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Re: [debian-knoppix] Can connect to ISP but can't connect to Internet (Former re: Modem problem)



Hi Stephen,

On Fri, Aug 01, 2003 at 19:15:00 +0800, Stephen Liu wrote:

> root@ttyp0[root]# ifconfig ppp0
> ppp0  Link encap:Point-to-Point Protocol
>       inet addr:202.123.68.1  P-t-P:202.123.71.254 Mask:255.255.255.255
>       UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1492  Metric:1
>       RX packets:4 errors:0 dropped:0 overruns:0 frame:0
>       TX packets:5 errors:0 dropped:0 overruns:0 carrier:0
>       collisions:0 txqueuelen:3
>       RX bytes:64 (64.0 b)  TX bytes:97 (97.0 b)
> 
> root@ttyp2[root]# ping 202.123.68.1
> PING 202.123.68.1 (202.123.68.1): 56 data bytes
> 64 bytes from 202.123.68.1: icmp_seq=0 ttl=64 time=0.2 ms

You pinging your _local_ IP address of the ppp0 interface. For this, no
packets must be sent over the dsl connection. For a real test, ping the
IP address of the peer (202.123.71.254 in the example above).


If you want to know over which interface/gateway an IP packet will be
sent, try
$ ip route get <ip-address>

For the example above, you should get:

$ ip route get 202.123.68.1
local 202.123.68.1 dev lo  src 202.123.68.1
    cache <local>  mtu 16436 advmss 16396

Packets to 202.123.68.1 will be sent over the local loopback (lo)
interface, because 202.123.68.1 is a local IP address.

The same command for the peer address:

$ ip route get 202.123.71.254
202.123.71.254 dev ppp0  src 202.123.68.1
    cache  mtu 1492 advmss 1452

Packets to 202.123.71.254 will be sent over the PPP interface (ppp0),
because it is the peer address of the PPP link. If the default route is
also set to use ppp0, any other non-local IP address will also use the
PPP link.

bye,
  Chris
-- 
Christian Perle                                   perle@itm.tu-clausthal.de
Grunaer Str. 31                      http://www.itm.tu-clausthal.de/~perle/
01069 Dresden                   LinuxGuitarKitesBicyclesBeerPizzaRaytracing
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