For each IP Address, please identify the CIDR NetBlock for the IP Address, as we

Question

For each IP Address, please identify the CIDR NetBlock for the IP Address, as well as the ASN # for organization that hosts this IP Address. Use the “ASN.Cymru.com” for finding the ASN number. Remember that sometimes you will need to CALCULATE the CIDR Netblock based on the network range provided in the WHOIS information

(The “Question” for each will be the Phishing IP address. Each IP is used for two questions,

“What is the Autonomous System Number for the IP Address ______________?”

(where the answer will be whatever is in the ASN Column”)

The second Question will be:

“What is the CIDR Netblock address for the IP Address ___________________?”

(Where the answer will be whatever is in the CIDR Column)

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1. What is the CIDR Netblock address for the IP Address 185.57.82.61?

2. What is the Autonomous System Number for the IP Address 116.0.23.207?

3. What is the CIDR Netblock address for the IP Address 116.0.23.207?

4. What is the Autonomous System Number for the IP Address 203.143.20.8?

5. What is the CIDR Netblock address for the IP Address 203.143.20.8?

Explanation / Answer

CIDR stands for Classless Inter Domain Routing. It is used for allocating IP addresses and IP routing. Using this method, we can remove the classes of IP and designate a range of IPs. CIDR address is denoted using the starting IP address followed by a / and a number. This number is based on Variable length subnet masking (VLSM) which is used to create networks across classes.

CIDR address is in the format of a.b.c.d/n where using n, we can calculate the number of IPs in the CIDR block. The value of n ranges from 0 to 32. Number of IP addresses in the CIDR block is calculated using 2(32-n). Therefore, if n = 32, number of IP addresses in the CIDR netblock is 2(32-32) = 20 = 1 and if n = 0, number of IP addresses in the CIDR netblock is 232 = 4294967296.

If we have to Calculate CIDR for a single IP address, the value of n is always 32. For CIDR netblock, we need to get the range using whois command and then calculate the address by taking the difference between two IPs

1. 185.57.82.61

CIDR:   185.57.82.61/32 CIDR Netblock: 185.57.80.0/22

ASN: 60118 AS Name: ALISTAR-AS, RO

2. 116.0.23.207

CIDR:   116.0.23.207/32   CIDR Netblock: 116.0.16.0/21

ASN: 9280   AS Name: CIA-AS Bucan Holdings Pty Ltd, AU

3. 203.143.20.8

CIDR:   203.143.20.8/32   CIDR Netblock: 203.143.0.0/18

ASN: 5087 AS Name: LANKA-COM Lanka Communication Services, LK

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