Hi,all.i use MikroTik RouterOS(v2.9.26) router made a sitetosite vpn to CISCO Router.Testing the IPsec tunnel is work.But when run after 24hr,the vpn will auto break off and need reboot the MikroTik router the vpn can re-connection.How to fix this issue?Thx. 
I’m having the same issue at the moment between a V5.3 and V6.3 firmware RouterBoard. The link is established, it sends data to the remote unit, but it isn’t receiving anything back. I have also rebooted both units but still it persists.
As a note, the V6 unit is on an ISP assigned dynamic PPPoE address and the V5 unit on a static IP.
Why are you using such an old version? (v2.9.26)
Is very strange,these is the router log when the IPsec tunnel is working after 12hours,some one can fix this issue?Thx a lot~
19:05:20 ipsec,ike,info received ISAKMP packet from 209.xxx.xxx.xxx:500, phase
2, Quick
19:05:20 ipsec,ike,info received ISAKMP packet from 209.xxx.xxx.xxx:500, phase
2, Quick
19:05:20 ipsec,ike,info received ISAKMP packet from 209.xxx.xxx.xxx:500, phase
2, Quick
19:06:04 ipsec,ike,info phase 1 expired (remote unknown)
19:06:04 ipsec,ike,info phase 1 expired (local 202.xxx.xxx.xxx:500) (remote
209.xxx.xxx.xxx:500)
19:06:05 ipsec,ike,info phase 1 deleted (local 202.xxx.xxx.xxx:500) (remote
209.xxx.xxx.xxx:500)
19:06:07 ipsec,ike,info received ISAKMP packet from 209.xxx.xxx.xxx:500, phase
2, Informational
19:06:07 ipsec,ike,info unexpected Informational exchange (remote unknown)
.
.
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Because the 2.9 is very stable and working fine,so i don’t upgrade to new version.You means upgrade to new version can fix this issue? 
Yeah,is very strange,the iIPsec tunnel show is established ,buy the log show a error:
ip ipsec policy> print stats
Flags: X - disabled, D - dynamic, I - invalid
0 src-address=192.168.184.0/24:any dst-address=192.168.220.0/24:any
protocol=all ph2-state=established in-accepted=0 in-dropped=0
out-accepted=0 out-dropped=1 encrypted=6 not-encrypted=0 decrypted=6
not-decrypted=0
1 src-address=192.168.184.0/24:any dst-address=192.168.112.0/24:any
protocol=all ph2-state=established in-accepted=0 in-dropped=0
out-accepted=0 out-dropped=0 encrypted=4 not-encrypted=0 decrypted=4
not-decrypted=0
2 src-address=192.168.184.0/24:any dst-address=192.168.104.0/24:any
protocol=all ph2-state=established in-accepted=0 in-dropped=0
out-accepted=0 out-dropped=0 encrypted=6 not-encrypted=0 decrypted=4
not-decrypted=0
router log:
10:33:20 ipsec,ike,info received ISAKMP packet from 209.xxx.xxx.xxx:500, phase
2, Quick
10:33:20 ipsec,ike,info responding phase 2 (src 202.xxx.xxx.xxx) (dst
209.XXX.XXX.XXX)
10:33:20 ipsec,ike,info no policy found (remote unknown)
10:33:20 ipsec,ike,info no proposal found (remote unknown)
10:33:20 ipsec,ike,info failed to pre-process packet (remote unknow