IP addresses. Company X and Company Y both connect to the same ISP. Company X is

Question

IP addresses. Company X and Company Y both connect to the same ISP. Company X is assigned the prefix 121.77.0.0/18 and Company Y is assigned the prefix 121.77.64.0/18. The ISP has a single 3-port router: port 1 connects to Company X, port 2 connects to Company Y, and port 3 connects to the rest of the Internet. Draw and complete (as best you can) the contents of the forwarding table in the ISP's router. What aggregated prefix does the router advertize to the rest of the Internet so that packets can reach Company X and Company Y?

Explanation / Answer

1) Routing Table – The routing table for ISP should be in the following manner. Mask 18 is specified for each IP. Hence Genmask is 255.255.192.0

2) The aggregate prefix for each IP can be obtained by converting IP to binary number and applying the mask.

For Company X: The given IP is

121.77.0.0/18 -

01111001.01001101.00000000.00000000

For Company Y: The given IP is

121.77.64.0/18 -

01111001.01001101.01000000.00000000

The bolded part is the aggregate prefix obtained from the given IP by applying mask.

Destination Gateway GenMask Interface 121.77.0.0 CompanyX GatewayIP 255.255.192.0 1 121.77.64.0 CompanyY GatewayIP 255.255.192.0 2 0.0.0.0 default Gateway IP 0.0.0.0 3

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.