arm下GPRS拨号，能拨号上去，却不能通信。

PPP link to ppp0 terminated.
[root@FriendlyARM ppp]# ./ppp-on
Serial connection established.
using channel 4
Using interface ppp0
Connect: ppp0 <--> /dev/ttyS2
Warning - secret file /etc/ppp/pap-secrets has world and/or group access
sent [LCP ConfReq id=0x1 <asyncmap 0x20a0000> <magic 0x8fe3e752> <pcomp> <accomp
>]
rcvd [LCP ConfAck id=0x1 <asyncmap 0x20a0000> <magic 0x8fe3e752> <pcomp> <accomp
>]
rcvd [LCP ConfReq id=0xb <mru 1600> <auth pap> <magic 0xc3c65c9> <asyncmap 0x0>
<pcomp> <accomp>]
sent [LCP ConfRej id=0xb <auth pap>]
rcvd [LCP ConfReq id=0xc <mru 1600> <magic 0xc3c65c9> <asyncmap 0x0> <pcomp> <ac
comp>]
sent [LCP ConfAck id=0xc <mru 1600> <magic 0xc3c65c9> <asyncmap 0x0> <pcomp> <ac
comp>]
sent [IPCP ConfReq id=0x1 <addr 0.0.0.0> <compress VJ 0f 01>]
sent [CCP ConfReq id=0x1 <deflate 15> <deflate(old#) 15> <bsd v1 15>]
rcvd [LCP ProtRej id=0x3 80 fd 01 01 00 0f 1a 04 78 00 18 04 78 00 15 03 2f 32]
sent [IPCP ConfReq id=0x1 <addr 0.0.0.0> <compress VJ 0f 01>]
rcvd [IPCP ConfRej id=0x1 <compress VJ 0f 01>]
sent [IPCP ConfReq id=0x2 <addr 0.0.0.0>]
rcvd [IPCP ConfReq id=0x4 <addr 10.0.0.1>]
sent [IPCP ConfAck id=0x4 <addr 10.0.0.1>]
rcvd [IPCP ConfNak id=0x2 <addr 10.145.91.91>]
sent [IPCP ConfReq id=0x3 <addr 10.145.91.91>]
rcvd [IPCP ConfAck id=0x3 <addr 10.145.91.91>]
local IP address 10.145.91.91
remote IP address 10.0.0.1

ppp0 Link encap:Point-to-Point Protocol
inet addr:10.124.91.12 P-t-P:10.0.0.1 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1600 Metric:1
RX packets:4 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:40 (40.0 B) TX bytes:77 (77.0 B)

上面是PPP拨号的调试信息，及拨号完的PPP0的信息，虽然得到了IP就是PING不能其它的10.0.0.1，外网的IP地址也PING不通，也不能用SOCKET进行通信。我用的是SIM508，平台是友善之臂的MINI2410，拨号用的是PPP-2.4.1。请问这是为什么。