RB751 - Ethernet port crash, need to use another as WAN port

Hello.
One ethernet port on my RB751U 2HnD became out of service.
Problem is that this port is port 1, WAN port, named “Gateway” port in Winbox.
There is no link at physical layer, ADSL modem see no connection with RB751.
And LED od this port on RB751 glowing always, even if Ethernet port is empty.
So, I can’t receive IP by DHCP-client, and so on, Internet doesn’t work.

And my question is:
Can I reassign WAN port of my RB751, to another port? When another port (not port 1) acting as WAN port.

I tried following:
In Winbox

  1. In “Interfaces” set port 5 to be port without master port.
  2. In “DHCP client” set port to port 5.

But this doesn’t work, DHCP in “searching” status, but port 5 connected to ADSL modem with DHCP server.

Can this problem be solved, or I need to buy new RB751?

share your config with us.
The steps you took sound alright, maybe there is some other item that needs to be changed.

Here is my config:

[admin@MikroTik] > export

jan/02/1970 00:21:14 by RouterOS 5.20

software id = UUD8-8A24

/interface bridge
add admin-mac=D4:CA:6D:6B:5C:2B ageing-time=5m arp=enabled auto-mac=no disabled=no forward-delay=15s l2mtu=1598 max-message-age=20s mtu=1500 name=
bridge-local priority=0x8000 protocol-mode=rstp transmit-hold-count=6
/interface ethernet
set 0 arp=enabled auto-negotiation=yes disabled=yes full-duplex=yes l2mtu=1600 mac-address=D4:CA:6D:6B:5C:2A mtu=1500 name=ether1-gateway speed=
100Mbps
set 1 arp=enabled auto-negotiation=yes bandwidth=unlimited/unlimited disabled=no full-duplex=yes l2mtu=1598 mac-address=D4:CA:6D:6B:5C:2B
master-port=none mtu=1500 name=ether2-master-local speed=100Mbps
set 2 arp=enabled auto-negotiation=yes bandwidth=unlimited/unlimited disabled=no full-duplex=yes l2mtu=1598 mac-address=D4:CA:6D:6B:5C:2C
master-port=ether2-master-local mtu=1500 name=ether3-slave-local speed=100Mbps
set 3 arp=enabled auto-negotiation=yes bandwidth=unlimited/unlimited disabled=no full-duplex=yes l2mtu=1598 mac-address=D4:CA:6D:6B:5C:2D
master-port=ether2-master-local mtu=1500 name=ether4-slave-local speed=100Mbps
set 4 arp=enabled auto-negotiation=yes bandwidth=unlimited/unlimited disabled=no full-duplex=yes l2mtu=1598 mac-address=D4:CA:6D:6B:5C:2E
master-port=none mtu=1500 name=ether5-newgtw speed=100Mbps
/interface ethernet switch
set 0 mirror-source=none mirror-target=none name=switch1
/interface wireless security-profiles
set [ find default=yes ] authentication-types=“” eap-methods=passthrough group-ciphers=aes-ccm group-key-update=5m interim-update=0s
management-protection=disabled management-protection-key=“” mode=none name=default radius-eap-accounting=no radius-mac-accounting=no
radius-mac-authentication=no radius-mac-caching=disabled radius-mac-format=XX:XX:XX:XX:XX:XX radius-mac-mode=as-username static-algo-0=none
static-algo-1=none static-algo-2=none static-algo-3=none static-key-0=“” static-key-1=“” static-key-2=“” static-key-3=“”
static-sta-private-algo=none static-sta-private-key=“” static-transmit-key=key-0 supplicant-identity=MikroTik tls-certificate=none tls-mode=
no-certificates unicast-ciphers=aes-ccm wpa-pre-shared-key=“” wpa2-pre-shared-key=“”
/interface wireless
set 0 adaptive-noise-immunity=none allow-sharedkey=no antenna-gain=0 antenna-mode=ant-a area=“” arp=enabled band=2ghz-b/g/n basic-rates-a/g=6Mbps
basic-rates-b=1Mbps bridge-mode=enabled channel-width=20/40mhz-ht-above compression=no country=no_country_set default-ap-tx-limit=0
default-authentication=yes default-client-tx-limit=0 default-forwarding=yes dfs-mode=none disable-running-check=no disabled=no
disconnect-timeout=3s distance=indoors frame-lifetime=0 frequency=2412 frequency-mode=manual-txpower frequency-offset=0 hide-ssid=no
ht-ampdu-priorities=0 ht-amsdu-limit=8192 ht-amsdu-threshold=8192 ht-basic-mcs=mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7
