Customer set up ospf peer through DSVPN tunnel and PPPoE on AR160, but always stop at exchange state.The peer IP address of tunnel interface can access by ping and there is not packet loss.

NA

Checking the state of OSPF peer state and it always stop at exchange state.
[AR160]display ospf peer Tunnel 0/0/0
OSPF Process 10 with Router ID 10.130.253.166
Neighbors
Area 0.0.0.130 interface 10.130.253.166(Tunnel0/0/0)'s neighbors
Router ID: 3.2.3.2 Address: 10.130.253.1
State: Exchange Mode:Nbr is Slave Priority: 100
DR: None BDR: None MTU: 0
Dead timer due in 99 sec
Retrans timer interval: 5
Neighbor is up for 00:00:00
Authentication Sequence: [ 0 ]
Checking the cumulative of ospf, find out that the AR160 send out DB Description packet but no feedback. Output is increase but input don't change.
[AR160-diagnose]display ospf cumulative
OSPF Process 10 with Router ID 10.130.253.166
Cumulations
IO Statistics
Type Input Output
Hello 90 170
DB Description 16 295
Link-State Req 0 13
Link-State Update 1548 142
Link-State Ack 35 798
ASE: 98 Checksum Sum: 10465619
LSAs originated by this router
Ping with big packet, find out the biggest packet can go through is 1350.
[AR160]ping -f -s 1350 10.130.253.1
PING 10.130.253.1: 1350 data bytes, press CTRL_C to break
Reply from 10.130.253.1: bytes=1350 Sequence=1 ttl=255 time=12 ms
Reply from 10.130.253.1: bytes=1350 Sequence=2 ttl=255 time=12 ms
Reply from 10.130.253.1: bytes=1350 Sequence=3 ttl=255 time=12 ms
Reply from 10.130.253.1: bytes=1350 Sequence=4 ttl=255 time=12 ms
--- 10.130.253.1 ping statistics ---
4 packet(s) transmitted
4 packet(s) received
0.00% packet loss
round-trip min/avg/max = 12/12/12 ms
<AR160>ping -s 1400 10.130.253.2
PING 10.130.253.2: 1400 data bytes, press CTRL_C to break
Request time out
Request time out
Request time out
--- 10.130.253.2 ping statistics ---
3 packet(s) transmitted
0 packet(s) received
100.00% packet loss
Checking the MTU of DSVPN tunnel interface and PPPoE interface, both of them is 1500.
<AR161>display interface tunnel 0/0/0
Tunnel0/0/0 current state : UP
Line protocol current state : UP
Last line protocol up time : 2017-10-23 03:11 UTC+08:00
Description:Connect to MPC, OIS AR1220
Route Port,The Maximum Transmit Unit is 1500
Internet Address is 10.130.253.64/24
Encapsulation is TUNNEL, loopback not set
Tunnel source Dialer1
Tunnel protocol/transport P2MP-GRE/IP, key enabled
Checksumming of packets disabled
Current system time: 2017-10-23 03:11+08:00
300 seconds input rate 0 bits/sec, 0 packets/sec
300 seconds output rate 568 bits/sec, 0 packets/sec
0 seconds input rate 0 bits/sec, 0 packets/sec
0 seconds output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes
0 input error
123681 packets output, 16021278 bytes
0 output error
Input bandwidth utilization : 0%
Output bandwidth utilization : 0%
<AR160>display interface Dialer1
Dialer1 current state : UP
Line protocol current state : UP (spoofing)
Description:HUAWEI, AR Series, Dialer1 Interface
Route Port,The Maximum Transmit Unit is 1500, Hold timer is 10(sec)
Internet Address is negotiated, 116.48.155.109/32
Link layer protocol is PPP
LCP initial
Physical is Dialer
Current system time: 2017-10-23 03:11+08:00
Last 300 seconds input rate 0 bits/sec, 0 packets/sec
Last 300 seconds output rate 0 bits/sec, 0 packets/sec
Realtime 0 seconds input rate 0 bits/sec, 0 packets/sec
Realtime 0 seconds output rate 0 bits/sec, 0 packets/sec
Input: 0 bytes
Output:0 bytes
Input bandwidth utilization : 0%
Output bandwidth utilization : 0%

the MTU of DSVPN tunnel interface is too big, cause the OSPF DB Description packets can’t go through the PPPoE interface.

Change the MTU of DSVPN tunnel interface to 1200.
#
interface Tunnel0/0/0
mtu 1200
#
After change the MTU of tunnel interface, the ospf peer state change to full.
<AR160>dis ospf peer brief
OSPF Process 10 with Router ID 10.130.253.166
Peer Statistic Information
----------------------------------------------------------------------------
Area Id Interface Neighbor id State
0.0.0.130 Tunnel0/0/0 3.2.3.2 Full
0.0.0.130 Tunnel0/0/0 10.1.11.241 Full
----------------------------------------------------------------------------

If the OSPF peer stop at exchange state, please check whether the MTU of interface is suitable or not.