Question Router LAN IP vs Modem LAN IP ?

Oct 13, 2022
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I'm trying to set up my LAN IP to be in the 192.168.5.0/24 range while my Centurylink modem (ZyXEL 2100Z) LAN IP is 192.168.0.1.

The reason is for an added security layer, maybe there is a better way?

I have a Linksys WRT 32X behind the modem and another router, the ASUS RT N16 connected by ethernet in the garage.

I can't get the modem to recognize the Linksys router either in bridged mode or not.
I had this working with two Linksys WRT 54g routers in the past.
It feels like I'm missing something simple.
Am I barking up the wrong tree?

Thanks
 

Ralston18

Titan
Moderator
Not sure about the "big picture" with respect to your post.

Overall network connectivity generally matches the following line diagram ( where ---- > represents an Ethernet cable):

ISP === (Coax, DSL, Fiber) ===> Modem ----> [WAN Port] Router [LAN Ports] ----> wired devices and ~~~ wireless ~~~> wireless devices.

Sometimes the Modem and Router are combined.

Feel free to edit my line diagram to match your network environment.

Overall, only one device (Modem/Router or Router) should be enabled and configured to provide IP addresses to network devices.

All other Routers should have DHCP IP addressing disabled.

As understand your post you may be trying to create subnets that are separate and do not allow Subnet 1 devices to access Subnet 2 devices.

And vice versa - is that correct?

Feel free to edit and correct my line diagram as necessary to show your network environment and requirements.
 
I'm trying to set up my LAN IP to be in the 192.168.5.0/24 range while my Centurylink modem (ZyXEL 2100Z) LAN IP is 192.168.0.1.

The reason is for an added security layer, maybe there is a better way?

I have a Linksys WRT 32X behind the modem and another router, the ASUS RT N16 connected by ethernet in the garage.

I can't get the modem to recognize the Linksys router either in bridged mode or not.
I had this working with two Linksys WRT 54g routers in the past.
It feels like I'm missing something simple.
Am I barking up the wrong tree?

Thanks
This has no bearing on security as far as I can see?
 
Oct 13, 2022
5
0
10
0
Not sure about the "big picture" with respect to your post.

Overall network connectivity generally matches the following line diagram ( where ---- > represents an Ethernet cable):

ISP === (Coax, DSL, Fiber) ===> Modem ----> [WAN Port] Router [LAN Ports] ----> wired devices and ~~~ wireless ~~~> wireless devices.

Sometimes the Modem and Router are combined.

Feel free to edit my line diagram to match your network environment.

Overall, only one device (Modem/Router or Router) should be enabled and configured to provide IP addresses to network devices.

All other Routers should have DHCP IP addressing disabled.

As understand your post you may be trying to create subnets that are separate and do not allow Subnet 1 devices to access Subnet 2 devices.

And vice versa - is that correct?

Feel free to edit and correct my line diagram as necessary to show your network environment and requirements.
It's a DSL connection and DHCP on the modem is disabled so the router behind it will assign IP addresses.

With that router set as 192.168.5.0 it gets no signal from the modem.
I realize the second router won't be assigning addresses.

All devices in the LAN should have 192.168.5.0/24 as the IP but each device can see the others.

The problem is the modem does not recognize the router or the router can't see the modem, not sure. In any case the router cannot connect to the internet.
 

Ralston18

Titan
Moderator
192.168.0.1 and 192.168.5.0

What subnet mask or masks are you using or trying to use?

If I understand the current IP addresses correctly the 192.168.5.0 should not be in use.

Or will require a subnet mask of 255.255.0.0

Please provide a line diagram showing the modem, all of the routers, and the IP address and respective subnet masks being used.

Or a network sketch that you can scan in and post here via imgur (www.imgur.com).

Indicate which router is the DHCP router.

Again, by "adding security" is your intent to have separate subnets?

Each with access to the internet but not to each other?
 
As mentioned above you are going to have to show how you have this cabled and where you think IP are assigned.