ht-guard-interval=any ht-rxchains=0,1 ht-supported-mcs=“mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7,mcs-8,mcs-9,mcs-10,mcs-11,mcs-12,mcs-13,
mcs-14,mcs-15,mcs-16,mcs-17,mcs-18,mcs-19,mcs-20,mcs-21,mcs-22,mcs-23” ht-txchains=0,1 hw-fragmentation-threshold=disabled hw-protection-mode=
none hw-protection-threshold=0 hw-retries=7 l2mtu=2290 mac-address=D4:CA:6D:6B:5C:2F max-station-count=2007 mode=ap-bridge mtu=1500
multicast-helper=default name=wlan1 noise-floor-threshold=default nv2-cell-radius=30 nv2-noise-floor-offset=default nv2-preshared-key=“”
nv2-qos=default nv2-queue-count=2 nv2-security=disabled on-fail-retry-time=100ms periodic-calibration=default periodic-calibration-interval=60
preamble-mode=both proprietary-extensions=post-2.9.25 radio-name=D4CA6D6B5C2F rate-selection=advanced rate-set=default scan-list=default
security-profile=default ssid=MikroTik station-bridge-clone-mac=00:00:00:00:00:00 supported-rates-a/g=
6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps supported-rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps tdma-period-size=2 tx-power-mode=default
update-stats-interval=disabled wds-cost-range=50-150 wds-default-bridge=none wds-default-cost=100 wds-ignore-ssid=no wds-mode=disabled
wireless-protocol=any wmm-support=disabled
/interface wireless manual-tx-power-table
set wlan1 manual-tx-powers=“1Mbps:17,2Mbps:17,5.5Mbps:17,11Mbps:17,6Mbps:17,9Mbps:17,12Mbps:17,18Mbps:17,24Mbps:17,36Mbps:17,48Mbps:17,54Mbps:17,HT2
0-0:17,HT20-1:17,HT20-2:17,HT20-3:17,HT20-4:17,HT20-5:17,HT20-6:17,HT20-7:17,HT40-0:17,HT40-1:17,HT40-2:17,HT40-3:17,HT40-4:17,HT40-5:17,HT40-6:
17,HT40-7:17”
/interface wireless nstreme
set wlan1 disable-csma=no enable-nstreme=no enable-polling=yes framer-limit=3200 framer-policy=none
/ip hotspot profile
set [ find default=yes ] dns-name=“” hotspot-address=0.0.0.0 html-directory=hotspot http-cookie-lifetime=3d http-proxy=0.0.0.0:0 login-by=
cookie,http-chap name=default rate-limit=“” smtp-server=0.0.0.0 split-user-domain=no use-radius=no
/ip hotspot user profile
set [ find default=yes ] idle-timeout=none keepalive-timeout=2m name=default shared-users=1 status-autorefresh=1m transparent-proxy=no
/ip ipsec proposal
set [ find default=yes ] auth-algorithms=sha1 disabled=no enc-algorithms=3des lifetime=30m name=default pfs-group=modp1024
/ip pool
add name=default-dhcp ranges=192.168.88.10-192.168.88.254
/ip dhcp-server
add address-pool=default-dhcp authoritative=after-2sec-delay bootp-support=static disabled=no interface=bridge-local lease-time=3d name=default
/ppp profile
set 0 change-tcp-mss=yes name=default only-one=default use-compression=default use-encryption=default use-mpls=default use-vj-compression=default
set 1 change-tcp-mss=yes name=default-encryption only-one=default use-compression=default use-encryption=yes use-mpls=default use-vj-compression=
default
/queue type
set 0 kind=pfifo name=default pfifo-limit=50
set 1 kind=pfifo name=ethernet-default pfifo-limit=50
set 2 kind=sfq name=wireless-default sfq-allot=1514 sfq-perturb=5
set 3 kind=red name=synchronous-default red-avg-packet=1000 red-burst=20 red-limit=60 red-max-threshold=50 red-min-threshold=10
set 4 kind=sfq name=hotspot-default sfq-allot=1514 sfq-perturb=5
set 5 kind=none name=only-hardware-queue
set 6 kind=mq-pfifo mq-pfifo-limit=50 name=multi-queue-ethernet-default
set 7 kind=pfifo name=default-small pfifo-limit=10
/routing bgp instance
set default as=65530 client-to-client-reflection=yes disabled=no ignore-as-path-len=no name=default out-filter=“” redistribute-connected=no
redistribute-ospf=no redistribute-other-bgp=no redistribute-rip=no redistribute-static=no router-id=0.0.0.0 routing-table=“”
/routing ospf instance
set [ find default=yes ] disabled=no distribute-default=never in-filter=ospf-in metric-bgp=auto metric-connected=20 metric-default=1
