Конфигурация Cisco

interface Tunnel881021
 description Mik01-Center_SEC-PRI
 ip address 192.168.252.37 255.255.255.252
 no ip redirects
 no ip unreachables
 no ip proxy-arp
 ip mtu 1450
 ip ospf network point-to-point
 tunnel source 90.154.206.114
 tunnel mode ipip
 tunnel destination 62.105.249.228
!
router ospf 15
 router-id 192.168.253.11
 passive-interface default
 no passive-interface Tunnel881021
 network 192.168.252.36 0.0.0.3 area 0

Конфигурация Mikrotik

За основу можно взять стандартный Изначальный конфиг микрота

/interface ipip
add !keepalive local-address=62.105.249.228 mtu=1450 name=Tunnel1 remote-address=90.154.206.114
/ip address
add address=192.168.252.38/30 interface=Tunnel1 network=192.168.252.36
/routing ospf network
add area=backbone network=192.168.252.36/30
add area=backbone network=192.168.88.0/24

Разрешения Firewall

Cisco

permit ipinip any any

Mikrotik

add chain=input protocol=ipip