3g上網，IP變動問題 - Linux

我有一台ubuntu server的機器，透過華為的3g網卡上網
網卡資訊 http://www.pcstore.com.tw/sogynet/M10266362.htm

網卡直接接在主機的usb插槽上

但是連上網路之後卻發現，ppp0取得的ip

和我用curl ifconfig取得的ip不一致

現在ubuntu出的去，但是我卻無法ssh進去

不知道有經驗的板友都是怎麼連線的呢?

麻煩各位了~謝謝~

補充
eth0 Link encap:Ethernet HWaddr 08:00:27:63:68:cd
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1360 errors:0 dropped:0 overruns:0 frame:0
TX packets:868 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 KB)
Interrupt:17 Base address:0xc000

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:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

ppp0 Link encap:Point-to-Point Protocol
inet addr:42.72.90.213 P-t-P:10.64.64.64 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1
RX packets:9610 errors:0 dropped:0 overruns:0 frame:0
TX packets:11509 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:16479 (16.4 MB) TX bytes:14705 (14.7 KB)

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