Questions tagged [cidr]

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Check if IP Belongs to a CIDR

We have a list of CIDR's 1.10.10.0/24 5.154.0.0/16 5.181.219.0/24 23.90.68.0/24 31.40.214.0/24 I want to check if a IP for example : 23.90.68.56 belongs to any of the above CIDR's. If yes then we get ...
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AWS VPC Subnetting

I have a VPC created with a CIDR block of 10.10.0.0/16. I am trying to subnet that block into some /24's -- ie. 10.10.1.0/24 It wont let me. The error I get is: CIDR Address overlaps with existing ...
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How do I route all public traffic through Wireguard but not local traffic?

I know there's a series of CIDRs that I can use to cover all public CIDRs and leave out local CIDRs, but I cannot find this anywhere and I don't recall where I found it a couple of years ago when ...
1 vote
2 answers
90 views

Resource handler returned message: "The CIDR '10.0.1.0/22' is invalid

I'm getting this error while trying to create a VPC with a Subnet in CloudFormation. Subnet CREATE_FAILED Resource handler returned message: "The CIDR '10.0.1.0/22' is invalid. (Service: Ec2, ...
0 votes
1 answer
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What does 0.0.0.0/0 mean?

For example in an 'allow' statement in BIND or in Chrony config files. Does allow 0.0.0.0/0 mean allowing any clients or allowing no clients? My question isn't about the specific programs, but just ...
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1 answer
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"AWS CIDR is not within the CIDR ranges of VPC", but it is?

many questions on this, but this time doesn't seem as obvious as the others. I'm trying to split a VPC in two subnets. I start with VPC 10.0.0.0/24, 254+1 IPs, from 10.0.0.1 to 10.0.0.255 I create the ...
0 votes
1 answer
209 views

Is it possible to communicate between different CIDRs?

For example, there are two CIDRs in the same VPC on AWS. One of them is public and one is private. They are in the different segment. # Public Subnet CIDR 10.124.42.0/27 # Private Subnet CIDR 10.124....
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1 answer
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Can fail2ban-client tell me if an ip from a CIDR range is in a jail? [duplicate]

If I have a CIDR like 13.54.63.128/26 can fail2ban-client tell me if there's an IP in this range that's currently banned? Currently I'm doing: CIDR="13.54.63.128/26" nmap -sL -n $CIDR | awk '...
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2 answers
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Identifying subnet bits of network addresses with same CIDR [closed]

Say we have network addresses 10.10.10.252/30 and 10.10.255.252/30 and 10.255.255.252/30. They all have CIDR of 30. I realize all three subnets have two usable hosts. All three addresses have subnet ...
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Issues with Ubuntu Network Setup

Please, someone tell me whats up here, I am going bonkers, I have used multiple calculators etc, everything tells me the details in the image are correct but ubuntu just will not accept.
-1 votes
1 answer
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Banning an IP address

I banned an IP on my server, but I'd also like to ban using the CIDR method, e.g. IP/24. My questions are: How do I find the CIDR range of the IP address. When banning the range, if the user has a ...
4 votes
2 answers
3k views

What is a correct IP4 CIDR for AWS?

I am trying to create some new subnets and cannot get AWS to accept a CIDR IP4. I receive the message: Must be valid IPv4 CIDR. Nothing I try is accepted. What is a valid IP4 for this purpose, and why?...
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3 votes
4 answers
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AWS VPN Client connection to new VPC Endpoint is failing

I have set up a new VPN following the guide here. However when I try to connect to the VPN with the client i get an error "Connection failed. Try again." This happens every time. I opened the log file ...
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How to connect a VM to the Internet in VMware vCloud using a Network Gateway CIDR

I am familiar with managing servers and VMs that have their own IP address and network connection, but am now trying to host a VM in a VMware vCloud and am a newb for this. I have created the VM and ...
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1 answer
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Finding netid in CIDR [closed]

I am practicing questions related to CIDR and I have come across a particular question which I need some explanation. Can somebody please explain in detail how to answer this question. An address ...
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How to get range of ip addresses of current network

I am using AWS to host my website, recently I've been getting a lot of background noise on the server (bots trying to backdoor, etc.). I would like to limit access of my website to just our worksites ...
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1 answer
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What is the VPC accepted address and why [duplicate]

i am trying to create a vpc but the ip i am providing is not accepted which is 192.168.1.1/16 but aws says i can use the following range if i set to 192.168.0.0/16 it works , i guess to an extent ...
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Is it possible to change CIDR network flannel and Kubernetes

