Page 1 of 1

Dynamic IP Address from ISP

Posted: Mon Nov 24, 2014 12:22 am
by lyberis1979
Dear all,

Im new to the world of router boards my first one is a CRS125-24G-1S-2HnD-IN Cloud Router Switch. So bear with me in this one, i have a ZTE Router and i have set it in bridge mode // no dhcp etc. In the mikrotik i have plug it in the poe 1st port and in the quick settings panel i have set it in POE, i have declared there my creds from my ISP and connected. The following pic shows the IP that I'm getting from my mikrotik and next one is from the whats my ip??? Any suggestions on this.


My bests to you all :)

Re: Dynamic IP Address from ISP

Posted: Mon Nov 24, 2014 4:28 pm
by v12
That's easy - you're behind your ISP's NAT.

Re: Dynamic IP Address from ISP

Posted: Tue Nov 25, 2014 8:50 am
by 43north
Hmmm this is interesting and I am not sure but curious if someone else chimes in. My thought is that your modem is not truely in bridge mode since you are pulling a 10. private subnet for your WAN? Could be totally fine depending on how your ISP is doing their address hand outs.

Re: Dynamic IP Address from ISP

Posted: Wed Nov 26, 2014 10:06 am
by lyberis1979
Hmmm this is interesting and I am not sure but curious if someone else chimes in. My thought is that your modem is not truely in bridge mode since you are pulling a 10. private subnet for your WAN? Could be totally fine depending on how your ISP is doing their address hand outs.

Good morning,

Have a nice day to you all, i have tried it with a CRS109-8G-1S-2HnD-IN borrowed from a friend, dint change the settings just plug it in, and reads the ip address, in my own goes with the above. Also with a CISCO rv180

Re: Dynamic IP Address from ISP

Posted: Wed Nov 26, 2014 10:12 am
by lyberis1979
That's easy - you're behind your ISP's NAT.

Good morning,

How that possible!!!!! When you are having the same terminal for processing the IP address!!! Its not like it dial two times!!! That would be great ;).

Being behind a NAT as my experience says you get only only one IP routed in a different Network , now from this example i get 2 IP addresses and they both WORK from this modem!!!

WEIRD....

Re: Dynamic IP Address from ISP

Posted: Thu Nov 27, 2014 7:21 pm
by jfvelamoscoso
This is the same that some ISP are doing on my country.

The ISP is giving you the private ip 10.x.x.x/8 this is set up on their servers. On some router their nating several clients to the same public ip in order to not use to many ip. I know it is ugly but this is how they are doing. You only have one IP which is the private one, but when you will go out to internet (Maybe outside your AS) you will be nat by the isp

Re: Dynamic IP Address from ISP

Posted: Fri Nov 28, 2014 11:59 am
by lyberis1979
This is the same that some ISP are doing on my country.

The ISP is giving you the private ip 10.x.x.x/8 this is set up on their servers. On some router their nating several clients to the same public ip in order to not use to many ip. I know it is ugly but this is how they are doing. You only have one IP which is the private one, but when you will go out to internet (Maybe outside your AS) you will be nat by the isp

Thats preventing me from using any DDNS services, or theres any way around this. Or even in the scenario that I'm going to use a pool of static addresses ???

Re: Dynamic IP Address from ISP

Posted: Fri Nov 28, 2014 4:05 pm
by jfvelamoscoso
Yes it will private to use DDNS because your server or device doesn't use any public ip, this ip is shared by a lot of people. If they ISP can give you and Public IP Pool you can solve this issue, just in case you need public ones. Otherwise they are using 10.x.x.x/8 if you use any 192.168.x.x/16 you will not have problem with this. What is your target?

Re: Dynamic IP Address from ISP

Posted: Fri Nov 28, 2014 4:27 pm
by lyberis1979
Yes it will private to use DDNS because your server or device doesn't use any public ip, this ip is shared by a lot of people. If they ISP can give you and Public IP Pool you can solve this issue, just in case you need public ones. Otherwise they are using 10.x.x.x/8 if you use any 192.168.x.x/16 you will not have problem with this. What is your target?

Fair question,

Im looking to use the DDNS service as an access to the router from all means as possible, vpn, telnet etc. Far from that i came across an issue with my Fortigate, can't resolve the DNS from the router and can't connect to the fortinate dans to activate my license!!! The thing also is that when I'm connecting the fortunate directly to the modem I'm getting the dIP correctly. The only issue with the mikrotik.


the home network is at 192.168.x.x/20.


Best regards.

Re: Dynamic IP Address from ISP

Posted: Fri Nov 28, 2014 4:36 pm
by jfvelamoscoso
Think that you will not be able to connect the mikrotik outside your office if you have a private ip, maybe if you ask the isp to give you an port fowarding. But not sure if they would like. About fortinet really don't know about it, but some devices show they public ip no matter you have an private ip, show both ip. As it is dinamic and both connected directly to the modem, both should receive the same ip.

Re: Dynamic IP Address from ISP

Posted: Fri Nov 28, 2014 5:19 pm
by lyberis1979
Think that you will not be able to connect the mikrotik outside your office if you have a private ip, maybe if you ask the isp to give you an port fowarding. But not sure if they would like. About fortinet really don't know about it, but some devices show they public ip no matter you have an private ip, show both ip. As it is dinamic and both connected directly to the modem, both should receive the same ip.

Haven't seen this before anywhere in Greece, but first time for everything... right!! The thing is i don't understand why is the Fortigate is giving me the REAL ip and the mikrotik don't !!! The WEIRD thing is like I'm having two dynamic IP's at the same time, the modem "ZTE wind blabla something" has the 37.130.2.45 example and its visible from any whats my ip site!! and when I'm trying to connect from the mikrotiks ip 10.10.10.10 something is only accessible from my internal network. Both of the ip's are coming from different gateways from my ISP. The 37.34.24.12 with is from my wind router zte was a gateway 62.254.14.56 wich is a valid one "I'm working with this sip for over 10 years now".

I will post some photos later on to see my point.

Re: Dynamic IP Address from ISP

Posted: Tue Dec 02, 2014 9:32 am
by lyberis1979
This is the same that some ISP are doing on my country.

The ISP is giving you the private ip 10.x.x.x/8 this is set up on their servers. On some router their nating several clients to the same public ip in order to not use to many ip. I know it is ugly but this is how they are doing. You only have one IP which is the private one, but when you will go out to internet (Maybe outside your AS) you will be nat by the isp

Good Morning Mate,

Confirmed, I'm behind NAT.

Re: Dynamic IP Address from ISP

Posted: Tue Dec 02, 2014 6:01 pm
by jfvelamoscoso
Nice, Well not nice, but is good that you find the reason. They apply the same policy on my country (PerĂº) some time ago but oonly on residencial services

Re: Dynamic IP Address from ISP

Posted: Tue Dec 02, 2014 6:50 pm
by lyberis1979
Nice, Well not nice, but is good that you find the reason. They apply the same policy on my country (PerĂº) some time ago but oonly on residencial services

Can you believe that this would be solved if i get a static IP??