Intermittent Internet disconnect and reconnect

tushar · October 29, 2025, 9:45am

After 2 years usage suddenly (nothing changed nothing configured), ISP WAN_1 Internet keep disconnecting after every 40 to 45 minutes for 20 to 25 seconds, Cross checked WAN_1 ISP to laptop(Direct) configuring static IP working fine no issues, ISP to Mikrotik Router internet intermittent disconnection begins.

Congiguration used:-

Two ISP primary WAN_1 and Secondary WAN_3 using NETWATCH, Failover, PCC. ISP WAN_3 Second no issues at all.

Model : RB750Gr3

Firmware Type : mt7621L

Factory Firmware : 6.47.8

Current Firmware : 6.47.8

Upgrade Firmware : 6.47.8

memelchenkov · October 29, 2025, 10:29am

Call ISP support so they fix the cable or their house switch. Sounds like it is on ISP side.

tushar · October 29, 2025, 10:44am

but when i connect laptop/Desktop directly to my ISP Provided router never disconnects even if i use Cisco RV042 Router no issue, only with mikrotik having this issue. how can i say ISP side problem.

jaclaz · October 29, 2025, 11:06am

Since you haven't changed your configuration, nor uprdated the Mikrotik RouterOS, only two possibilities remain:

a hardware issue on the specific device (but RB750GR3's are re-known for their durability)
the ISP changed something in the way they deliver internet to you and this something is compatible with other devices but not with your (old) settings on the Mikrotik

Checking #2 first seems logical.

mkx · October 29, 2025, 2:01pm

Another possibility:

power adapter of your router aged enough to become marginal. So replace PA with a suitable power characterictics (voltage within 8V-30V interval, I'd go with 12V as it makes less stress on internal DC-DC down-converters; power output equal or slightly higher than original, which was slightly above 9W ... so if going with 12V, 1.5A should be plenty).

tushar · October 29, 2025, 4:22pm

As i said earlier my second WAN_2 Connection works perfectly no disconnections runs smoothly issue with WAN_1 Connection. If power adapter having issue then both WAN_1 and WAN_2 drops internet connections.

mkx · October 29, 2025, 4:33pm

Not necessarily, it might depend on physical link peer and cable connecting the two. One link might require higher Tx power than the other one and with iffy PA one never knows what kind of problems will arise.

tushar · October 29, 2025, 6:29pm

same problem power adapter changed issue remain as it is…..

rplant · October 30, 2025, 9:08am

You could send a polite email to the ISP and ask if something has changed at all.

You could swap the WAN configs over (so ether that was WAN2 becomes WAN1 and ether that was WAN1 becomes WAN2) and see if the problem stays on the same physical interface, or disappears, or stays with the ISP, or perhaps causes both interfaces to be unreliable. :(

memelchenkov · October 30, 2025, 9:26am

Actually he can’t send email to ISP. He probably even can’t ask for a tech from them. It is India, I am aware how ISPs work there… unfortunately.

tushar · November 2, 2025, 7:19am

i did but as per them nothing changed from there side, as i discovered when i connect direct to computer laptop/desktop and any other router works flawlessly no connection drops.

memelchenkov · November 2, 2025, 10:48am

Show disconnect logs.

tushar · November 2, 2025, 12:47pm

Logs disconnection & Reconnection

jaclaz · November 2, 2025, 12:57pm

It seems like you have something changing routes that cause the disconnection.

Before each disconnection there are two route changed, and before each re-connection, there are as well two routes changed.

Post your complete configuration for review, following these instructions:

tushar · November 2, 2025, 1:48pm

This is due to NETWATCH Script im using

#ISP1

ip route disable [find dst-address=0.0.0.0/0 gateway=10.1.1.1]
:log error "ISP1 is down"
/ip firewall connection remove [find]

ip route enable [find dst-address=0.0.0.0/0 gateway=10.1.1.1]
:log warning "ISP1 is up"

#ISP2

ip route disable [find dst-address=0.0.0.0/0 gateway=10.2.2.1]
:log error "ISP2 is down"
/ip firewall connection remove [find]

ip route enable [find dst-address=0.0.0.0/0 gateway=10.2.2.1]
:log warning "ISP2 is up"

