2811 wan口无法和对端设备1.1.1.2连接，
Serial0/0 current state :UP
Line protocol current state :DOWN
Description : Serial0/0 Interface
The Maximum Transmit Unit is 1500, Hold timer is 10(sec)
Internet Address is 1.1.1.1/30
Link layer protocol is PPP
LCP reqsent
Output queue : (Urgent queuing : Size/Length/Discards) 0/50/0
Output queue : (Protocol queuing : Size/Length/Discards) 0/500/0
Output queue : (FIFO queuing : Size/Length/Discards) 0/75/0
Physical layer is synchronous,Baudrate is 64000 bps
Interface is DCE, Cable type is V24
Last clearing of counters: Never
Last 300 seconds input rate 0.00 bytes/sec, 0 bits/sec, 0.00 packets/sec
Last 300 seconds output rate 2.09 bytes/sec, 16 bits/sec, 0.11 packets/sec
Input: 0 packets, 0 bytes
0 broadcasts, 0 multicasts
0 errors, 0 runts, 0 giants
0 CRC, 0 align errors, 0 overruns
0 dribbles, 0 aborts, 0 no buffers
0 frame errors
Output:58 packets, 1044 bytes
0 errors, 0 underruns, 0 collisions
0 deferred
DCD=UP DTR=UP DSR=UP RTS=DOWN CTS=UP
debug信息：
*0.475732 xxx PPP/8/debug2:
PPP Event:
Serial0/0 LCP TO+(Timeout with counter > 0) Event
state reqsent , Retransmit = 3
*0.475732 xxx PPP/8/debug2:
PPP Packet:
Serial0/0 Output LCP(c021) Pkt, Len 18
State reqsent, code ConfReq(01), id 25, len 14
MRU(1), len 4, val 05dc
MagicNumber(5), len 6, val 0007a848
*0.485732 xxx PPP/8/debug2:
PPP Event:
Serial0/0 LCP TO+(Timeout with counter > 0) Event
state reqsent , Retransmit = 2
*0.485732 xxx PPP/8/debug2:
PPP Packet:
Serial0/0 Output LCP(c021) Pkt, Len 18
State reqsent, code ConfReq(01), id 26, len 14
MRU(1), len 4, val 05dc
MagicNumber(5), len 6, val 0007abbb
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