ppp IP address problem

I have noticed a weird problem with pppd, when dialing from my notebook
compter. Often, instead of getting a proper IP from the ISP, the ppp0
connection will get the address of 192.168.1.30, which is the address it
eth0 when connected to my local network. This occurs even when eth0 is
disconnected from the lan. My dial up script also turns off eth0, before
dialing. I'm using kppp as the front end for pppd. Any ideas what might
be causing this problem?

tnx jk

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On Sun, 10 Aug 2003 14:16:49 GMT, James Knott <(E-Mail Removed)> wrote:
>
>
> I have noticed a weird problem with pppd, when dialing from my notebook
> compter. Often, instead of getting a proper IP from the ISP, the ppp0
> connection will get the address of 192.168.1.30, which is the address it
> eth0 when connected to my local network. This occurs even when eth0 is
> disconnected from the lan. My dial up script also turns off eth0, before
> dialing. I'm using kppp as the front end for pppd. Any ideas what might
> be causing this problem?
>
> tnx jk
>

Perhaps you need to re-configure the interface with route and ifconfig?


Alan


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James Knott <(E-Mail Removed)> writes:

]I have noticed a weird problem with pppd, when dialing from my notebook
]compter. Often, instead of getting a proper IP from the ISP, the ppp0
]connection will get the address of 192.168.1.30, which is the address it

Put nodefaultip
into /etc/ppp/options


]eth0 when connected to my local network. This occurs even when eth0 is
]disconnected from the lan. My dial up script also turns off eth0, before
]dialing. I'm using kppp as the front end for pppd. Any ideas what might

I doubt that very much. It may be that you have been relying on having a
default route to your eth0 to route traffic to the other machine on that
local net-- don't, use specific routing-- and you asked kppp to reassign
the default route.
Try running ifconfig -a after the ppp connection to see if eth0 is still
up. Then look at
route -n.

]be causing this problem?

]tnx jk

]--

]Fundamentalism is fundamentally wrong.

]To reply to this message, replace everything to the left of "@" with
]james.knott.

James Knott <(E-Mail Removed)> wrote:
> I have noticed a weird problem with pppd, when dialing from my notebook
> compter. Often, instead of getting a proper IP from the ISP, the ppp0
> connection will get the address of 192.168.1.30, which is the address it
> eth0 when connected to my local network. This occurs even when eth0 is
> disconnected from the lan. My dial up script also turns off eth0, before
> dialing. I'm using kppp as the front end for pppd. Any ideas what might
> be causing this problem?

I don't know what "turns off eth0" means but you might try adding the
pppd option noipdefault to /etc/ppp/options. It's supposed to prevent
pppd from offering a local interface IP address as it's address for the
PPP connection. That should force the ISP to supply a local IP address
for your PPP interface.

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PPP-Q&A links, downloads: http://ckite.no-ip.net/
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Alan Connor wrote:

> On Sun, 10 Aug 2003 14:16:49 GMT, James Knott <(E-Mail Removed)>
> wrote:
>>
>>
>> I have noticed a weird problem with pppd, when dialing from my notebook
>> compter. Often, instead of getting a proper IP from the ISP, the ppp0
>> connection will get the address of 192.168.1.30, which is the address it
>> eth0 when connected to my local network. This occurs even when eth0 is
>> disconnected from the lan. My dial up script also turns off eth0, before
>> dialing. I'm using kppp as the front end for pppd. Any ideas what might
>> be causing this problem?
>>
>> tnx jk
>>
>
> Perhaps you need to re-configure the interface with route and ifconfig?

This doesn't happen all the time, so I don't know what I could do different.
I suspect the problem may be at the ISP end, but I want to be absolutely
certain first. Also, until I know the IP I'm supposed to have - it changes
with the line connected to - I can't use ifconfig to set it. I have even
tried the "ipcp-accept-local" option in ppp, to force my computer to use
what the ISP should be providing, but it didn't help. I suppose what I
need is some method to monitor what's actually being received from the ISP.
That's easy enough to do with an external modem, but I'm not sure how to do
it with an internal "Winmodem".

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James Knott <(E-Mail Removed)> wrote:

> This doesn't happen all the time, so I don't know what I could do different.
> I suspect the problem may be at the ISP end, but I want to be absolutely
> certain first. Also, until I know the IP I'm supposed to have - it changes
> with the line connected to - I can't use ifconfig to set it. I have even
> tried the "ipcp-accept-local" option in ppp, to force my computer to use
> what the ISP should be providing, but it didn't help. I suppose what I

It won't help if pppd requests an IP address based on a local interface's
IP address, AND the ISP host PPP implementation is configured poorly
enough to accept the requested IP address as your's for the PPP link.

> need is some method to monitor what's actually being received from the ISP.
> That's easy enough to do with an external modem, but I'm not sure how to do
> it with an internal "Winmodem".

