Why sending packets to broadcast IP?

I noticed a whole lot of traffic going on one of our subnets, and
brought up the IPCop (IDS/firewall/router PC) log summary, and found
this section:

Logged 832 packets on interface eth1
From 192.168.2.2 - 392 packets
To 192.168.2.1 - 219 packets
Service: domain (udp/53) (INPUT,eth1,none) - 219 packets
To 192.168.2.7 - 170 packets
Service: netbios-dgm (udp/138) (INPUT,eth1,none) - 170
packets
--snip--
From 192.168.2.3 - 440 packets
To 192.168.0.9 - 10 packets
Service: axon-lm (tcp/1548) (NEW not SYN?,eth1,eth0) - 10
packets
To 192.168.2.1 - 117 packets
Service: domain (udp/53) (INPUT,eth1,none) - 117 packets
To 192.168.2.7 - 313 packets
Service: netbios-ns (udp/137) (INPUT,eth1,none) - 84 packets
Service: netbios-dgm (udp/138) (INPUT,eth1,none) - 229
packets

192.168.2.2 is our file server
192.168.2.3 is our internal Web server
192.168.2.1 is the IPCop machine's NIC
192.168.2.7 is the broadcast IP for the subnet

Why in the world are the two servers sending so much traffic to the
broadcast IP?! I'm not terribly edumacated in TCP/IP networking I'm
afraid, so I guess this may be normal.
But it seems odd.
Thanks for any feedback!
-Liam

In comp.os.linux.networking, news@celticbear.com wrote:

> I noticed a whole lot of traffic going on one of our subnets, and
> brought up the IPCop (IDS/firewall/router PC) log summary, and found
> this section:
>
> Logged 832 packets on interface eth1
> From 192.168.2.2 - 392 packets
> To 192.168.2.1 - 219 packets
> Service: domain (udp/53) (INPUT,eth1,none) - 219 packets
> To 192.168.2.7 - 170 packets
> Service: netbios-dgm (udp/138) (INPUT,eth1,none) - 170
> packets
> --snip--
> From 192.168.2.3 - 440 packets
> To 192.168.0.9 - 10 packets
> Service: axon-lm (tcp/1548) (NEW not SYN?,eth1,eth0) - 10
> packets
> To 192.168.2.1 - 117 packets
> Service: domain (udp/53) (INPUT,eth1,none) - 117 packets
> To 192.168.2.7 - 313 packets
> Service: netbios-ns (udp/137) (INPUT,eth1,none) - 84 packets
> Service: netbios-dgm (udp/138) (INPUT,eth1,none) - 229
> packets
>
> 192.168.2.2 is our file server
> 192.168.2.3 is our internal Web server
> 192.168.2.1 is the IPCop machine's NIC
> 192.168.2.7 is the broadcast IP for the subnet
>
> Why in the world are the two servers sending so much traffic to the
> broadcast IP?!

Given the target ports of those packets, my guess is that you have SMB
servers running on 192.168.2.2 and 192.168.2.3, and they are performing the
requisite scan of your network for SMB client machines and SMB domain
controllers. netbios-ns is the SMB "Name server" port that lets client SMB
systems determine SMB network names, while netbios-dgm is the SMB datagram
port.



--
Lew Pitcher

Master Codewright & JOAT-in-training | Registered Linux User #112576
http://pitcher.digitalfreehold.ca/ | GPG public key available by request
---------- Slackware - Because I know what I'm doing. ------

On Jun 26, 11:14*am, Lew Pitcher <lpitc...@teksavvy.com> wrote:
> In comp.os.linux.networking, n...@celticbear.com wrote:
> > I noticed a whole lot of traffic going on one of our subnets, and
> > brought up the IPCop (IDS/firewall/router PC) log summary, and found
> > this section:
>
> > *Logged 832 packets on interface eth1
> > * * From 192.168.2.2 - 392 packets
> > * * * *To 192.168.2.1 - 219 packets
> > * * * * * Service: domain (udp/53) (INPUT,eth1,none) - 219 packets
> > * * * *To 192.168.2.7 - 170 packets
> > * * * * * Service: netbios-dgm (udp/138) (INPUT,eth1,none) - 170
> > packets
> > --snip--
> > * * From 192.168.2.3 - 440 packets
> > * * * *To 192.168.0.9 - 10 packets
> > * * * * * Service: axon-lm (tcp/1548) (NEW not SYN?,eth1,eth0) - 10
> > packets
> > * * * *To 192.168.2.1 - 117 packets
> > * * * * * Service: domain (udp/53) (INPUT,eth1,none) - 117 packets
> > * * * *To 192.168.2.7 - 313 packets
> > * * * * * Service: netbios-ns (udp/137) (INPUT,eth1,none) - 84 packets
> > * * * * * Service: netbios-dgm (udp/138) (INPUT,eth1,none) - 229
> > packets
>
> > 192.168.2.2 is our file server
> > 192.168.2.3 is our internal Web server
> > 192.168.2.1 is the IPCop machine's NIC
> > 192.168.2.7 is the broadcast IP for the subnet
>
> > Why in the world are the two servers sending so much traffic to the
> > broadcast IP?!
>
> Given the target ports of those packets, my guess is that you have SMB
> servers running on 192.168.2.2 and 192.168.2.3, and they are performing the
> requisite scan of your network for SMB client machines and SMB domain
> controllers. netbios-ns is the SMB "Name server" port that lets client SMB
> systems determine SMB network names, while netbios-dgm is the SMB datagram
> port.
>

Ah, that makes sense.
Just the number of packets surprised me.
Thanks for the info!