.:: Some IP Address related questions? ::.

[enoonmai]

Well, no one has posted this information so far, but the Windows Messenger service is routinely exploited by spammers to send advertisements via it. Microsoft recommends that you turn it off and if you are using Windows XP SP2, it will be disabled by default when installation completes. The message is usually started when a program runs the

net send * "<message>"

command and you get a window with
Messenger Service
Message from source to yourcomputername on date time
Message Text

Go to services.msc, stop the service and then set its startup type to Disabled. For more info, refer here:

*support.microsoft.com/default.aspx?scid=KB;EN-US;Q330904

 

[valtea]

talking abouty dns and ip is i install a web browser in one of the client in a cyber cafe (all having same external ip)
i can access the site by *internal.ip/
Is there any way that i can ppl from outside see the site?

 

[digen]

Web browser?eh? You mean a server right?

Could you elaborate a bit more like you network topology? How many computers?Since you say you get one external IP, which is the computer that is acting as the host for sharing the internet connection? or do you have a NAT router?or some sort of other translation?
Which server have you installed?

In your case to publish a site you need to host the site on the main "host" computer or in case you are behind a NAT router you need to port forward to a internal IP.
So it would be better if you could provide some details.

 

[enoonmai]

Digen, I think what's he trying to say is that he installed a webserver on a computer in a local network with a private IP address and wants to know if people outside the computer can access it.

@valtea: Well, it depends, if its purely a internal server that is firewalled, and does not communicate with the Internet, then no. If the server is communicating with the Internet, you can find out its "external" (as you put it) IP address by going to www.ipchicken.com and then finding your site's public IP address and posting it on a forum/discussion board so that people can access the server. However, if you do not publish the IP address of that computer in puiblic, unless someone actually knows there is a webserver at that address, they cannot access it, in fact, they wont even know about its existence.
However, be warned that doing this and putting a webserver up without a firewall and properly configured rules in place is inviting unnecessary trouble for yourself. Hackers armed with port scanner programs and aware of vulnerabilities with your webserver software can use it to mount attacks on your own networks or on other networks, especially if you have a high-speed connection.

 

[Deep]

net send "username" message ???
i thot u always use IP or the computer netbios name

username is for when the pc's are connected to a domain AFAIK !!

so for sending a msg over lan u need to have messenger service running on any/all pc's which will be partaking in it and then use for eg.

net send 192.168.0.1 "hello how are you"

quotes are required if u use spaces in your message

and dun worry afaik its ur isp sending u those msgs
and usually ISP's use NAT services . so u use a different private ip address which is translated to a public ip address via NAT
this is how they protect your pc from incoming attacks .
however u are still prone to attacks from within the lan

deep sir am i right this time ?

righto sir

cheers
Deep

 

[tuXian]

I tried to understand CIDR but unable to comprehend it properly can any one of you elaborate on it plz

 

[Deep]

hi,
to be frank i just know basics of these kind of stuff but a simple query in google gave me this site..

*public.pacbell.net/dedicated/cidr.html

they have explained things very well..

Deep

 

[enoonmai]

CIDR, well, its pretty simple.

Take an IPv4 address of the form xxxxxxx:Xxx. There are 5 classes of IP addresses from A through E. And each address has two parts - a network part and a node/host part.

A Class A IP address' first bit is always 0 and the next 7 bits identify the network. The last 24 bits (the three dotted decimal numbers) are assigned to host addresses. Which translates to addresses between 1.0.0.0 to 126.0.0.0, leaving a total number of 16,744,214 unique hosts/nodes.

A Class B address has 10 as the first two bits. The first 16 bits identify the network and the last 16 bits identify the nodes, so this IP address is neatly split halfway between networks and nodes. IP addresses for this class start from 128.1.0.0 to 191.254.0.0 and can accomodate 65,534 hosts.

A Class C address has 110 as the first three bits, with the next 21 bits being the network address and the last octet is the node part. So we have IP addresses from 192.0.1.0 to 223.255.254.0 and can accomodate 254 addresses.

A Class D address has the first four bits as 1110 and is usually used for multicasting and has an address range from 224.0.0.0 to 239.255.255.254.

Class E is reserved for research and is not available for use on the Internet.

The problem comes when assigning IP address blocks to users that request them. If a company needs 300 IP addresses, they cannot go in for Class C, obviously and class B is too much, wasting 65,234 addresses. If they go in for two Class C addresses, they end up creating two domains within the same company.

