Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.os.linux.networking > #1270 > unrolled thread

default route ignored when ppp0 up

Back to article view | Back to comp.os.linux.networking

Contents

  default route ignored when ppp0 up Don <don.w.tucker@gmail.com> - 2012-04-10 07:35 -0700
    Re: default route ignored when ppp0 up J G Miller <miller@yoyo.ORG> - 2012-04-10 15:49 +0000
      Re: default route ignored when ppp0 up Andy Furniss <spam@andyfurniss.entadsl.com> - 2012-04-10 17:04 +0100
        Re: default route ignored when ppp0 up J G Miller <miller@yoyo.ORG> - 2012-04-10 16:12 +0000
      Re: default route ignored when ppp0 up Don <don.w.tucker@gmail.com> - 2012-04-10 10:10 -0700
    Re: default route ignored when ppp0 up Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2012-04-10 20:52 +0200
      Re: default route ignored when ppp0 up Don <don.w.tucker@gmail.com> - 2012-04-10 15:04 -0700
        Re: default route ignored when ppp0 up Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2012-04-11 00:52 +0200
          Re: default route ignored when ppp0 up Don <don.w.tucker@gmail.com> - 2012-04-11 07:25 -0700
            Re: default route ignored when ppp0 up Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2012-04-12 23:04 +0200
              Re: default route ignored when ppp0 up Don <don.w.tucker@gmail.com> - 2012-05-01 08:49 -0700

#1270 — default route ignored when ppp0 up

I have a Lenny Debian distro with a 2.6.21 kernel.  I start with a
single Ethernet interface to the Internet:

tcors01:~# netstat -rn
 Kernel IP routing table
 Destination     Gateway         Genmask  Flags MSS Window irtt Iface
 129.116.XXX.  0 0.0.0.0             255.255.255.0 U    0 0 0 eth2
 0.0.0.0             129.116.XXX.254           0.0.0.0 UG 0 0 0 eth2
 tcors01:~# ping 8.8.8.8
 PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
 64 bytes from 8.8.8.8: icmp_seq=1 ttl=48 time=35.0 ms
 64 bytes from 8.8.8.8: icmp_seq=2 ttl=48 time=30.3 ms

--- 8.8.8.8 ping statistics ---
 2 packets transmitted, 2 received, 0% packet loss, time 1006ms
 rtt min/avg/max/mdev = 30.381/32.726/35.072/2.352 ms

The default route works fine until I bring up a point-to-point
interface.

tcors01:~# pon att
 tcors01:~# netstat -rn
 Kernel IP routing table
 Destination       Gateway     Genmask    Flags MSS Window irtt Iface
 192.168.111.111    0.0.0.0 255.255.255.255 UH 0 0 0 ppp0
 129.116.XXX.0       0.0.0.0 255.255.255.0     U    0 0 0 eth2
 0.0.0.0   129.116.XXX.254             0.0.0.0     UG 0 0 0 eth2
 tcors01:~# ping 8.8.8.8
 PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
 From 129.116.XXX.27 icmp_seq=1 Destination Host Unreachable
 From 129.116.XXX.27 icmp_seq=2 Destination Host Unreachable
 From 129.116.XXX.27 icmp_seq=3 Destination Host Unreachable

--- 8.8.8.8 ping statistics ---
 5 packets transmitted, 0 received, +3 errors, 100% packet loss, time
4012ms
 , pipe 3

Why does the default route fail with the addition of the ppp0
interface to the routing table?

[toc] | [next] | [standalone]

#1272

On Tuesday, April 10th, 2012, at 07:35:48h -0700, Don wrote:

> Why does the default route fail with the addition of the ppp0
> interface to the routing table?

Probably because you are using the Debian scripts to bring up ppp0
which invokes a script to change the default route.  As I do not
have ppp installed I cannot say which one but you should look in
/etc/ppp at the scripts there for if-up* and also probably in
/etc/network/if-up.d for one related to ppp.

And yes you do have to fight with those scripts to stop the
default route from being changed.

[toc] | [prev] | [next] | [standalone]

#1273

J G Miller wrote:
> On Tuesday, April 10th, 2012, at 07:35:48h -0700, Don wrote:
>
>> Why does the default route fail with the addition of the ppp0
>> interface to the routing table?
>
> Probably because you are using the Debian scripts to bring up ppp0
> which invokes a script to change the default route.  As I do not
> have ppp installed I cannot say which one but you should look in
> /etc/ppp at the scripts there for if-up* and also probably in
> /etc/network/if-up.d for one related to ppp.

IIRC there's a pppd option defaultroute it may be in /etc/ppp/options.

This can be changed to nodefaultroute.

Of course distro scripts may also be involved eg passing defaultroute on 
the command line.

