15
votes
5answers
1k 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 ...
-4
votes
2answers
180 views

Exercise regarding public IP address and its “class C” [closed]

An exercise I am doing asks the following:- Identify what your public IP address is. Using public information sources, see what you can learn about your IP. If you don'ʹt find anything on your ...
2
votes
2answers
451 views

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
1answer
155 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 ...
2
votes
2answers
796 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 ...
4
votes
2answers
163 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 ...
1
vote
2answers
118 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 ...
3
votes
1answer
832 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 ...
6
votes
1answer
769 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 ...
1
vote
1answer
236 views

Openvpn: iroute for all theoretically reachable [public] IPs

I am testing the creation of an enforced default route of only public IPv4 space via OpenVPN. OpenVPN does not support 'iroute 0.0.0.0 0.0.0.0' out of the box, because it contains code that rejects ...
0
votes
1answer
80 views

subnetting a class c on a cisco 3825

I have a class C that I want to better understand before I implement a change. Right now, ip address 192.168.0.1 255.255.255.192 ip address 192.168.0.65 255.255.255.240 secondary So, where is ...
1
vote
6answers
212 views

Trouble subnetting a network

I have the network address 160.80.0.0/24 and have to subnet things like this: How would I subnet this network to accomodate such a huge number of hosts? :D Any guidance for a newbie? I've already ...
0
votes
6answers
316 views

Is there a tool for subnetting for free?

I'd like a program that I can write in an IP address and give it the Subnet mask and have it divide the networks in C level networks. Thanks. Something that I can download please, not a website.
5
votes
4answers
2k views

Linux Command line tool to work with netmasks / CIDR notation

I'm terrible at working out network subnets in my head. Is there some command line tool for linux (ubuntu packages a plus), that lets me put in 255.255.255.224 and it'll tell me that is a /27?
21
votes
6answers
9k views

CIDR for Dummies

I understand what CIDR is, and what it is used for, but I still can't figure out how to calculate it in my head. Can someone give a "for dummies" type explanation with examples?