To overcome this problem, the CIDR was developed. What it does simply is that enables you to use subnet masks to customize the length of the network and node addresses. So instead of the rigid 8/16/24 bits that the previous assignments used, CIDR allows you to use any bit assignment from 13 to 27 as a "prefix" on the IP address, specifying how many bits are used to specify the network address. A CIDR address is usually written as a standard IP address along with information on the prefix. So the address would usually be something like:

xxx.xxx.xxx.xxx/AB where AB is the CIDR "prefix"

So, a prefix of /27 would mean that 27 out of the 32 bits are used for the network address and the remaining 4 bits are used for the hosts, allowing you to use that address for 32 hosts. So, what usually happens is that your ISP is allotted a CIDR block depending on their size, so (just an example) while VSNL would be allotted a /13 block prefix, they would in turn allot /15 or /18 blocks to ISPs like Sify, etc. who in turn allot it to resellers, who in turn allot it to you, etc. Its not the exact way its done, I was just giving you an example.

So, you would use your CIDR block to calculate addresses for your organization. So, if you are allotted an address like, say, 10.0.0.12, and you wanted to run 1000 computers on that IP addressing scheme, you would pick the CIDR prefix of /21 that allows you 2048 hosts, then you would have a subnet of 255.255.248.0 and a total number of 8192 subnets and 2048 nodes per network. For a great subnet calculator, visit this page here:

*www.subnetmask.info/

Hope that clears things up a little.

 

[digen]

Just as I was thinking of posting a long post comes your detailed reply.
^Couldnt have put it much better.Nice !!

 

[theraven]

yeah whats with that man?
suonds soo much like VLSM !
or is it that CIDR uses VLSM! hmmmm

 

[valtea]

well enoonmai you got me right.

The cybercafe is running windows 2000 as the server (in which the modem is installed) and we share internet connection of the win 2k machine to the clients using XP and 98.
i have installed apache in one of the win98 machine.
There are no firewalls/router as such

 

[digen]

Hmm dude install the server on the windows 2000 machine.I hope not wrong here,please do correct me if you feel so.
Since you dont have a router or any other sort of translation that could port forward & map it to any internal host you want,you'll have to install the apache server on the windows 2000 machine to get it online.

By any chance you on dial-up dude?

 

[tuXian]

My website site is hosted on a server which have more than 300 sites hosted. Therfore the site IP is shared.

Is there a way that if I type the IP in the address bar (appended with something extra like username or something) the website should load.

One more question [though I have it pasted in my siggy! LOL ]:

Does typing of IP directly loads the site faster avoiding the DNS overhead?

 

[Deep]

My website site is hosted on a server which have more than 300 sites hosted. Therfore the site IP is shared.

Is there a way that if I type the IP in the address bar (appended with something extra like username or something) the website should load.

One more question [though I have it pasted in my siggy! LOL ]:

Does typing of IP directly loads the site faster avoiding the DNS overhead?

generally you can visit site by

*YourIPHere/~YourUserName/

that is if cpanel is there and that option is enabled...

2nd question's anwer...

Nothing like that...both will load at same time...

Deep

 

[enoonmai]

One more question [though I have it pasted in my siggy! LOL ]:

Does typing of IP directly loads the site faster avoiding the DNS overhead?

I dont suppose you came up with the info in your siggy yourself. But yes, it is indeed very right. Allow me to explain. DNS, as the name obviously suggests, provides name resolution services to map domain names to IP addresses. In the end, everything on the Internet or on any network is just an IP address.

Since your network is small, your domain name and associated IP address will not be preserved across the global routing tables persistently and will be dropped. So when a DNS name resolution query comes in for your domain, the client will first request a resolution from the local DNS cache and then with the DNS servers for your ISP. Chances are great that it wont be available with them too, unless someone else has recently accessed your domain or if its very popular on the Internet or if its very large. Their servers either take it upon themselves to resolve the address and send the results back to the client trying to access your domain, or it will just send the address of its DNS server to the client. The process will keep going on and on until one of the servers sends a request to one of the 13 root DNS servers for an "authoritative" resolution, in which time your client's computer would have probably timed out waiting for the reply.

Its literally impossible for a request to be sent all the way to the root DNS servers, since some servers will maintain a persistent cache and they will send across a non-authoritative reply back to the client. But if you remember the IP address, you do not have this overhead associated with resolving a name to an IP address. So yes, you are right. At least your signature is.

The time required is negligible, but there is a DEFINITE overhead associated with DNS and name resolutions. So while the page may or may not load "faster" you are literally skipping the DNS overhead by memorizing an IP address.