Consider the following diagram: A,B,C and D are subnets, R1, R2, and R3 are routers. Default signifies the entire rest of the internet. All 4 subnets each contain the same number of hosts. Consider the following routing table at R3: CIDR Mask Link 0.0.0.0/0 L4 128.4.6.0/24 L3 128.4.8.0/24 L5 1. If 128.4.6.0 is in A, what is the routing table at R1? 2. The ISP that owns all these networks is short on IP addresses, so they use a NAT router for R2. How many public IP addresses will C and D use together assuming they use as many private 10.X IP addresses as they can? How many total public IP addresses will be used by the entire network? Why doesn’t the ISP care about how many private IP addresses are used? 3. Fix R3’s routing table now that we are using NAT: 4. A node in C is given the IP address 10.0.0.1 and only sends and receives packets on port 1234. A packet destined for this node reaches R2 with a source of (IP=128.4.6.6, Port=3000) and destination of (IP=128.4.8.0, Port=10000). When C replies to this packet, what will the source and destination (Src port, src IP, dest port, dest IP) on the reply look like when it leaves C? What about when it leaves R2? 5. If the ISP switched the network over to entirely IPv6, what would they likely change about the network from question 16? (not including the obvious different address formats) If there are some routers along the path to the rest of the internet that use IPv4, can the two endpoints still use IPv6 to communicate? How?
Consider the following diagram:
A,B,C and D are subnets, R1, R2, and R3 are routers. Default signifies the
entire rest of the internet. All 4 subnets each contain the same number of hosts.
Consider the following routing table at R3:
| CIDR Mask | Link |
| 0.0.0.0/0 | L4 |
| 128.4.6.0/24 | L3 |
| 128.4.8.0/24 | L5 |
1. If 128.4.6.0 is in A, what is the routing table at R1?
2. The ISP that owns all these networks is short on IP addresses, so they
use a NAT router for R2. How many public IP addresses will C and
D use together assuming they use as many private 10.X IP addresses as
they can? How many total public IP addresses will be used by the entire
network? Why doesn’t the ISP care about how many private IP addresses
are used?
3. Fix R3’s routing table now that we are using NAT:
4. A node in C is given the IP address 10.0.0.1 and only sends and receives
packets on port 1234. A packet destined for this node reaches R2 with
a source of (IP=128.4.6.6, Port=3000) and destination of (IP=128.4.8.0,
Port=10000). When C replies to this packet, what will the source and destination (Src port, src IP, dest port, dest IP) on the reply look like when it leaves C? What about when it leaves R2?
5. If the ISP switched the network over to entirely IPv6, what would they
likely change about the network from question 16? (not including the
obvious different address formats) If there are some routers along the path
to the rest of the internet that use IPv4, can the two endpoints still use
IPv6 to communicate? How?
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