A really strange thing to my Mikrotik gateway.
when i issued the command
ip route print
it showed me that the route is unreachable by using word “u”. and all of sudden, clients cannot access the internet!

- i checked the NIC, it’s work fine
- i check the cable, it also work fine
- I put other router i.e Linksys and it’s work fine.
can something tell me what’s the problem?
Can you post a copy of the routing table and the IP address? Which ROS version and platform are you using?
i m using 3.30
ip address
WAN:x03.1x5.xx.214/30
gateway; x03.1x5.xx.213
LAN;192.168.1.1
for static entry it shows like this:
S 0.0.0.0/0 u x03.1x5.xx.214 before it showed WAN in interface list but now it is blank
it might be on the routing table.
please provide “/ip route print” result
or you can try using the interface name not the ip.
CMIIW 
I solved the problem by replacing the LAN card , delete the gateway, re-enter the gateway then restart and it work fine now.