I have mikrotik 2.9.45 version configure by one engineer who have left the company.It is configure as dhcp, NAT and firewall. We have a change of IP ADDRESS. Pls can somebody help me on how to change it to the new ip , gateway and DNS ?

Should not be a problem. I use ssh to manage my MT boxes.

/ip address
add address=xx.xx.xx.xx/xx interface=ether1

/ip route add gateway=xx.xx.xx.yy

/ip dns
set primary-dns=zz.zz.zz.zz
set secondary-dns=ww.ww.ww.ww

Replace all with appropriate settings. Remove the old settings once the new ones operate ok.

Thanks for your reply. If i implement all this command script with the new set of IP paramenter, won't it remove the old IPs ? OR How do I remove the Old onces after implementation. thanks

Inserting the new ips will not remove anything. The old ips should remain and working until you remove them.
/ip address
print
remove X

Replace X with the line number of the ip you wish to remove. Same with the gateway.

Thanks once again. Now inserting the new ips with the old once in place, will it work with the new ip settings without removing the old onces ?

Yes. It should work with both ips.

ADD: The one it uses is normally determined by the masquerade or srcnat in "/ip firewall nat". If you use the masquerade rule rather than src-nat, the results may be unpredictable until you remove all but one ip from that interface.

AM greatful, I will implement this then get back to you later.

It works after removing the former gatway IP.
thanks once again.
bye