#ISP3

ip route disable [find dst-address=0.0.0.0/0 gateway=10.3.3.1]
:log error "ISP3 is down"
/ip firewall connection remove [find]

ip route enable [find dst-address=0.0.0.0/0 gateway=10.3.3.1]
:log warning "ISP3 is up"

memelchenkov · November 2, 2025, 1:57pm

If you ping ISP’s gateway then don’t do it. Gateways usually don’t guarantee 100% replies on ICMP.

tushar · November 2, 2025, 2:28pm

# nov/02/2025 19:36:35 by RouterOS 6.47.8
# software id = rtrt-gfgf
#
# model = RB750Gr3
# serial number = rtwetete345
/interface bridge
add name=bridge1
/interface ethernet
set [ find default-name=ether1 ] comment=Airtel name=ether1_WAN1
set [ find default-name=ether2 ] comment=ACT name=ether2_WAN2
set [ find default-name=ether3 ] comment=Jio name=ether3_WAN3
set [ find default-name=ether4 ] comment=Bridge
set [ find default-name=ether5 ] comment="AMD B350"
/interface list
add name=WAN
add name=LAN
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/ip hotspot profile
set [ find default=yes ] html-directory=flash/hotspot
/ip pool
add name=dhcp ranges=192.168.1.2-192.168.1.254
/ip dhcp-server
add address-pool=dhcp disabled=no interface=bridge1 lease-time=3d name=dhcp1
/interface bridge port
add bridge=bridge1 interface=ether4
add bridge=bridge1 interface=ether5
/interface detect-internet
set internet-interface-list=WAN lan-interface-list=LAN wan-interface-list=WAN
/interface list member
add interface=ether1_WAN1 list=WAN
add interface=bridge1 list=LAN
add interface=ether2_WAN2 list=WAN
add interface=ether3_WAN3 list=WAN
/ip address
add address=223.239.128.14/24 comment=AirTel interface=ether1_WAN1 network=\
    223.239.128.0
add address=49.205.176.189/24 comment=ACT disabled=yes interface=ether2_WAN2 \
    network=49.205.176.0
add address=192.168.29.3/24 comment="Jio Fiber" interface=ether3_WAN3 \
    network=192.168.29.0
add address=192.168.1.1/24 comment=LAN interface=bridge1 network=192.168.1.0
/ip arp
add address=192.168.1.42 interface=bridge1 mac-address=asdfsdfsdfs
add address=192.168.1.14 interface=bridge1 mac-address=asdfsfasfasf
add address=192.168.1.2 interface=bridge1 mac-address=asdfasfsafasf
/ip dhcp-server lease
add address=192.168.1.14 client-id=asfsafsadfsadfas comment="imou 2E" \
    mac-address=sadfsafsfsafsadfasf server=dhcp1
add address=192.168.1.42 client-id=sdfsfsafsafsfd comment=\
    "Ranger2Grey Wired" mac-address=asfdsafsafsadfsa server=dhcp1
add address=192.168.1.54 client-id=adfsadfasfsfsadf mac-address=\
    asdfasdfsafasf server=dhcp1
add address=192.168.1.41 client-id=1:sdfsfsafdasf mac-address=\
    asdfasfasfa server=dhcp1
/ip dhcp-server network
add address=192.168.1.0/24 gateway=192.168.1.1
/ip dns
set allow-remote-requests=yes use-doh-server=\
    https://cloudflare-dns.com/dns-query verify-doh-cert=yes
/ip dns static
add address=104.16.248.249 name=cloudflare-dns.com
add address=104.16.249.249 name=cloudflare-dns.com
/ip firewall filter
add action=drop chain=output comment=Airtel_WAN_1 disabled=yes dst-address=\
    8.8.8.8 protocol=icmp
add action=drop chain=output comment=WAN_2 dst-address=9.9.9.9 protocol=icmp
add action=drop chain=output comment=Jio_WAN_3 disabled=yes dst-address=\
    8.8.4.4 protocol=icmp
add action=drop chain=output comment="deny icmp packet to 8.8.4.4 via wan1" \
    disabled=yes dst-address=8.8.4.4 out-interface=ether1_WAN1 protocol=icmp
add action=drop chain=output comment="deny icmp packet to 8.8.4.4 via wan2" \
    disabled=yes dst-address=8.8.4.4 out-interface=ether2_WAN2 protocol=icmp
add action=drop chain=output comment="deny icmp packet to 9.9.9.9 via wan1" \
    disabled=yes dst-address=9.9.9.9 out-interface=ether1_WAN1 protocol=icmp
add action=drop chain=output comment="deny icmp packet to 8.8.8.8.via wan3" \