metric-other-ospf=auto metric-rip=20 metric-static=20 name=default out-filter=ospf-out redistribute-bgp=no redistribute-connected=no
redistribute-other-ospf=no redistribute-rip=no redistribute-static=no router-id=0.0.0.0
/routing ospf area
set [ find default=yes ] area-id=0.0.0.0 disabled=no instance=default name=backbone type=default
/snmp community
set [ find default=yes ] addresses=0.0.0.0/0 authentication-password=“” authentication-protocol=MD5 encryption-password=“” encryption-protocol=DES
name=public read-access=yes security=none write-access=no
/system logging action
set 0 memory-lines=100 memory-stop-on-full=no name=memory target=memory
set 1 disk-file-count=2 disk-file-name=log disk-lines-per-file=100 disk-stop-on-full=no name=disk target=disk
set 2 name=echo remember=yes target=echo
set 3 bsd-syslog=no name=remote remote-port=514 src-address=0.0.0.0 syslog-facility=daemon syslog-severity=auto target=remote
/user group
set read name=read policy=local,telnet,ssh,reboot,read,test,winbox,password,web,sniff,sensitive,api,!ftp,!write,!policy skin=default
set write name=write policy=local,telnet,ssh,reboot,read,write,test,winbox,password,web,sniff,sensitive,api,!ftp,!policy skin=default
set full name=full policy=local,telnet,ssh,ftp,reboot,read,write,policy,test,winbox,password,web,sniff,sensitive,api skin=default
/interface bridge port
add bridge=bridge-local disabled=no edge=auto external-fdb=auto horizon=none interface=ether2-master-local path-cost=10 point-to-point=auto
priority=0x80
add bridge=bridge-local disabled=no edge=auto external-fdb=auto horizon=none interface=wlan1 path-cost=10 point-to-point=auto priority=0x80
/interface bridge settings
set use-ip-firewall=no use-ip-firewall-for-pppoe=no use-ip-firewall-for-vlan=no
/interface ethernet switch port
set 0 vlan-header=leave-as-is vlan-mode=fallback
set 1 vlan-header=leave-as-is vlan-mode=fallback
set 2 vlan-header=leave-as-is vlan-mode=fallback
set 3 vlan-header=leave-as-is vlan-mode=fallback
set 4 vlan-header=leave-as-is vlan-mode=fallback
/interface l2tp-server server
set authentication=pap,chap,mschap1,mschap2 default-profile=default-encryption enabled=no max-mru=1460 max-mtu=1460 mrru=disabled
/interface ovpn-server server
set auth=sha1,md5 certificate=none cipher=blowfish128,aes128 default-profile=default enabled=no keepalive-timeout=60 mac-address=FE:D5:C2:EE:78:FF
max-mtu=1500 mode=ip netmask=24 port=1194 require-client-certificate=no
/interface pptp-server server
set authentication=mschap1,mschap2 default-profile=default-encryption enabled=no keepalive-timeout=30 max-mru=1460 max-mtu=1460 mrru=disabled
/interface sstp-server server
set authentication=pap,chap,mschap1,mschap2 certificate=none default-profile=default enabled=no keepalive-timeout=60 max-mru=1500 max-mtu=1500
mrru=disabled port=443 verify-client-certificate=no
/interface wireless align
set active-mode=yes audio-max=-20 audio-min=-100 audio-monitor=00:00:00:00:00:00 filter-mac=00:00:00:00:00:00 frame-size=300 frames-per-second=25
receive-all=no ssid-all=no
/interface wireless sniffer
set channel-time=200ms file-limit=10 file-name=“” memory-limit=10 multiple-channels=no only-headers=no receive-errors=no streaming-enabled=no
streaming-max-rate=0 streaming-server=0.0.0.0
/interface wireless snooper
set channel-time=200ms multiple-channels=yes receive-errors=no
/ip accounting
set account-local-traffic=no enabled=no threshold=256
/ip accounting web-access
set accessible-via-web=no address=0.0.0.0/0
/ip address
add address=192.168.88.1/24 comment=“default configuration” disabled=no interface=bridge-local network=192.168.88.0
/ip dhcp-client
add add-default-route=yes comment=“default configuration” default-route-distance=1 disabled=no interface=ether5-newgtw use-peer-dns=yes
use-peer-ntp=yes
