CS301 F2006 hw#2

Goal:

Learn about IP address.
Learn how end host routing works and basic commands for routing table, arp cache table, and network interface.
Learn how to interpret the IP classless notation and routing table entries.
Learn how to partition a subnet and assign gateway address.

Assignment Date: 9/11/2006
Due Day: 9/18/2006
Related Material: http://cs.uccs.edu/~cs522/intro/pcnetsetup/pcnetsetup.htm; Chapter 5.6.
Description:

Problem 1. Classless Address Notation and Routing. Chapter 5. Question 43.
Problem 2.a. Network Address Translation. Chapter 5. Question 44.
Problem 2.b. With NAT, can we still claim that 1) the destination address of IP packets will not be changed end-to-end? 2) every IP address uniquely idenfites a machine worldwide? Please brief explain and give an example.
Problem 2.c. lPv6 uses 16-byte addresses. If a block of 1 million addresses is allocated every nanosecond, how long will the addresses last?
Problem 3. IP Address and Routing.
Given the following routing table on arbor.uccs.edu.
arbor.uccs.edu> netstat -rn
Kernel IP routing table
Destination   Gateway       Genmask       Flags MSS Window irtt Iface
128.198.160.0 0.0.0.0       255.255.224.0 U     0   0      0    eth0
128.198.80.0 0.0.0.0       255.255.255.0 U     0   0      0    wlan0
169.254.0.0   0.0.0.0       255.255.0.0   U     0   0      0    eth0
127.0.0.0     0.0.0.0       255.0.0.0     U     0   0      0    lo
0.0.0.0       128.198.160.1 0.0.0.0       UG    0   0      0    eth0
From the first entry of the routing table, it indicates arbor located in a wired Ethernet subnet with IP address 128.198.160.0 and genmask (or called netmask) 255.255.224.0. The second entry indicates arbor also has wireless LAN card on a subnet identified with 128.198.80.0 and genmask 255.255.255.0.

What is the equivalent Classless IP addess notation for the wired Ethernet subnet?
What is the equivalent Classless IP address notation for the wireless subnet?
How many IP addresses can be assigned to machines in this wireless subnet (assume one is used by the router for the grateway interface, one used for broadcast, and one used for identifying the subnet itself)?
What command(s) you use to find out the MAC address of the gateway interface for 128.198.160.0 subnet?

On blanca, the /etc/resolv.conf file shows the following entry

search uccs.edu eas.uccs.edu
nameserver 128.198.160.64
nameserver 128.198.160.66
nameserver 128.198.1.250

The search line indicates the domain name(s) to attach to a local name such as sanluis for DNS name lookup.
The three nameserver lines indicate the primary DNS server used by blanca is 128.198.160.64, the secondary DNS server is 128.198.160.66 and the tenary DNS server is 128.198.1.250.

For DNS query, blanca will first try to send it to 128.198.160.64. In that DNS query message, what is the source IP address, the destination IP address, the source mac address, the destination mac address? What commands you used to find out those information without using ethereal?

Assume the 128.198.160.64 was shutdown for maintenance so is the 128.198.160.66. Both DNS queries will fail. Blanca will try the 3rd DNS server 128.198.1.250. In that DNS query message to 128.198.1.250, what is the source IP address, the destination IP address, the source mac address, the destination mac address?

Note that the gateway will forward the DNS query to 128.198.1.250 over its network interface connected to the 128.198.1.0/21 subnet, say 128.198.1.1. The frame sent by 128.198.1.1 interface will contain IP packet sent by arbor. Compare the frame received by the gateawy from blanca with the related frame to be sent by the gateway to 128.198.1.250,

Does the gateway (router) change the source and destination IP addresses of the IP packets passing by? Explain (Note that there are two cases, one involves with network address translation, NAT).

Give an example where a gateway may change the source and destination IP addresses of packets passing by.

Does the gateway (router) change TTL field in the IP header of packets passing by?

Does the router repeat the source and destination MAC addresses of the incoming frame in its outgoing frame?
If this is the IP packet destined to 129.42.19.99 (ibm.com), will the intermediate routers change any IP header fields?

Homework #2. IP address and End Host Routing. Due 9/18/2006