msr3610 GRE Cisco2811

华三的msr3610和思科的2811做GRE VPN，两边无法通讯，GRE的配置很简单就不贴了；

在2811路由上ping 3610的tunnel  ip 出错信息如下：

No tunnel in the physical state of up was found for the packet. Dropped the packet.

在3610上ping 2811的tunnel ip 信息如下：

Ping 192.168.168.1 (192.168.168.1): 56 data bytes, press CTRL_C to break
*Sep 25 21:36:59:179 2018 MSR3610 GRE/7/packet:
 Tunnel0 packet: Before encapsulation according to adjacency table,
   192.168.168.2->192.168.168.1 (length = 84)
*Sep 25 21:36:59:179 2018 MSR3610 TUNNEL/7/packet:
 Tunnel dscp = 255. Inner tos = 0.
*Sep 25 21:36:59:179 2018 MSR3610 GRE/7/packet:
 Tunnel0 packet: After encapsulation,
   172.17.6.7->172.17.2.20 (length = 108)
Request time out
Request time out
Request time out
Request time out
Request time out

两边查看tunnel信息都是up

2811上的如下

Tunnel0 is up, line protocol is up
  Hardware is Tunnel
  Internet address is 192.168.168.1/24
  MTU 1514 bytes, BW 9 Kbit, DLY 500000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel source 172.17.2.20 (FastEthernet0/1), destination 172.17.6.7
  Tunnel protocol/transport GRE/IP
    Key disabled, sequencing disabled
    Checksumming of packets disabled
  Tunnel TTL 255
  Fast tunneling enabled
  Tunnel transmit bandwidth 8000 (kbps)
  Tunnel receive bandwidth 8000 (kbps)
  Last input 6d01h, output 00:03:50, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/0 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     0 packets input, 0 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     30 packets output, 3720 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out

msr3610的如下：

Tunnel0
Current state: UP
Line protocol state: UP
Description: Tunnel0 Interface
Bandwidth: 64 kbps
Maximum transmission unit: 1476
Internet address: 192.168.168.2/24 (primary)
Tunnel source 172.17.6.7 (Ethernet2/0), destination 172.17.2.20
Tunnel keepalive disabled
Tunnel TTL 255
Tunnel protocol/transport GRE/IP
    GRE key disabled
    Checksumming of GRE packets disabled
Output queue - Urgent queuing: Size/Length/Discards 0/1024/0
Output queue - Protocol queuing: Size/Length/Discards 0/500/0
Output queue - FIFO queuing: Size/Length/Discards 0/75/0
Last clearing of counters: Never
Last 300 seconds input rate: 0 bytes/sec, 0 bits/sec, 0 packets/sec
Last 300 seconds output rate: 0 bytes/sec, 0 bits/sec, 0 packets/sec
Input: 0 packets, 0 bytes, 0 drops
Output: 16 packets, 1312 bytes, 0 drops

应该怎么解决？