Is it possible to change CIDR network flannel on running Kubernetes cluster? If yes what will happen with the launched pods? Thanks
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1 answer
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What if my public address is same as one of the IP address in my AWS VPC CIDR Block? [closed]

My public IP address (of my personal computer) from which I access the internet ranges from 112.110.x.x. For experiment, I created a VPC in AWS and chose the CIDR block as 112.110.0.0/16. In the route ...
0 votes
1 answer
758 views

Allowing external access to bastion hosts on aws

I am trying to create a few bastion hosts in my VPC on aws to connect to my databases that are located in a private subnet. I am using this aws Quick start. I understand the basics of CIDR blocks ...
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2 answers
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Subnet CIDR Scheme

I am redoing some VPC work that my predecessor did. I haven't setup a lot of networks, so I wanted to double check what I think makes sense isn't breaking some rule that I'm not familiar with. What ...
3 votes
1 answer
934 views

Does 0.0.0.0/7 represent the same range as 1.0.0.0/8?

The range of 0.0.0.0/7 is 0.0.0.0 - 1.255.255.255. The range of 1.0.0.0/8 is 1.0.0.0 - 1.255.255.255. AFAIK, 0.0.0.0/8 (0.0.0.0 - 0.255.255.255) is not usable. So, do these represent the same range ...
0 votes
2 answers
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AWS queries regarding subnetting and routing

I have some queries regarding AWS setup please clarify. I have created a VPC with CIDR 172.16.0.0/16 which is a private range of IP's. In my route table, I routed all the traffic from this range. ...
3 votes
7 answers
1k views

What does the netmask in an IP address actually tell you?

There are several questions out there asking what the CIDR netmask is, and how it's calculated. But after reading all the top answers, I'm still left wondering, how does the netmask let us distinguish ...
0 votes
1 answer
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What IP addresses are included in a subnet "range"?

I'd like some help understanding subnets (CIDR). I'm using a tool to check if an IP is in an acceptable range given a CIDR address. When I input an IP address (12.245.105.190) and check it against ...
1 vote
0 answers
543 views

Adding exception to nginx HTTP basic authentication based on being on the local network

I'm running an installation of a webapp running on a self-hosted server which is on my main network along with all our company PCs and a couple of other servers. We've decided we want to add HTTP ...
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1 answer
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fail2ban - Filter IPs by cidr blocks

I'm using fail2ban 0.10.0 and with it I'm able to trigger some actions to block bruteforce attempts from a given single origin (with the HOST tag). But suppose someone has control over an entire /24 ...
0 votes
1 answer
37 views

How will a router handle this destination address?

Let's say I have a router with three interfaces. Interface #1 is 10.x.x.x /8 Interface #2 is 142.100.48.x /20 Interface #3 is 142.100.56.8 /21 I'm trying to send a file to [dest]142.100.57.5 from [...
1 vote
1 answer
120 views

How can destination addresses 132.148.77.28 and 132.148.77.28/32 be use different network interfaces for routing?

The output of netstat -rn on my FreeBSD virtual machine shows that: Internet: Destination Gateway Flags Netif Expire default 10.195.51.254 UGS vtnet0 10....
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1 answer
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Cannot get HTTPD 2.4 to start when using the Require IP command for access control

This was intended to be a comment on a similar question but since Stack is so restrictive about comments I'm reposting it as they want it: : Here's the documentation: http://httpd.apache.org/docs/2.4/...
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AWS Reserved IP addresses [closed]

I have multiple VPC in my account and I created most of VPC using subnet 10.0.0.0/8 or 192.168.0.0/16 or 172.16.0.0/12 subnet blocks. I am exhausted with my range due to not optimizing the IP ...
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1 answer
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Using a AWS VPN for client access to an internal web-application

I'm trying to connect a client's network to our AWS data-centre, to allow access to a (previously publicly available) internal web-application. At the moment we've got the VPN set up with dynamic ...
4 votes
1 answer
6k views

Why is my AWS instance's private IP outside of the subnet's range?

I'm trying to launch an instance with the private IP address 172.31.32.101 using Terraform in my default VPC (CIDR 172.31.0.0/16), in the eu-west-1a subnet that has the CIDR 172.31.32.0/20. I can ...
0 votes
1 answer
1k views

Connecting two AWS VPC Regions of the same CIDR range

Let say I have two VPC's (VPC-A with 10.50.0.0/16 and VPC-B with 10.50.0.0/16) in AWS with same conflicting/overlapping CIDR ranges in my AWS account. I already have the two VPC's fully functional ...
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Can foreman handle nested subnets?