[toc] | [prev] | [next] | [standalone]

#1274

On Tuesday, April 10th, 2012, at 17:04:27h +0100, Andy Furniss wrote:

> IIRC there's a pppd option defaultroute it may be in /etc/ppp/options.
> 
> This can be changed to nodefaultroute.

Sounds right.

Seems that this option was added in 2010 long after I stopped using ppp.

<http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=578726>

Bizarrely somebody else had exactly the opposite problem.

<http://forums.debian.NET/viewtopic.php?f=5&t=76449>

Hopefully from the above, Don Tucker can get his ppp setup
to leave the default route alone.

[toc] | [prev] | [next] | [standalone]

#1275

On Apr 10, 10:49 am, J G Miller <mil...@yoyo.ORG> wrote:
> On Tuesday, April 10th, 2012, at 07:35:48h -0700, Don wrote:
> > Why does the default route fail with the addition of the ppp0
> > interface to the routing table?
>
> Probably because you are using the Debian scripts to bring up ppp0
> which invokes a script to change the default route.  As I do not
> have ppp installed I cannot say which one but you should look in
> /etc/ppp at the scripts there for if-up* and also probably in
> /etc/network/if-up.d for one related to ppp.
>
> And yes you do have to fight with those scripts to stop the
> default route from being changed.

Thank you for your reply, but I do not believe that is the issue.  I
am familiar with the nodefaultroute option in the /etc/ppp/peers/
provider file.  I am using it.  That is why the routing table has ppp0
added as a host route (as shown in the original post) after bringing
up ppp0, but it does NOT have ppp0 shown as a gateway route (i.e. with
the 'G' flag).  If I do not use the nodefaultroute option, after
bringing ppp0 up ppp0 DOES appear in the routing table with the 'G'
flag.

Don

[toc] | [prev] | [next] | [standalone]

#1277

Hello,

Don a écrit :
> I have a Lenny Debian distro with a 2.6.21 kernel.  I start with a
> single Ethernet interface to the Internet:
> 
> tcors01:~# netstat -rn
>  Kernel IP routing table
>  Destination     Gateway         Genmask  Flags MSS Window irtt Iface
>  129.116.XXX.  0 0.0.0.0             255.255.255.0 U    0 0 0 eth2
>  0.0.0.0             129.116.XXX.254           0.0.0.0 UG 0 0 0 eth2
>  tcors01:~# ping 8.8.8.8
>  PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
>  64 bytes from 8.8.8.8: icmp_seq=1 ttl=48 time=35.0 ms
>  64 bytes from 8.8.8.8: icmp_seq=2 ttl=48 time=30.3 ms
> 
> --- 8.8.8.8 ping statistics ---
>  2 packets transmitted, 2 received, 0% packet loss, time 1006ms
>  rtt min/avg/max/mdev = 30.381/32.726/35.072/2.352 ms
> 
> The default route works fine until I bring up a point-to-point
> interface.
> 
> tcors01:~# pon att
>  tcors01:~# netstat -rn
>  Kernel IP routing table
>  Destination       Gateway     Genmask    Flags MSS Window irtt Iface
>  192.168.111.111    0.0.0.0 255.255.255.255 UH 0 0 0 ppp0
>  129.116.XXX.0       0.0.0.0 255.255.255.0     U    0 0 0 eth2
>  0.0.0.0   129.116.XXX.254             0.0.0.0     UG 0 0 0 eth2
>  tcors01:~# ping 8.8.8.8
>  PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
>  From 129.116.XXX.27 icmp_seq=1 Destination Host Unreachable
>  From 129.116.XXX.27 icmp_seq=2 Destination Host Unreachable
>  From 129.116.XXX.27 icmp_seq=3 Destination Host Unreachable

This message normally means that the " next hop" (either router or final
destination) IP address could not be resolved with ARP.

> --- 8.8.8.8 ping statistics ---
>  5 packets transmitted, 0 received, +3 errors, 100% packet loss, time
> 4012ms
>  , pipe 3
> 
> Why does the default route fail with the addition of the ppp0
> interface to the routing table?

What is 129.116.XXX.27 ? The host itself, I guess ?
What is the output of : ip route get 8.8.8.8
What is the output of : ping 129.116.XXX.254
What is the output of : ip neigh
While trying to ping 8.8.8., what is the output of : tcpdump -ni eth2

[toc] | [prev] | [next] | [standalone]

#1278

On Apr 10, 1:52 pm, Pascal Hambourg <boite-a-s...@plouf.fr.eu.org>
wrote:
> Hello,
>
> Don a écrit :
Hello, and thank you for your interest.

> What is 129.116.XXX.27 ? The host itself, I guess ?
That is the static IP address of the eth2 interface.

