Internet Bandwidth and Broadcasting on LAN

[Amit Dixit_2]

Hi,
I am having a 512kbps bandwidth of internet
connection using DSL technology, in 1:3
ration shared medium.

But the problem is I dont get proper
bandwidth the service provider says that my
LAN is having to much of broadcasting.

Is there any tool thorugh which I can check ?
the braodcasting.

My LAN Includes Winx 9X clients, Windows NT
server and a Linux mail server

Few of the clients are having static IP and
few of them are obtaining Ip through DHCP.

How should I check broadcasting.
Apart from this after few hours the DSL
router doesnt pings the next hop as well
and my internet goes down entirely.

Thanks,
Amit.

[Jerome Henry]

Why not try to analyse frames using a tcpdump or ethereal, filtering only broadcast packets ? You'll see how numerous they are...

hth

J

[Amit Dixit_2]

how to configure ethereal or tcpdump for the same and how come I will know abt it through the output of the above softwares.

thanks,
amit

[Jerome Henry]

Could you describe slightly more your network configuration so I could suggest where to get this capture done (how many machines, connected thru switch or hub, router's position).

Tks.

J

[Amit Dixit_2]

Hi,
Thanks allot.

I am having 1 Cisco, 1 Dlink and 4 3Com
Switches. All are cascaded to cisco.

All users are connected to the Dlink or
3Com Switches.

The Cable DSL modem is terminated on Dlink.
Since it does'nt negotiate with CISCO.

The WINNT Server's and Linux Server Plus
HP Network Printer is also connected to
Cisco Switch + 2 Users.

All clients are running Windows 95/98 and
only TCP/IP is the protocol we are using.

Thanks,
Amit

[Jerome Henry]

Hi,

So I woudl start by installing ethereal on any D link connected windows client.
You'll get it here :
http://www.ethereal.com/download.html
You'll need to install before winpcap, which you'll find under windows installer section.
Launch a capture and filter by destination address... you'll see all broadcasts, and which machines they come from...

Tell if you have trouble with ethereal...

hth

J

[Olaf Borowski]

Amit,

If you have a decent switch, the internal counters of that switch will give you information about broadcast packets on each port (the Cisco box will do definetely do that). Use the CLI or a MIB browser to get access to those values. Looking at those values, try to figure out how many broadcast packets you see per second or over a certain period of time. This will give you a good indication of what is going on.

Olaf

[Stuart Teo]

Hi Amit,

Just a quick question. Why should local broadcasts matter? They don't get routed across the DSL router anyway and should have nothing to do with the sluggishness you're facing.

"This side" of the DSL router and "That side" are 2 seperate broadcast domains. Aren't they?

[Jerome Henry]

100% agree with Hwee Liang Teo... that's why I'm suggesting this ethereal : I am wondering what kind of broadcast can be routed and slow Internet connection, and even preventing you from getting next hop...
I had this kind of trouble twice, the first time, it was in fact some NetBios calls under b nodes that were filling router stack up, but the other time, it was my ISP not respecting its promisses...
Checking at frame level should get us know...

[Amit Dixit_2]

Hi,
I am sending an screeshot of ethereal.
Please have look at it andd tell me is my
network suffering from too much
broadcasting.

The machine 192.168.1.5 in the screen shot
is my linux server running sendmail using
LDAP.

And all the clients are running netscape.

Please see the attachment and give me your
valueable suggesgtions for the same.

Thanks,
Amit.