In general you can not just disable the DHCP server on a router and have another "consumer" grade router do the DHCP function. The DHCP ability in consumer router generally can not assign the gateway IP to point to another device.

If you mean you are running the DSL router in bridge mode then it gets messy. DSL many times require some kind of special settings on the WAN port of the replacement router. In general this is PPPoE but it may require certain setting that you should either look up on your ISP site or call and talk to them about how you do this.
 

palladin9479

Distinguished
Moderator
It's a DSL connection and DHCP on the modem is disabled so the router behind it will assign IP addresses.

With that router set as 192.168.5.0 it gets no signal from the modem.
I realize the second router won't be assigning addresses.

All devices in the LAN should have 192.168.5.0/24 as the IP but each device can see the others.

The problem is the modem does not recognize the router or the router can't see the modem, not sure. In any case the router cannot connect to the internet.
Ok where are you setting the IP for the Router?

Routers route IP traffic between interfaces, in this case one interface (WAN) is connected to the modem and should be getting an DHCP IP from the ISP, while the other interface (LAN) is connected to the internal switch and services your local network. The LAN interfaces are typically set to 192.168.1.0/24 and provide local DHCP services.

It's sounding like you want to change the LAN subnet from 192.168.1.0/24 to 192.168.5.0/24, which you can do as long as you find the spot where it's set and just change the 1 to a 5. Absolutely do not attempt to put a static IP on the WAN interface, the router will be unable to communicate with the ISP if you do that.
 
Oct 13, 2022
5
0
10
0
192.168.0.1 and 192.168.5.0

What subnet mask or masks are you using or trying to use?

If I understand the current IP addresses correctly the 192.168.5.0 should not be in use.

Or will require a subnet mask of 255.255.0.0

Please provide a line diagram showing the modem, all of the routers, and the IP address and respective subnet masks being used.

Or a network sketch that you can scan in and post here via imgur (www.imgur.com).

Indicate which router is the DHCP router.

Again, by "adding security" is your intent to have separate subnets?

Each with access to the internet but not to each other?
192.168.0.1 and 192.168.5.0

What subnet mask or masks are you using or trying to use?

If I understand the current IP addresses correctly the 192.168.5.0 should not be in use.

Or will require a subnet mask of 255.255.0.0

Please provide a line diagram showing the modem, all of the routers, and the IP address and respective subnet masks being used.

Or a network sketch that you can scan in and post here via imgur (www.imgur.com).

Indicate which router is the DHCP router.

Again, by "adding security" is your intent to have separate subnets?

Each with access to the internet but not to each other?
Thanks for the reply.
Sorry it has taken so long to reply, unexpected medical tests and procedures have kept me away.

Edit: Just realized I didn't respond to your question about my intention regarding subnets.
My intention and what I'd read (Thinkgeek IIRC) was that changing your LAN to, for instance 192.168.5.0 and rejecting random pings made my boxes appear to not exist. So I guess(?) that would be a subnetb IIRC,
Here's the layout. ---> denotes ethernet

Formatting was mangled after posting.
So, the linksys router is connected to the unmanaged switch via ethernet which feeds the ASUS also by ethernet.

Both NAS are boxes connected to the switch which also connects, via ethernet, to the ASUS router which feed the two computers and various wireless devices in the garage.

modem LAN port--->Linksys router LAN port--->unmanaged switch --> Asus router LAN port---->computer 1
" --------->NAS #1 "--------> computer two
"--------> NAS #2 " ------>various wireless devices
Both routers use 255.255.255.0 as subnet mask - havent tried anything different yet.

As I said I've disabled DHCP on the ph. co's modem and it is enabled on the Linksys router.
DHCP is also disabled on the ASUS router which I guess only functions as a switch and wireless AP now.

Devices need not be able to communicate except for the two computers connected to the ASUS unit.

My understanding is that LAN IP on my devices being different from the phone company's default helps to insulate my LAN from outside intrusion/detection.

Maybe I'm misinformed and the 192.168.0.1/24 for all devices in the house is just as secure.
 
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