> What is the output of : ip route get 8.8.8.8
tcors01:~# ip route get 8.8.8.8
8.8.8.8 via 129.116.XXX.254 dev eth2  src 129.116.XXX.27
    cache  mtu 1500 advmss 1460 hoplimit 64

> What is the output of : ping 129.116.XXX.254
tcors01:~# ping 129.116.XXX.254
PING 129.116.XXX.254 (129.116.XXX.254) 56(84) bytes of data.
From 129.116.XXX.27 icmp_seq=10 Destination Host Unreachable
From 129.116.XXX.27 icmp_seq=11 Destination Host Unreachable
From 129.116.XXX.27 icmp_seq=12 Destination Host Unreachable

--- 129.116.XXX.254 ping statistics ---
13 packets transmitted, 0 received, +3 errors, 100% packet loss, time
12001ms
, pipe 3

> What is the output of : ip neigh
tcors01:~# ip neigh
129.116.XXX.254 dev eth2  FAILED

> While trying to ping 8.8.8., what is the output of : tcpdump -ni eth2
tcors01:~# tcpdump -r eth2dump.log
reading from file eth2dump.log, link-type EN10MB (Ethernet)
22:01:43.987949 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
27, length 28
22:01:44.987696 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
27, length 28
22:01:45.987553 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
27, length 28
22:01:47.857363 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
27, length 28
22:01:48.857228 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
27, length 28
22:01:49.857100 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
27, length 28
22:01:51.856821 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
27, length 28
22:01:52.856628 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
27, length 28
22:01:53.856490 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
27, length 28

[toc] | [prev] | [next] | [standalone]

#1279

Don a écrit :
> 
>> While trying to ping 8.8.8., what is the output of : tcpdump -ni eth2
> tcors01:~# tcpdump -r eth2dump.log
> reading from file eth2dump.log, link-type EN10MB (Ethernet)
> 22:01:43.987949 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
> 27, length 28
> 22:01:44.987696 ARP, Request who-has 129.116.XXX.254 tell 129.116.XXX.
> 27, length 28
[...]
Routing is fine, but the gateway does not reply to ARP queries - or at
least your box does not receive them. This looks like a layer-2 issue. I
cannot see how the PPP connection could possibly cause this.
What kind of PPP connection is it ?

[toc] | [prev] | [next] | [standalone]

#1284

On Apr 10, 5:52 pm, Pascal Hambourg <boite-a-s...@plouf.fr.eu.org>
wrote:
> Routing is fine, but the gateway does not reply to ARP queries - or at
> least your box does not receive them. This looks like a layer-2 issue. I
> cannot see how the PPP connection could possibly cause this.
> What kind of PPP connection is it ?

It is a cellular modem connecting through AT&T as an ISP.

tcors01:~# ifconfig ppp0
 ppp0 Link encap:Point-to-Point Protocol
 inet addr:32.176.37.1 P-t-P:192.168.111.111 Mask:255.255.255.255
 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1

[toc] | [prev] | [next] | [standalone]

#1289

Don a écrit :
> On Apr 10, 5:52 pm, Pascal Hambourg <boite-a-s...@plouf.fr.eu.org>
> wrote:
>> Routing is fine, but the gateway does not reply to ARP queries - or at
>> least your box does not receive them. This looks like a layer-2 issue. I
>> cannot see how the PPP connection could possibly cause this.
>> What kind of PPP connection is it ?
> 
> It is a cellular modem connecting through AT&T as an ISP.

So it seems to be unrelated with the ethernet interface (unlike a PPPoE
connection). Again, I cannot see a reason for the behaviour you observe.

What happens if the gateway or another host on the ethernet network
tries to communicate with the Debian system ?
Is the communication on eth2 restored after the PPP connection is
terminated ?

[toc] | [prev] | [next] | [standalone]

#1346

On Apr 12, 4:04 pm, Pascal Hambourg <boite-a-s...@plouf.fr.eu.org>
wrote:
> Don a écrit :
>
> > On Apr 10, 5:52 pm, Pascal Hambourg <boite-a-s...@plouf.fr.eu.org>
> > wrote:
> >> Routing is fine, but the gateway does not reply to ARP queries - or at
> >> least your box does not receive them. This looks like a layer-2 issue. I
> >> cannot see how the PPP connection could possibly cause this.
> >> What kind of PPP connection is it ?
>
> > It is a cellular modem connecting through AT&T as an ISP.
>
> So it seems to be unrelated with the ethernet interface (unlike a PPPoE
> connection). Again, I cannot see a reason for the behaviour you observe.
>
> What happens if the gateway or another host on the ethernet network
> tries to communicate with the Debian system ?
> Is the communication on eth2 restored after the PPP connection is
> terminated ?

It turned out that this was a driver issue for that particular
Ethernet port.  The manufacturer of the PC/104 peripheral Ethernet
board did not support 2.6 kernel version drivers for that board.  2.4
kernel drivers seem to work fine, and the other Ethernet port on the
board works fine as well.  Thank you for your help!

Don

[toc] | [prev] | [standalone]

Back to top | Article view | comp.os.linux.networking

csiph-web