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Problems with GRE tunnel connection to mikrotik

Ivane Sajaia
Im having problem with GRE tunnel connecting cisco and mikrotik routers, have tried many different configurations but none seems to work,
tried disabling firewall rules on mikrotik,  tried to turn off keepalive on mikrotik gre, tried to keep it on and configured same keepalive on cisco but still didnt work, tried with ipsec but no results.
also tried adjusting MTU to first 1476 then 1400 on both ends but still nothing
currently im just trying to get gre in up state, configuration is really simple
interface tunnel 1
 tunnel source
 tunnel destination
 ip address
same on mikrotik
on both routers GRE is easily up when its connecting to other devices, i have tried mikrotik to mikrotik and cisco to other mikrotik and works perfecting also on these routers there are currently many tunnels that are working fine....
Router info:
Mikrotik: RB951G-2HnD  firmware:6.45.7
Cisco:  CISCO2921/K9,   Version 15.7(3)M3
Thanks in advance
2 Replies 2

Jaderson Pessoa

post here the output from:

show ip int brief
show run int tun 1
show int tun 1
Jaderson Pessoa
*** Rate All Helpful Responses ***

show ip interface brief

 status - up

 protocol - up


show run interface tunnel 1

 tunnel source
 tunnel destination
 ip address 
 ip mtu 1400
 ip tcp adjust-mss 1360 
show interface tunnel 1
 Hardware is Tunnel
  Description: TEST
  Internet address is
  MTU 17916 bytes, BW 100 Kbit/sec, DLY 50000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel linestate evaluation up
  Tunnel source, destination
  Tunnel protocol/transport GRE/IP
    Key disabled, sequencing disabled
    Checksumming of packets disabled
  Tunnel TTL 255, Fast tunneling enabled
  Tunnel transport MTU 1476 bytes
  Tunnel transmit bandwidth 8000 (kbps)
  Tunnel receive bandwidth 8000 (kbps)
  Last input never, output 04:05:36, output hang never
  Last clearing of "show interface" counters 05:43:03
  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 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     3441 packets output, 282721 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
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