I don't think the modem is a part of this problem. Add the pppd option
debug to /etc/ppp/options and follow the recipe below to see what's
being negotiated for the PPP link.


/* Recipe for a unified PPP debug log file: Add the line
" local2.*;*.=debug;*.=notice /var/log/ppp-debug.log "
to /etc/syslog.conf, and do " kill -HUP `pidof syslogd` "
so that syslogd rereads it. */

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PPP-Q&A links, downloads: http://ckite.no-ip.net/
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Clifford Kite wrote:

>> tried the "ipcp-accept-local" option in ppp, to force my computer to use
>> what the ISP should be providing, but it didn't help. I suppose what I
>
> It won't help if pppd requests an IP address based on a local interface's
> IP address, AND the ISP host PPP implementation is configured poorly
> enough to accept the requested IP address as your's for the PPP link.
>

That's why I tried that ipcp-accept-local, as it's supposed to override a
local setting and get the ip from the other end. However, it doesn't make
any difference.

> > need is some method to monitor what's actually being received from the
ISP.
> > That's easy enough to do with an external modem, but I'm not sure how to
do
> > it with an internal "Winmodem".
>
> I don't think the modem is a part of this problem. Add the pppd option
> debug to /etc/ppp/options and follow the recipe below to see what's
> being negotiated for the PPP link.
>

I was referring to ease of monitoring an external modem, with another serial
port, so I an read all the data going by.

I'll have to try that log stuff, to see what happens.

tnx


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Clifford Kite wrote:

> I don't know what "turns off eth0" means but you might try adding the
> pppd option noipdefault to /etc/ppp/options. It's supposed to prevent
> pppd from offering a local interface IP address as it's address for the
> PPP connection. That should force the ISP to supply a local IP address
> for your PPP interface.
>

By "turns off eth0", I mean I run "ifconfig eth0 down", before starting the
dialer.

I'll have to try that noipdefault option, to see if it helps. As this is an
intermittent problem, that may take a while. The dial up works great for a
while, then this problem occurs for a while.

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James Knott <(E-Mail Removed)> wrote:
> Clifford Kite wrote:

>>> tried the "ipcp-accept-local" option in ppp, to force my computer to use
>>> what the ISP should be providing, but it didn't help. I suppose what I
>>
>> It won't help if pppd requests an IP address based on a local interface's
>> IP address, AND the ISP host PPP implementation is configured poorly
>> enough to accept the requested IP address as your's for the PPP link.
>>

> That's why I tried that ipcp-accept-local, as it's supposed to override a
> local setting and get the ip from the other end. However, it doesn't make
> any difference.

But that's the point. If pppd requests an IP address and the ISP
host is misconfigured and accepts it then the ISP doesn't suggest an
IP address of it's own choosing. The ISP SHOULD Nak the IP address
pppd requests and in doing so suggest one in it's own IP address pool.

Adding the noipdefault option causes pppd to request 0.0.0.0 for it's
IP address, which is a signal to the ISP that it must supply pppd's
IP address for the PPP link.

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PPP-Q&A links, downloads: http://ckite.no-ip.net/
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James Knott <(E-Mail Removed)> writes:

]Bill Unruh wrote:

]> James Knott <(E-Mail Removed)> writes:
]>
]> ]I have noticed a weird problem with pppd, when dialing from my notebook
]> ]compter. Often, instead of getting a proper IP from the ISP, the ppp0
]> ]connection will get the address of 192.168.1.30, which is the address it
]>
]> Put nodefaultip
]> into /etc/ppp/options

]That option is not listed in man pppd. Are you sure it's correct?

Sorry, noipdefault is the right option.

The default behaviour for pppd is to use an ethernet number as the
suggestion to the far side as to its own IP. The other side should
refuse it, and offer one of its own ip addresses. Apparently one of the
computers on the far side is misconfigured and instead accepts your
first request, resulting is a mess.
Alternatively you might have an IP in your /etc/ppp/options file or in
kppp.





]>
]>
]> ]eth0 when connected to my local network. This occurs even when eth0 is
]> ]disconnected from the lan. My dial up script also turns off eth0, before
]> ]dialing. I'm using kppp as the front end for pppd. Any ideas what might
]>
]> I doubt that very much. It may be that you have been relying on having a
]> default route to your eth0 to route traffic to the other machine on that
]> local net-- don't, use specific routing-- and you asked kppp to reassign
]> the default route.

]The route is fine. It's the assigned IP that's wrong. Also, the options
]file contains the defaultroute option, which adds the peer gateway to the
]routes.

It only does so if a default route does not already exist. I read your
post as pppd would stop your eth0 from working. If that is not the case,
then my suggestion is wrong.



]> Try running ifconfig -a after the ppp connection to see if eth0 is still
]> up. Then look at
]> route -n.

]I've run ifconfig many times and it always shows eth0 down. The routes are
]fine.

?? Why does it show eth0 down?