/ip dhcp-server config
set store-leases-disk=5m
/ip dhcp-server network
add address=192.168.88.0/24 comment=“default configuration” dhcp-option=“” dns-server=192.168.88.1 gateway=192.168.88.1 ntp-server=“” wins-server=
“”
/ip dns
set allow-remote-requests=yes cache-max-ttl=1w cache-size=2048KiB max-udp-packet-size=4096 servers=“”
/ip dns static
add address=192.168.88.1 disabled=no name=router ttl=1d
/ip firewall connection tracking
set enabled=yes generic-timeout=10m icmp-timeout=10s tcp-close-timeout=10s tcp-close-wait-timeout=10s tcp-established-timeout=1d
tcp-fin-wait-timeout=10s tcp-last-ack-timeout=10s tcp-syn-received-timeout=5s tcp-syn-sent-timeout=5s tcp-syncookie=no tcp-time-wait-timeout=
10s udp-stream-timeout=3m udp-timeout=10s
/ip firewall filter
add action=accept chain=input comment=“default configuration” disabled=no protocol=icmp
add action=accept chain=input comment=“default configuration” connection-state=established disabled=no
add action=accept chain=input comment=“default configuration” connection-state=related disabled=no
add action=drop chain=input comment=“default configuration” disabled=no in-interface=ether1-gateway
/ip firewall nat
add action=masquerade chain=srcnat comment=“default configuration” disabled=no out-interface=ether1-gateway to-addresses=0.0.0.0
/ip firewall service-port
set ftp disabled=no ports=21
set tftp disabled=no ports=69
set irc disabled=no ports=6667
set h323 disabled=no
set sip disabled=no ports=5060,5061 sip-direct-media=yes
set pptp disabled=no
/ip hotspot service-port
set ftp disabled=no ports=21
/ip neighbor discovery
set ether1-gateway disabled=yes
set ether2-master-local disabled=no
set ether3-slave-local disabled=no
set ether4-slave-local disabled=no
set ether5-newgtw disabled=no
set wlan1 disabled=yes
set bridge-local disabled=no
/ip proxy
set always-from-cache=no cache-administrator=webmaster cache-hit-dscp=4 cache-on-disk=no enabled=no max-cache-size=none max-client-connections=600
max-fresh-time=3d max-server-connections=600 parent-proxy=0.0.0.0 parent-proxy-port=0 port=8080 serialize-connections=no src-address=0.0.0.0
/ip service
set telnet address=“” disabled=no port=23
set ftp address=“” disabled=no port=21
set www address=“” disabled=no port=80
set ssh address=“” disabled=no port=22
set www-ssl address=“” certificate=none disabled=yes port=443
set api address=“” disabled=yes port=8728
set winbox address=“” disabled=no port=8291
/ip smb
set allow-guests=yes comment=MikrotikSMB domain=MSHOME enabled=no interfaces=all
/ip smb shares
set [ find default=yes ] comment=“default share” directory=/pub disabled=no max-sessions=10 name=pub
/ip smb users
set [ find default=yes ] disabled=no name=guest password=“” read-only=yes
/ip socks
set connection-idle-timeout=2m enabled=no max-connections=200 port=1080
/ip traffic-flow
set active-flow-timeout=30m cache-entries=4k enabled=no inactive-flow-timeout=15s interfaces=all
/ip upnp
set allow-disable-external-interface=yes enabled=no show-dummy-rule=yes
/mpls
set dynamic-label-range=16-1048575 propagate-ttl=yes
/mpls interface
set [ find default=yes ] disabled=no interface=all mpls-mtu=1508
/mpls ldp
set distribute-for-default-route=no enabled=no hop-limit=255 loop-detect=no lsr-id=0.0.0.0 path-vector-limit=255 transport-address=0.0.0.0
use-explicit-null=no
/port firmware
set directory=firmware ignore-directip-modem=no
/ppp aaa
set accounting=yes interim-update=0s use-radius=no
/queue interface
set ether1-gateway queue=only-hardware-queue
set ether2-master-local queue=only-hardware-queue
set ether3-slave-local queue=only-hardware-queue
set ether4-slave-local queue=only-hardware-queue
set ether5-newgtw queue=only-hardware-queue
set wlan1 queue=wireless-default
/radius incoming
set accept=no port=3799
/routing bfd interface
set [ find default=yes ] disabled=no interface=all interval=0.2s min-rx=0.2s multiplier=5
