I am using DSL(PPPOE) connection in ubuntu. It has two part (I am not sure), when I just connect the cable, system automatically get an IP address started with 172.x.x.x(DHCP). When I connect using username/password (PPPOE) I get another IP started with 10.x.x.x and can access internet but can't access some local IP (in my LAN), which are some FTP, media server provided by my ISP. I complained about that to my ISP but they reply

Windows is working

It's true, Windows 7 is working fine with this settings. I can access internet and local server at the same time. Also I use a WIFI router (TP-link TL-WR340G/TL-WR340GD) which result the same problem. So when I connect cable directly to system and use Windows 7 than everything is fine. Otherwise problem. Similar problem discussed here.

Edit

before connect.

route -n

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         172.100.0.1     0.0.0.0         UG    0      0        0 eth0
172.100.0.0     0.0.0.0         255.255.0.0     U     1      0        0 eth0

after connect.

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.12.44.91     0.0.0.0         UG    0      0        0 ppp0
10.12.44.91     0.0.0.0         255.255.255.255 UH    0      0        0 ppp0

ifconfig after connect

eth0      Link encap:Ethernet  HWaddr 74:d0:2b:d5:b3:6c  
          inet6 addr: fe80::76d0:2bff:fed5:b36c/64 Scope:Link
          inet6 addr: 2002:ac64:154:c:76d0:2bff:fed5:b36c/64 Scope:Global
          inet6 addr: fec0::c:76d0:2bff:fed5:b36c/64 Scope:Site
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:26582 errors:0 dropped:18 overruns:0 frame:0
          TX packets:2340 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2542063 (2.5 MB)  TX bytes:244938 (244.9 KB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:4118 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4118 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:336759 (336.7 KB)  TX bytes:336759 (336.7 KB)

ppp0      Link encap:Point-to-Point Protocol  
          inet addr:10.12.44.95  P-t-P:10.12.44.91  Mask:255.255.255.255
          inet6 addr: fe80::a536:c7ae:e079:d88d/10 Scope:Link
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1492  Metric:1
          RX packets:689 errors:0 dropped:0 overruns:0 frame:0
          TX packets:744 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3 
          RX bytes:385746 (385.7 KB)  TX bytes:75296 (75.2 KB)

I used network manager to create network(DSL connection)