I hope there are english speaking users around, as I don't speak russian
So, a few months ago we changed from 20/1 mbit DSL to 100/50 mbit Optical internet and all the problems started. First I had no idea what the problem is, but devices were keep reporting ip conflicts on the local network. After further investigation I saw that the routers dhcp server has two options set, DHCP Start IP and DHCP End IP, which had the following options
Start IP Address: 192.168.1.2
End IP Address: 192.168.1.14
Since I have over 10 wireless devices around my house + desktop computers, android phones, smart devices, 13 IPs are simply not enough for me. No matter how hard I tried to change the value to be higher then .14, a javascript alert kept saying "IP Address 192.168.1.20 is invalid IP address.".
Basically, if the number is above 14, it keeps saying that. Also there was something else I found weird about the options, and that was the subnet mask, which was set to 255.255.255.240. I always used 255.255.255.0 before, but I didn't really pay any attention to this since now. After investigating this subnet mask, I came along this url,
https://dnsmadeeasy.com/support/subnet/
which states that on this subnet mask, you are not able to use more then the preset ips. You can use less, but once the last digit of the end IP is higher then 14, well, it accepts 15 as well, it simply won't save. I can override this javascript error by tampering the form, and setting higher values to the router by hand using
http://192.168.1.1/lancgiuser.cmd?ethIpAddress=192.168.1.1ðSubnetMask=255.255.255.240&dhcpEthStart=192.168.1.2&dhcpEthEnd=192.168.1.254&dhcpLeasedTime=24&enblDhcpSrv=1ðIpAddressingType=Static&sessionKey=1223317128
which will actually work, but after reloading the page, the values are back to .14, as that's the highest possible value to the current subnet mask. Which is ok, I guess...
So, I tried to change the subnet mask to 255.255.255.0, saved the settings, changed the end ip to 192.168.1.254, and guess what, the form processed, the values were saved and every device got it's own, unique ip.
I forgot to mention, if the subnet mask is set to 255.255.255.240, and I try to access one of my IP cameras for example, which has a static IP of 192.168.1.30, I can not access it. Basically, I can't see, ping or access anything that is on a higher IP then .14. - I guess this is normal if the subnet mask .240 is set.
So, the current state is the following:
Subnet mask is set to be: 255.255.255.0
Start IP: 192.168.1.2
End IP: 192.168.1.254
And everything works as expected, but...
after some time, I can't really tell if it's minutes or hours, I can't really figure out how many minutes pass, the IP conflict appears again. I log back in to the router and guess what.. the subnet mask is back to 255.255.255.240 and the end ip is back to 192.168.1.14. No one touched anything, no one access the router from inside the network, but the values are back to their original state.
It's an Eltex NTU-RG-1421G-Wac:rev.A1 router, which comes with it's default user/password for the admin interface, which is
username: user
password: user
however, my isp changed the password to be it's own name, so let's say, it's "myisp" atm, so
username: user
password: myisp
Not a big deal, I would say, most of the isps do this, well in my country.
I thought, maybe someone from the isp, an automated script, or something keeps accessing the router somehow and changing back the values automatically, so I tried to change the password to be something random and unique.
So, the password was changed, the subnet mask is changed back to 255.255.255.0 and the End ip changed to 192.168.1.254, saved everything and let the time pass.
Some time later, again, I can't really figure out if it's minutes or hours, the IP conflict appeared again. I tried to access my router using the newly changed, unique password set by me the last time I changed settings, and I received an Invalid Username or Password error. Tried the original user/password provided by my ISP (user/myisp) and it worked. I'm in, and guess what, the subnet mask is back to 255.255.255.240, the End IP is back to 192.168.1.14.
I tried to change some other stuff inside the router such as the internet time servers, that stay untouched all the time. How I see, only the Subnet mask, Dhcp End IP and the password are changed from time to time.
