dirtytoyota@hotmail.com (PullnOutHair) writes:

]I am running PPP on a linux redhat 7.2 kernel to demand dial to some
]PC's out in the field. Occasionally my modem starts dialing and
]connects to a PC without any traffic being started for that IP. Is

No, you mean without you starting traffic. There almost certainly is
some traffic that is triggering the modem. Also it would help if you
told us your setup. Demand dialing is not to "some PCs' It is to a very
specific one. And it does this whenever ANY traffic needs to be sent to
whatever IP address.

]there something that would cause it to dial out and connect. The link
]seems to connect as if some broadcast traffic is starting the link.

Could be.

]Demand dialing is setup to disconnect with the idle command and the
]modem ends up connecting and then going dormant and disconnecting.
]This is happening several times throught a normal day. This concerns
]me about the PPP stability.

ppp stability is fine.

unruh@string.physics.ubc.ca (Bill Unruh) wrote in message news:...
> dirtytoyota@hotmail.com (PullnOutHair) writes:
>
> ]I am running PPP on a linux redhat 7.2 kernel to demand dial to some
> ]PC's out in the field. Occasionally my modem starts dialing and
> ]connects to a PC without any traffic being started for that IP. Is
>
> No, you mean without you starting traffic. There almost certainly is
> some traffic that is triggering the modem. Also it would help if you
> told us your setup. Demand dialing is not to "some PCs' It is to a very
> specific one. And it does this whenever ANY traffic needs to be sent to
> whatever IP address.

Actually, I am using ppp demand dialing to connect to 4 different PC's
right now. I have a function that replaces the call number dependent
upon which PC the traffic is for. Because of this I am not sure, nor
do the ppp debug logs show, which PC the traffic is for. I would love
it if I could set up demand dialing so that I could get rid of the
function and use strictly IP address to determine which number to
call. Currently, I have had to build that in and let all 4 PC's use
the same IP.

My setup is very basic since I am just starting out. I have PPP
configured for dial on demand, and also for dial-in as a server using
mgetty. I have the linux box acting as a server/firewall that uses
NAT to hide the subnet of the PPP machines that connect to it. My LAN
has a subnet of 10.0.0.x and the PPP is setup to have a subnet of
192.168.0.x. There shouldn't be any traffic that is generated outside
of the PPP network that can trigger a dial since the subnets won't
match up. The only machines on the PPP end are my linux box (PPP
server and demand dialer) and the PC that is on the other end that it
connects to. The problem is that all the machines that it connects to
use cellular modems and this random dialing eats up 2 minutes of
airtime everytime it happens because of the idle setting. I can't
lower this setting due to other program constraints. Anything that
you think would be helpful let me know. I am very glad to post
anything that may help you help me.

Thank you for all the past and future help.



>
> ]there something that would cause it to dial out and connect. The link
> ]seems to connect as if some broadcast traffic is starting the link.
>
> Could be.
>
> ]Demand dialing is setup to disconnect with the idle command and the
> ]modem ends up connecting and then going dormant and disconnecting.
> ]This is happening several times throught a normal day. This concerns
> ]me about the PPP stability.
>
> ppp stability is fine.

dirtytoyota@hotmail.com (PullnOutHair) writes:

]unruh@string.physics.ubc.ca (Bill Unruh) wrote in message news:...
]> dirtytoyota@hotmail.com (PullnOutHair) writes:
]>
]> ]I am running PPP on a linux redhat 7.2 kernel to demand dial to some
]> ]PC's out in the field. Occasionally my modem starts dialing and
]> ]connects to a PC without any traffic being started for that IP. Is
]>
]> No, you mean without you starting traffic. There almost certainly is
]> some traffic that is triggering the modem. Also it would help if you
]> told us your setup. Demand dialing is not to "some PCs' It is to a very
]> specific one. And it does this whenever ANY traffic needs to be sent to
]> whatever IP address.

]Actually, I am using ppp demand dialing to connect to 4 different PC's
]right now. I have a function that replaces the call number dependent
]upon which PC the traffic is for. Because of this I am not sure, nor

OK, you have a non-standard useage of ppp demand dialing. Not surprising
that you might have some issues.
Note that they might be some sort of broadcast packets, or arp requests
that are getting sent out. Can you use tcpdump to see what the traffic
is? (Not sure if there is any device to attack tcpdump to when it is
down under demand dialing however).


]do the ppp debug logs show, which PC the traffic is for. I would love
]it if I could set up demand dialing so that I could get rid of the
]function and use strictly IP address to determine which number to
]call. Currently, I have had to build that in and let all 4 PC's use
]the same IP.

The packet is almost certainly for the IP address, not for some specific
PC.



]My setup is very basic since I am just starting out. I have PPP
]configured for dial on demand, and also for dial-in as a server using
]mgetty. I have the linux box acting as a server/firewall that uses
]NAT to hide the subnet of the PPP machines that connect to it. My LAN
]has a subnet of 10.0.0.x and the PPP is setup to have a subnet of
]192.168.0.x. There shouldn't be any traffic that is generated outside
]of the PPP network that can trigger a dial since the subnets won't
]match up. The only machines on the PPP end are my linux box (PPP

A broadcast packet matches everything.


]server and demand dialer) and the PC that is on the other end that it
]connects to. The problem is that all the machines that it connects to
]use cellular modems and this random dialing eats up 2 minutes of
]airtime everytime it happens because of the idle setting. I can't
]lower this setting due to other program constraints. Anything that
]you think would be helpful let me know. I am very glad to post
]anything that may help you help me.

I am not sure I can be of further help, since I do not know demand
dialing well at all.

You might want to look into diald, the old program for doing demand
dialing. I think it had a packet filter option which could be used to
restrict the types of packets which would trigger the dialout.
But you still need to find out what is triggering it. Are there regular
times that this is happening?



]Thank you for all the past and future help.
]


]>
]> ]there something that would cause it to dial out and connect. The link
]> ]seems to connect as if some broadcast traffic is starting the link.
]>
]> Could be.
]>
]> ]Demand dialing is setup to disconnect with the idle command and the
]> ]modem ends up connecting and then going dormant and disconnecting.
]> ]This is happening several times throught a normal day. This concerns
]> ]me about the PPP stability.
]>
]> ppp stability is fine.

dirtytoyota@hotmail.com (PullnOutHair) writes:
> I am running PPP on a linux redhat 7.2 kernel to demand dial to some
> PC's out in the field. Occasionally my modem starts dialing and
> connects to a PC without any traffic being started for that IP.

That doesn't sound likely.

However, assuming you've got a recent version of pppd (you didn't
say), a reasonable thing to do would be to look at the debug logs --
the first packet sent after bringing the link up should be the
culprit. If that's not doable for some reason, then instrumenting
ip_active_pkt() in ipcp.c should reveal what's triggering the dial
(assuming it's IPv4 activity).

> Is
> there something that would cause it to dial out and connect. The link
> seems to connect as if some broadcast traffic is starting the link.

Broadcast traffic is not forwarded by the Linux kernel, at least by
default. Even if it were forwarded, this wouldn't be a problem in PPP
itself -- it'd just be doing what was asked. The real problem (if
there were such a problem) would be in the kernel itself.

> Demand dialing is setup to disconnect with the idle command and the
> modem ends up connecting and then going dormant and disconnecting.
> This is happening several times throught a normal day. This concerns
> me about the PPP stability.

It shouldn't.

--
James Carlson, IP Systems Group
Sun Microsystems / 1 Network Drive 71.234W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.497N Fax +1 781 442 1677