    disabled=yes dst-address=8.8.8.8 out-interface=ether3_WAN3 protocol=icmp
add action=drop chain=output comment="deny icmp packet to 8.8.8.8 via wan2" \
    disabled=yes dst-address=8.8.8.8 out-interface=ether2_WAN2 protocol=icmp
add action=drop chain=output comment="deny icmp packet to 8.8.4.4 via wan2" \
    disabled=yes dst-address=8.8.4.4 out-interface=ether2_WAN2 protocol=icmp
add action=drop chain=output comment="deny icmp packet to 9.9.9.9 via wan3" \
    disabled=yes dst-address=9.9.9.9 out-interface=ether3_WAN3 protocol=icmp
add action=drop chain=input comment="Drop TCP on port 53" dst-port=53 \
    in-interface-list=WAN protocol=tcp
add action=drop chain=input comment="Drop UDP on port 53" dst-port=53 \
    in-interface-list=WAN protocol=udp
/ip firewall mangle
add action=accept chain=prerouting comment="accept rule" dst-address=\
    223.239.128.0/24
add action=accept chain=prerouting dst-address=49.205.176.0/24
add action=accept chain=prerouting dst-address=192.168.29.0/24
add action=accept chain=prerouting dst-address=192.168.1.1
add action=mark-connection chain=prerouting comment="mark connection rule" \
    connection-mark=no-mark connection-state=new in-interface=ether1_WAN1 \
    new-connection-mark=WAN1_Conn passthrough=yes
add action=mark-connection chain=prerouting connection-mark=no-mark \
    connection-state=new in-interface=ether2_WAN2 new-connection-mark=\
    WAN2_Conn passthrough=yes
add action=mark-connection chain=prerouting connection-mark=no-mark \
    connection-state=new in-interface=ether3_WAN3 new-connection-mark=\
    WAN3_Conn passthrough=yes
add action=mark-connection chain=prerouting comment="PCC Rule ACT Fiber" \
    connection-mark=no-mark connection-state=new dst-address-type=!local \
    in-interface=bridge1 new-connection-mark=WAN2_Conn passthrough=yes \
    per-connection-classifier=src-address-and-port:5/2
add action=mark-connection chain=prerouting connection-mark=no-mark \
    connection-state=new dst-address-type=!local in-interface=bridge1 \
    new-connection-mark=WAN2_Conn passthrough=yes per-connection-classifier=\
    src-address-and-port:5/3
add action=mark-connection chain=prerouting comment="PCC Rule Airtel" \
    connection-mark=no-mark connection-state=new dst-address-type=!local \
    in-interface=bridge1 new-connection-mark=WAN1_Conn passthrough=yes \
    per-connection-classifier=src-address-and-port:5/0
add action=mark-connection chain=prerouting connection-mark=no-mark \
    connection-state=new dst-address-type=!local in-interface=bridge1 \
    new-connection-mark=WAN1_Conn passthrough=yes per-connection-classifier=\
    src-address-and-port:5/1
add action=mark-connection chain=prerouting comment="PCC Rule Jio Fiber" \
    connection-mark=no-mark connection-state=new dst-address-type=!local \
    in-interface=bridge1 new-connection-mark=WAN3_Conn passthrough=yes \
    per-connection-classifier=src-address-and-port:5/4
add action=mark-routing chain=prerouting comment="mark routes" \
    connection-mark=WAN1_Conn in-interface=bridge1 new-routing-mark=to_WAN1 \
    passthrough=yes
add action=mark-routing chain=prerouting connection-mark=WAN2_Conn \
    in-interface=bridge1 new-routing-mark=to_WAN2 passthrough=yes
add action=mark-routing chain=prerouting connection-mark=WAN3_Conn \
    in-interface=bridge1 new-routing-mark=to_WAN3 passthrough=yes
add action=mark-routing chain=output comment="output rule" connection-mark=\
    WAN1_Conn new-routing-mark=to_WAN1 passthrough=yes
add action=mark-routing chain=output connection-mark=WAN2_Conn \
    new-routing-mark=to_WAN2 passthrough=yes
add action=mark-routing chain=output connection-mark=WAN3_Conn \
