Broadcast Side Effect

What may be the side effect of using a wrong broadcast address?
My IP address is 198.44.182.175
My Netmask is 255.255.255.224
That's all that was given my the ISP plus the nameservers

I tried calculationg the broadcast and network address myself
I came up wit
Broadcast: 198.44.182.162 (is it suppose to be 162 or 161? i.e. the
last octet)
then the network address: 198.44.182.160

I've done the other required stuffs (etc/hosts, ip_forward = 1,modified
the apt network scripts /etc/sysconfig/network-scripts et al)

My route table looks fine............ in fact I can ping the ISP server
gateway,nameserver (can tis be possible if my broadcast address is not
correct?)
I have a workin NAT script: (IP Masquerading HOWTO samples)

I can't browse from a (microsoft) LAN system. I have four systems
running on the network, three runnin XP while the last one runs Win
Server 2003. However, its only one of the LAN (one of the XP systems)
that can ping the linux server also acting as gateway to internet
(Fedora Core 3) even though I have them (LAN systems) in the /etc/hosts
file with their hostnames.

Can a wrong broadcast address cause this?

Can anybody also give a chat (live) channel where one can ask
questions? I know of MiRC but I need more or may be I need to know more
servers/channels. Besides, they seem not to have time for people's
problems.

On 9 Jun 2005 06:38:56 -0700, (E-Mail Removed)
<(E-Mail Removed)> wrote:

> My IP address is 198.44.182.175
> My Netmask is 255.255.255.224

Netmask is bitwise-anded with a the IP to give the network address. The
first three octets are all ones, so that's easy. The last octet works
like this:

224 decimal = 1110 0000 binary (mask)
175 decimal = 1010 1111 binary (addr)

This gives a network of 1010 0000 = 160 decimal. Addresses on that
network can have a last five bits of 0 0000 through 1 1111 or zero
through 31 decimal. The last address is reserved for broadcast. So the
broadcast is 160 + 31 = 191.


> Broadcast: 198.44.182.162 (is it suppose to be 162 or 161? i.e. the
> last octet)

Should be 191.


> then the network address: 198.44.182.160

That's correct.


> I can't browse from a (microsoft) LAN system. [...] Can a wrong
> broadcast address cause this?

Yes. Which isn't to say that's the only thing that can break MS
browsing...


--
-| Bob Hauck
-| A proud member of the reality-based community.
-| http://www.haucks.org/

On 9 Jun 2005 06:38:56 -0700, "(E-Mail Removed)"
<(E-Mail Removed)> wrote:

>What may be the side effect of using a wrong broadcast address?
>My IP address is 198.44.182.175
>My Netmask is 255.255.255.224
>That's all that was given my the ISP plus the nameservers
>
>I tried calculationg the broadcast and network address myself
>I came up wit
>Broadcast: 198.44.182.162 (is it suppose to be 162 or 161? i.e. the
>last octet)
>then the network address: 198.44.182.160

I'm not going to deal with the internet access issues, but - according
to the netmask you gave - your network has 32 IPs ranging from .160
through .191. Therefore your broadcast address is 198.44.182.191

If you have ipmask, 'ipmask 255.255.255.224 198.44.182.175'. The
first reply is the broadcast address and the second is the network
address.

Your ISP _must_ have also provided a Gateway IP. This would normally
be either .161 or .190 (in a sane environment).

You can also get the network address from iptables by
iptables -I INPUT -d 198.44.192.175/27 -j LOG
iptables -nvL | less
iptables -D INPUT -d 198.44.192.175/27 -j LOG

and you can convert from a netmask to CIDR by counting
Number of IPS: 1 2 4 8 16 32
MASK: 255 254 252 248 224
CIDR: 32 31 30 29 28 27

There are also calculators on the web where you provide what you know
and get a reply (from the good ones of) the unknowns.

HTH,
buck

In the Usenet newsgroup comp.os.linux.networking, in article
<(E-Mail Removed) .com>,
(E-Mail Removed) wrote:

>What may be the side effect of using a wrong broadcast address?

Depends on the O/S involved and the type of datalink, but it can preclude
networking.

>My IP address is 198.44.182.175

Interesting - none of the Regional Internet Registries has allocate anything
in 198.44.x.x to anyone. You may want to recheck with the ISP.

>My Netmask is 255.255.255.224
>That's all that was given my the ISP plus the nameservers

[compton ~]$ whatis ipcalc
ipcalc (1) - perform simple manipulation of IP addresses
[compton ~]$

IP 198.33.182.175 1100 0110 0010 0001 1011 0110 1010 1111
mask 255.255.255.224 1111 1111 1111 1111 1111 1111 1110 0000
^ ^^^^
Net 198.33.182.160 1100 0110 0010 0001 1011 0110 1010 0000
B'cast 198.33.182.191 1100 0110 0010 0001 1011 0110 1011 1111

See RFC1878.

>I tried calculationg the broadcast and network address myself
>I came up wit
>Broadcast: 198.44.182.162 (is it suppose to be 162 or 161? i.e. the
>last octet)
>then the network address: 198.44.182.160

Assuming you are using a fixed width font, notice the carets below
the zeros in the netmask above. That's the span of your address
range - so the lowest address is where all of those are zero, which
is 198.33.182.160 - that's also the "network address". The highest
address would be where those last five bits are 'one' or 198.33.182.191.
That's your broadcast and is unusable for for anything else. The normal
interpretation is that you would have hosts from 198.33.182.161 to
198.33.182.190, though one of those is going to be your gateway to the
ISP (and the world).

>I can't browse from a (microsoft) LAN system. I have four systems
>running on the network, three runnin XP while the last one runs Win
>Server 2003. However, its only one of the LAN (one of the XP systems)
>that can ping the linux server also acting as gateway to internet
>(Fedora Core 3) even though I have them (LAN systems) in the /etc/hosts
>file with their hostnames.

"ipconfig /all"

"route print"

Both commands will display a pile of crap, because windoze doesn't want
users looking at technical stuff, and tries to intimidate people. Make
sure you windoze boxes are using addresses within your range noted above,
and that it has the correct netmask.

>Can a wrong broadcast address cause this?

Yes, but both Linux and windoze should barf on incorrectly calculated
addresses. What does 'tcpdump' show?

>Can anybody also give a chat (live) channel where one can ask questions?

Sorry, this is Usenet, not a chat room.

>I know of MiRC but I need more or may be I need to know more
>servers/channels.

http://ibiblio.org/pub/linux/docs/HOWTO/
http://en.tldp.org/HOWTO/HOWTO-INDEX/howtos.html

http://ibiblio.org/pub/linux/docs/linux-doc-project/
http://tldp.org/guides.html

>Besides, they seem not to have time for people's problems.

Remember, we are not being paid. If you want to pay for assistance, the
last two URLs above will get you to the Linux Documentation Project. There,
you will find the 'linux-consultants-guide' which lists hundreds of people
who can help for a fee. You will also find the 'nag2' which is the second
edition of the network-guide (Linux Network Administrator's Guide).

Old guy