/routing mme
set bidirectional-timeout=2 gateway-class=none gateway-keepalive=1m gateway-selection=no-gateway origination-interval=5s preferred-gateway=0.0.0.0
timeout=1m ttl=50
/routing rip
set distribute-default=never garbage-timer=2m metric-bgp=1 metric-connected=1 metric-default=1 metric-ospf=1 metric-static=1 redistribute-bgp=no
redistribute-connected=no redistribute-ospf=no redistribute-static=no routing-table=main timeout-timer=3m update-timer=30s
/snmp
set contact=“” enabled=no engine-id=“” location=“” trap-generators=“” trap-target=“” trap-version=1
/system clock
set time-zone-name=manual
/system clock manual
set dst-delta=+00:00 dst-end=“jan/01/1970 00:00:00” dst-start=“jan/01/1970 00:00:00” time-zone=+00:00
/system identity
set name=MikroTik
/system leds
set 0 disabled=no interface=wlan1 leds=wlan-led type=wireless-status
/system logging
set 0 action=memory disabled=no prefix=“” topics=info
set 1 action=memory disabled=no prefix=“” topics=error
set 2 action=memory disabled=no prefix=“” topics=warning
set 3 action=echo disabled=no prefix=“” topics=critical
/system note
set note=“” show-at-login=yes
/system ntp client
set enabled=yes mode=unicast primary-ntp=94.242.49.220 secondary-ntp=95.140.150.140
/system resource irq
set 0 cpu=auto
set 1 cpu=auto
set 2 cpu=auto
set 3 cpu=auto
/system routerboard settings
set boot-device=nand-if-fail-then-ethernet boot-protocol=bootp cpu-frequency=400MHz force-backup-booter=no silent-boot=no
/system upgrade mirror
set check-interval=1d enabled=no primary-server=0.0.0.0 secondary-server=0.0.0.0 user=“”
/system watchdog
set auto-send-supout=no automatic-supout=yes no-ping-delay=5m watch-address=none watchdog-timer=yes
/tool bandwidth-server
set allocate-udp-ports-from=2000 authenticate=yes enabled=yes max-sessions=100
/tool e-mail
set address=0.0.0.0 from=<> password=“” port=25 starttls=no user=“”
/tool graphing
set page-refresh=300 store-every=5min
/tool mac-server
set [ find default=yes ] disabled=yes interface=all
add disabled=no interface=ether2-master-local
add disabled=no interface=ether3-slave-local
add disabled=no interface=ether4-slave-local
add disabled=no interface=ether5-newgtw
add disabled=no interface=wlan1
add disabled=no interface=bridge-local
/tool mac-server mac-winbox
set [ find default=yes ] disabled=yes interface=all
add disabled=no interface=ether2-master-local
add disabled=no interface=ether3-slave-local
add disabled=no interface=ether4-slave-local
add disabled=no interface=ether5-newgtw
add disabled=no interface=wlan1
add disabled=no interface=bridge-local
/tool mac-server ping
set enabled=yes
/tool sms
set allowed-number=“” channel=0 keep-max-sms=0 receive-enabled=no secret=“”
/tool sniffer
set file-limit=1000KiB file-name=“” filter-ip-address=“” filter-ip-protocol=“” filter-mac-address=“” filter-mac-protocol=“” filter-port=“”
filter-stream=yes interface=all memory-limit=100KiB memory-scroll=yes only-headers=no streaming-enabled=no streaming-server=0.0.0.0
/tool traffic-generator
set latency-distribution-scale=10 test-id=0
/user aaa
set accounting=yes default-group=read exclude-groups=“” interim-update=0s use-radius=no
[admin@MikroTik] >

You should change your NAT rule to reflect the changed output port
/ip firewall nat
add action=masquerade chain=srcnat comment=“default configuration” disabled=no out-interface=ether1-gateway to-addresses=0.0.0.0Change ether1-gateway to the port now used as wan interface

Also your last firewall rule should be changed
/ip firewall filter
add action=drop chain=input comment=“default configuration” disabled=no in-interface=ether1-gateway

Thank you very much!
I’ll try this.

Maybe a reboot of the router will also help.
Since you connected a different port, the ISP will see a different MAC address, maybe that needs some time too.

It works, thank you again.