    new-routing-mark=to_WAN3 passthrough=yes
add action=mark-connection chain=postrouting comment="NAT Ping Failover" \
    connection-state=new new-connection-mark=WAN1_Conn out-interface=\
    ether1_WAN1 passthrough=yes
add action=mark-connection chain=postrouting connection-state=new \
    new-connection-mark=WAN2_Conn out-interface=ether2_WAN2 passthrough=yes
add action=mark-connection chain=postrouting connection-state=new \
    new-connection-mark=WAN3_Conn out-interface=ether3_WAN3 passthrough=yes
/ip firewall nat
add action=masquerade chain=srcnat src-address=192.168.1.0/24
add action=masquerade chain=srcnat out-interface=ether2_WAN2
add action=masquerade chain=srcnat out-interface=ether3_WAN3
add action=redirect chain=dstnat comment="Drop Port53 TCP" dst-port=53 \
    in-interface-list=WAN protocol=tcp
add action=redirect chain=dstnat comment="Drop Port53 UDP" dst-port=53 \
    in-interface-list=WAN protocol=udp
/ip route
add check-gateway=ping comment=pcc-Airtel distance=1 gateway=223.239.128.1 \
    routing-mark=to_WAN1
add check-gateway=ping comment=pcc-ACT disabled=yes distance=1 gateway=\
    49.205.176.1 routing-mark=to_WAN2
add check-gateway=ping comment=pcc-Jio distance=1 gateway=192.168.29.1 \
    routing-mark=to_WAN3
add distance=1 gateway=223.239.128.1
add distance=2 gateway=192.168.29.1
add comment=default-failover disabled=yes distance=10 gateway=49.205.176.1
add comment=netwatch-jio distance=1 dst-address=8.8.4.4/32 gateway=\
    192.168.29.1
add comment=netwatch-airtel distance=1 dst-address=8.8.8.8/32 gateway=\
    223.239.128.1
add comment=netwatch-act distance=1 dst-address=9.9.9.9/32 gateway=\
    49.205.176.1
/ip service
set telnet disabled=yes
set ftp disabled=yes
set www address=192.168.1.0/24 disabled=yes
set ssh disabled=yes
set api disabled=yes
set winbox address=192.168.1.0/24
set api-ssl disabled=yes
/ip upnp
set enabled=yes
/ip upnp interfaces
add interface=bridge1 type=internal
add forced-ip=223.239.128.14 interface=ether1_WAN1 type=external
add disabled=yes interface=ether2_WAN2 type=external
add interface=ether5 type=internal
add interface=ether3_WAN3 type=external
/system clock
set time-zone-name=Asia/Kolkata
/system logging
add disabled=yes topics=dns
/tool netwatch
add comment=AirTel_WAN1_conn down-script="ip route disable [find dst-address=0\
    .0.0.0/0  gateway=223.239.128.1]\
    \n:log error \"Airtel Link down\"\
    \n/ip firewall connection remove [find]" host=8.8.8.8 interval=5s \
    timeout=400ms up-script="ip route enable [find dst-address=0.0.0.0/0 gatew\
    ay=223.239.128.1]\
    \nlog warning \"Airtel Link up\""
add comment=ACT_WAN2_conn down-script="ip route disable [find dst-address=0.0.\
    0.0/0 gateway=49.205.176.1] \
    \n:log error \"ACT is down\"\
    \n/ip firewall connection remove [find]" host=9.9.9.9 interval=5s \
    timeout=400ms up-script="ip route enable [find dst-address=0.0.0.0/0 gatew\
    ay=49.205.176.1]\
    \nlog warning \"ACT is up\""
add comment=Jio_WAN3_conn down-script="ip route disable [find dst-address=0.0.\
    0.0/0 gateway=192.168.29.1] \
    \n:log error \"Jio Link down\"\
    \n/ip firewall connection remove [find]" host=8.8.4.4 interval=5s \
    timeout=400ms up-script="ip route enable [find dst-address=0.0.0.0/0 gatew\
    ay=192.168.29.1]\
    \nlog warning \"Jio Link up\""

jaclaz · November 2, 2025, 3:19pm

Or maybe the timeout set at 400 ms is just too low.

But you are also using check-gateway=ping.

Generally speaking the result of too "aggressive" connectivity checking is flapping.

As an experiment, try increasing the timeout, at least for ISP1 and see if things change.

tushar · November 2, 2025, 3:39pm

i did same thing even disabled NETWATCH to isolate to check.