In Foreman 1.8 one can manage subnets through the web-interface at Infrastructure > Subnets. However, when I add a /24 (e.g. 10.10.0.0 with a subnetmask of 255.255.255.0), I cannot add anything less ...
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2 answers
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What's the difference between .0/32 and .1/24 in CIDR? [closed]

We're specifying CIDR addresses in AWS rules, and I came across something I don't understand. /32 means one single address. So 10.0.0.0/32 means only the single address 10.0.0.0. But an address ...
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55 votes
6 answers
52k views

What is the recommended CIDR when creating VPC on AWS?

I have been creating AWS VPCs and I am wondering if there is a recommended CIDR value when creating VPCs. What are the factors that I must consider when choosing a CIDR and does the CIDR value affect ...
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2 answers
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Google IP Address Ranges for incoming SMTP [duplicate]

Essentially I'm answering my own question here, but want to provide this info to anyone else who might need it. I need all the valid IP address ranges for Google Apps mail servers. I'm configuring a ...
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16 votes
5 answers
3k views

Are Cisco admins expected to understand classful networks?

While studying for the CCENT exam, my reference materials have made an alarming number of references to class A/B/C networks. Thankfully they just treat Class A/B/C as shorthand for /8, /16, and /24 ...
-2 votes
1 answer
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SOHO Routers and Non-Standard CIDR Blocks [closed]

I recently learned about private networks. From what I understand there are three address ranges for use in private networks: 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 If this is the case, then why on ...
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2 answers
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Why does the Cisco RV180 not let me use a 255.255.254.0 subnet mask with a 192.168.2.1 LAN IP address?

I'm a Sysadmin for a tech company. We have a Cisco RV180 gateway device. We are at our breaking point for IP addresses, so we are changing from a /24 to a /23 subnet to allow for double the devices. ...
0 votes
1 answer
412 views

Using a CIDR range as a Routed Subnet?

I have a /29 subnet assigned by my ISP, with an SonicWALL office router and a Cisco voice router hooked up to a 'net-rail' of sorts with untagged VLAN switch ports connecting my ISP router's output ...
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1 vote
2 answers
238 views

How to reserve first 32 hosts in IP address range

I am using NoDogSplash which is a captive portal, meaning it redirects your packets and forces you to authenticate before you can access the Internet. It does this in an isolated 10.0.0.0 network. Now,...
2 votes
2 answers
3k views

How do I divide a network into smaller subnets using a single Layer 3 switch?

I have had trouble searching for help on this one, as most searches for VLSM, CIDR and layer 3 switching bring back very basic questions posted by students just starting their CCNA. I have a batch of ...
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4 votes
2 answers
332 views

Is this IPv4 and subnet combination public or private? [duplicate]

Possible Duplicate: How does IPv4 Subnetting Work? I thought I understood this but I am momentarily confused. Here is an example: Are all IPv4 addresses from 192.168.0.0 to 192.168.255.255 in ...
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4 votes
0 answers
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How to support VRF in Netflow Collector?

I am somehow able to analyze netflow packet using my own netflow collector (build in python). It works for certain ip and CIDR(Classless Inter Domain routing), definitely not overlapping. What is the ...
user avatar
1 vote
2 answers
193 views

smaller CIDR network on larger Class C network

I have a network: 192.168.31.0/24 and computers on the network have static IPs 192.168.31.* I'd like to segregate 5 of those computers (say 192.168.31.201 - 192.168.31.205) and put them behind a ...
13 votes
2 answers
12k views

Grepping for CIDR ranges

From time to time I want to grep CIDR ranges out of my Apache log files. This is easy for ranges that fall on the natural boundaries (/8, /16 and /24) but not so easy for other ranges such as /17 and ...
3 votes
1 answer
2k views

Subnetting into 6 CIDR/24 network and 2 CIDR/27 networks?

I am revising some questions for an exam and one of the questions was provide the ip numbers and a diagram for a company which has 3 branches. Paris/Berlin/Cairo (random locations I know) Now I belive ...
7 votes
2 answers
4k views

If I change a router's subnet mask to one that includes the old one, will the hosts with the old configuration still work?

Currently I have a router that is addressed as 10.2.1.1 on a 10.2.1.0/24 network. All of my hosts have default gateway 10.2.1.1 with mask 255.255.255.0. I want to know: if I change my router to 10.2....