can you help me in the concept of subnet mask calculation

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i implement the coding to get the subnet mask and the default gateway of the system..

following coding:

int main(int argc, char* argv[])
{
    PIP_ADAPTER_INFO pAdapterInfo;
    PIP_ADAPTER_INFO pAdapter=NULL;
    printf("Hello World!\n");
    DWORD dwRetVal=0;
    UINT i;
    WORD wVersionRequested;
    WSADATA wsaData;
    struct in_addr addr;
    int err;
    wVersionRequested = MAKEWORD(2, 2);
    err = WSAStartup(wVersionRequested, &wsaData);
    struct tm newtime;
    char buffer[32];
    ULONG ulOutBufLen=sizeof(PIP_ADAPTER_INFO);
    pAdapterInfo = (IP_ADAPTER_INFO *) malloc(sizeof (IP_ADAPTER_INFO));
    if (pAdapterInfo == NULL) {
        printf("Error allocating memory needed to call GetAdaptersinfo\n");
        return 1;
    }
    if(GetAdaptersInfo(pAdapterInfo, &ulOutBufLen)==ERROR_BUFFER_OVERFLOW)
    {
        free(pAdapterInfo);
        pAdapterInfo = (IP_ADAPTER_INFO *) malloc(ulOutBufLen);
        if (pAdapterInfo == NULL) {
            printf("Error allocating memory needed to call GetAdaptersinfo\n");
            return 1;
        }
    }
        if ((dwRetVal = GetAdaptersInfo(pAdapterInfo, &ulOutBufLen)) == NO_ERROR) {
        pAdapter = pAdapterInfo;
    pAdapter = pAdapterInfo;
    while(pAdapter)
    {
            printf("\tIP Mask: \t%s\n", pAdapter->IpAddressList.IpMask.String);
            printf("\tGateway: \t%s\n", pAdapter->GatewayList.IpAddress.String);
            Sleep(3000);
            pAdapter = pAdapter->Next;
    }
        }
        return 0;
}

problem is:

it return only one subnet mask and the default gateway of the system..
but my system having 3 subnet mask address..

i want to display these three ..
can you help me...

Posted 7-Jul-11 20:12pm

@BangIndia

Updated 8-Jul-11 3:36am

Albert Holguin

v4

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Comments

Prerak Patel 8-Jul-11 2:14am

Use pre tags for code section.

@BangIndia 9-Jul-11 1:58am

<pre lang="midl">IP_ADDR_STRING *p;
p=(pAdapter->IpAddressList.Next);
printf("final\t%s",p->IpMask.String);
p=p->Next;
printf("final\t%s",p->IpMask.String);
p=p->Next;</pre>

that is the soultion. myself i found.. its working good..

ThatsAlok 8-Jul-11 2:57am

could you debug this piece of code and check what pAdapter->next returning
while(pAdapter)
{
printf("\tIP Mask: \t%s\n", pAdapter->IpAddressList.IpMask.String);
printf("\tGateway: \t%s\n", pAdapter->GatewayList.IpAddress.String);
Sleep(3000);
pAdapter = pAdapter->Next;
}

@BangIndia 9-Jul-11 1:58am

<pre lang="midl">IP_ADDR_STRING *p;
p=(pAdapter->IpAddressList.Next);
printf("final\t%s",p->IpMask.String);
p=p->Next;
printf("final\t%s",p->IpMask.String);
p=p->Next;</pre>

that is the soultion. myself i found.. its working good..

3 solutions

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Timberbird · Answer 1 · 2011-07-07T20:52:00

Solution 1

MSDN contains a lot of info on your problem. This[^] article offers you to use GetAdaptersAddresses()[^] function on Windows XP and later, this[^] page tells you IpAddressList is actually a linked list (you can use Next member) and this[^] article describes function that can query loopback interface parameters, if needed

Posted 7-Jul-11 20:52pm

Timberbird

Comments

Sergey Alexandrovich Kryukov 8-Jul-11 3:22am

A 5. I know a good tutorial and a nice article on subnetting, please see my solution.
--SA

Timberbird 8-Jul-11 7:20am

Thank you. I had to perform task almost similar to OP's a several years ago; wish I read these articles back then :)

@BangIndia 8-Jul-11 8:43am

please can you help for that..
i read the article.. good..

Timberbird 8-Jul-11 9:34am

In your while(pAdapter) cycle, enumerate through pAdapter->IpAddressList and pAdapter->GatewayList using their Next member, just the same way you do it with pAdapter

@BangIndia 8-Jul-11 10:03am

sir where i want to store that element sir..
i can use the pAdapter->IpAddressList.Next .

but if i try to store
pAdapter->IpAddressList=pAdapter->IpAddressList.Next ;
it provide error sir.. what can i do now.. please sir help me

Timberbird 8-Jul-11 10:36am

But why are you trying to assign something to pAdapter->IpAddressList? Create a variable of type IP_ADDR_STRING, called for example pIpAddressList, and first set its value to pAdapter->IpAddressList. Then you only need to cycle through all values in the list by setting pIpAddressList = pIpAddressList->Next;

@BangIndia 9-Jul-11 1:58am

<pre lang="midl">IP_ADDR_STRING *p;
p=(pAdapter->IpAddressList.Next);
printf("final\t%s",p->IpMask.String);
p=p->Next;
printf("final\t%s",p->IpMask.String);
p=p->Next;</pre>

that is the soultion. myself i found.. its working good..

Timberbird 11-Jul-11 2:28am

This solution is not as good as it may seem. Actually, it's bad :). You skip one address when initializing p, you may skip more if your adapter has more than 3 address assigned, and this code will fail when adapter has less than 3 addresses. Try this one:

IP_ADDR_STRING *p;
p=(Adapter->IpAddressList);
while (p)
{
printf("final\t%s",p->IpMask.String);
p=p->Next;
}

Dhanasundhari 11-Jul-11 2:43am

no.. its not working...

producing error sir

Timberbird 11-Jul-11 3:04am

Ok, I must be wrong in that string: p=(Adapter->IpAddressList). Sorry for misguiding, try changing it to p=(pAdapter->IpAddressList.Next)

@BangIndia 11-Jul-11 8:12am

sir .. don't say sorry sir..
you are a big person..
that same coding only i use for my program...

Dhanasundhari 8-Jul-11 11:07am

ok sir,, i will try as you said

Sergey Alexandrovich Kryukov · Answer 2 · 2011-07-07T21:21:00

Solution 2

You can find pretty good detailed tutorial and a short and clear article on subnetting and the subnet masks here:

IP Address Subnetting Tutorial:
http://www.ralphb.net/IPSubnet/[^];

IP subnetting made easy:
http://www.techrepublic.com/article/ip-subnetting-made-easy/6089187[^].

—SA

Posted 7-Jul-11 21:21pm

Sergey Alexandrovich Kryukov

@BangIndia · Answer 3 · 2011-07-08T19:58:00

MIDL

IP_ADDR_STRING *p;
                  p=(pAdapter->IpAddressList.Next);
                  printf("final\t%s",p->IpMask.String);
                    p=p->Next;
                    printf("final\t%s",p->IpMask.String);
                    p=p->Next;

that is the soultion. myself i found.. its working good..

can you help me in the concept of subnet mask calculation

3 solutions

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