So, here's what I did now. Enabled logging in the router. Set all log values to be "INFORMATIONAL", set everything back to my own settings, and waited. Here's what happened
After 1 hour of waiting, reloading the LAN settings every minute, to see when it's changing, checking the logs every minute, I just realized the reset happens after about 1 hour. Here's the complete log provided by the router (i changed my ip in the log to be "MY-IP-ADDRESS", but it's showing my public ip address in the original log)
Management / System Log / View
Date/Time Facility Severity Message
Jan 1 01:04:05 syslog emerg ######################################
Jan 1 01:04:05 syslog emerg ## syslogd started: BusyBox v1.17.2 ##
Jan 1 01:04:32 daemon err radvd[1741]: no linklocal address configured for br1
Jan 1 01:04:32 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 01:04:32 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:04:48 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 01:04:48 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:04:53 daemon err radvd[1741]: no linklocal address configured for br1
Jan 1 01:04:53 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 01:04:53 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:04:54 kern alert kernel: Intrusion -> IN=veip0.1 OUT= MAC=e0:d9:e3:85:00:70:c8:1f:be:dd:a1:15:08:00:45:00:00:3c:c0:ba:40:00:39:06:85:c8:bc:24:2c:d1:55:de:bc:65:10:80:d0:44:36:10:90:fa:00:00:00:00 SRC=188.36.44.209 DST=MY-IP-ADDRESS LEN
Jan 1 01:05:09 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:05:25 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 01:05:25 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:05:41 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 01:05:41 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:09:43 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 01:09:43 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:14:20 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 01:14:20 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:15:07 kern alert kernel: Intrusion -> IN=veip0.1 OUT= MAC=e0:d9:e3:85:00:70:c8:1f:be:dd:a1:15:08:00:45:00:00:28:a1:55:40:00:f4:06:22:06:55:de:5b:52:55:de:bc:65:09:24:00:17:d4:ca:52:91:00:00:00:00 SRC=85.222.91.82 DST=MY-IP-ADDRESS LEN=
Jan 1 01:19:04 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:23:37 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 01:23:37 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:25:30 kern alert kernel: Intrusion -> IN=veip0.1 OUT= MAC=e0:d9:e3:85:00:70:c8:1f:be:dd:a1:15:08:00:45:00:00:3c:0a:82:40:00:3a:06:93:25:58:97:38:3a:55:de:bc:65:b3:92:7f:bf:a9:8d:e8:43:00:00:00:00 SRC=88.151.56.58 DST=MY-IP-ADDRESS LEN=
Jan 1 01:30:17 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:34:46 kern alert kernel: Intrusion -> IN=veip0.1 OUT= MAC=e0:d9:e3:85:00:70:c8:1f:be:dd:a1:15:08:00:45:00:00:3c:3b:1e:40:00:36:06:84:83:d5:de:9c:f8:55:de:bc:65:11:05:cf:95:f1:4d:3c:da:00:00:00:00 SRC=213.222.156.248 DST=MY-IP-ADDRESS L
Jan 1 01:37:58 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:44:53 kern alert kernel: Intrusion -> IN=veip0.1 OUT= MAC=e0:d9:e3:85:00:70:c8:1f:be:dd:a1:15:08:00:45:28:00:28:6b:5a:40:00:f4:06:fc:5a:25:31:e7:7d:55:de:bc:65:2f:fd:15:b3:00:00:7a:75:00:00:00:00 SRC=37.49.231.125 DST=MY-IP-ADDRESS LEN
Jan 1 01:47:45 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:52:36 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 01:52:36 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 01:54:50 kern alert kernel: Intrusion -> IN=veip0.1 OUT= MAC=e0:d9:e3:85:00:70:c8:1f:be:dd:a1:15:08:00:45:00:00:2c:c8:96:00:00:36:06:af:fb:1f:a8:da:4e:55:de:bc:65:eb:5e:00:17:55:de:bc:65:00:00:00:00 SRC=31.168.218.78 DST=MY-IP-ADDRESS LEN
Jan 1 02:01:44 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 02:01:48 kern warn kernel: backup_psi_number_blk=1 result=24576
Jan 1 02:01:59 daemon err radvd[1741]: no linklocal address configured for br1
Jan 1 02:01:59 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 02:01:59 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 02:02:15 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 02:02:15 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 02:02:30 daemon err radvd[1741]: no linklocal address configured for br1
Jan 1 02:02:30 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 02:02:30 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 02:02:46 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 02:02:46 daemon warn radvd[1741]: sendmsg: Network is unreachable
Jan 1 02:03:02 daemon warn radvd[1741]: resetting ipv6-allrouters membership on br1
Jan 1 02:03:02 daemon warn radvd[1741]: sendmsg: Network is unreachable
That's about it. I have no idea what's causing this, asked my ISP, they have no idea either. One other, IMPORTANT note. This is happening to EVERYONE using this ISP and this router. I don't have access to another router that is able to be connected to the optical line atm, so that's not really an option. This optical internet is fairly new in my city, so everyone is using the same eltex router.
Any help, suggestion, advice is appreciated!
Have a wonderful day,
Tamas