash of the password to the server. The hash the user sends is compared to the has on the server. What does the comparison tell us?
  • A frame has a destination IP address of: 255.255.255.255
  • The following are installation scenarios. Consider what manual configuration must be done vs. what happens just by plugging in.
    • A new Ethernet switch is installed and hosts are plugged in. With and without VLANs.
    • A set of inter-connected Ethernet switches is installed in a building with one switch per floor with trunking. The entire building is the same subnet.
    • A router is installed which has a link from this AS to another AS. Policy must be implemented to stop unwanted traffic from traversing this AS.
    • A new router is installed on a company campus. OSPF is used as the routing protocol. Link weights are carefully chosen according to complex criteria.
    • A new computer is installed and the Windows default for IP of using DHCP to find the IP address is left in place. The computer uses Ethernet and is attached to a switch.
    • A computer using DHCP is moved to a different subnet.
    • A server has a fixed IP address because it is known to the outside world and DNS points to its IP address. The server is moved to a place where it will be on a different subnet.
  • A host has learned via iBGP that there are 2 border routers in the AS, each of which has a path to the destination host.
  • A router on the border of an AS learns via eBGP that there are two paths to particular AS.
  • What kinds of filtering can be done in a stateless firewall.
  • What kinds of filtering can be done in a statefull firewall.