Hi! My home network uses D-Link Router providing 192.168.1.x addrress throughout our home network. When I connect Cisco 831 Router so that I can be be part of our office VPN network, My D-Link address scheme changes to 10.10.x.x. I'm not sure why it is doing that.
My Cisco 831 router is sitting behind D-Link router. The following may illustarte the setup:
Cable Modem----DHCP------->WAN Port on D-Link--------->One of the LAN Ports-------192.168.1.x----->Cisco Router
The Cisco Router does see the 192.168.1.x adress provided by D-Link.
However, when I disconnect Cisco Router LAN Cable from the D-Link router, I am back to 192.168.1.x address throught my home network and obviously everything works fine.
Can one explain the possible cause of this and what should I set/check to solve this issue. yaj
Sounds to me like your Cisco router is setup for dhcp and is giving out IP addresses to your dlink clients before your dlink can respond. At its most basic level, the dlink is a switch, and just had a dhcp server built into its software. When a client sends a dhcp request, the dlink will forward that request out all LAN ports as it is a simple broadcast. Since there are usually no other dhcp servers, the dlink's dhcp server request is used and gives out a 192.168.x.x. But, and this is not uncommon, the Cisco router is probably receiving the request and is configured to give out a 10.x. network range address via its own dhcp configuration. You need to look at your cisco config......why not just use the cisco router as both your gateway and vpn termination? I'm sure your office is using private IP addressing anyway, so its not like client traffic will mistakenly go there...and if your office is allowing vpns in this scenario, obviously they aren't that security conscious.
Interestingly you touch the exact points that I thought seemed to be happening.
Understood! Cisco and D-Link having inherent router specific functionality, will generate an IP Address in the range specfied. i.e. 192,168.1.x and
10.10.10.x respectively.
What I think is happening, Ciscco is passing that IP to D-Link and sometimes D-Link turns around and overrides its own generated IP (192.168.1.x) and passes along 10.10.10.x address within Home Network. Seems like a voodoNetwork setup.
Having learnt this, it also means if Cisco Router traffic is channeled through D-Link Gateway address 192,168.1.1. Is this a correct statement?
Tell me! Does htis mean, that home network is exposed to Cisco router while on VPN through Cisco connection?
I think to solve this entire issue it would be ebst to subscribe to 2 seperate IP addresses and segment two networks using NetGear Hub. Network A will service 192.68.1.x while Network B will service 10.10.10.x devices.
Well, you are confusing layer 2 and layer 3 a bit. IPs are at layer 3 and are routed, and switches are at layer 2. Your DLINK router is both a layer 3 router and a layer 2 switch. The 4 ports on the back of it (or however many you have) are switch ports. When a node broadcasts for an IP address, it goes into the dlink switch, and the dlink software router hears that request and gives the client a
192.168.x.x address. However, the nature of switches is that broadcasts are forwarded out all switch ports since it is a broadcast. If you have another dhcp server or router that is plugged into a switchport in the same network, that device will also hear the request and try to service it. At that point, it comes down to which device is faster in servicing the request, in which case it sounds like the Cisco is responding first and thus providing a 10.10.10.x ip address first.
That being said, I'm not sure what you are trying to do here. If you are desiring to have a permanent VPN tunnel between the Cisco router and your office, and have clients behind that router have direct access to your work network, then you need to turn off DHCP on the interface that goes to DLINK, and turn on DHCP on the internal side of the router. However then we get complicated as you would need static routes on the dlink to tell it how to get to the new network behind the Cisco.
I think your best bet is to stop using the DLINK as a router and rely on your Cisco. To do this, plug your internet connection into your Cisco ethernet port and configure as needed (turn off dhcp), turn on DHCP on another internal ethernet interface, and run a cable between that interface and one of the DLINK's switchports. You will no longer be using the dlink's WAN port, and you want to disable dhcp on the dlink altogether. At this point you will be using the Cisco router as your router, and the dlink as just a switch (if you disable DHCP on the dlink and do not use the WAN/Internet Port, it is essentially a switch only).
Personally, this is not complicated but you may want to find some local help by someone who has experience. Based on your questions, I'm unsure of your experience level, and I'd hate to have you start down this path only to realize that its not working and you don't understand why or what to fix.
I believe I understand exactly what you are saying and certainly comprehend the recommendations you make. Certainly as I thought before, between two DHCP srevrs running, one is contending with the other.
Obviously a dotted line picture could be worth a million words
I assume this means, I create static routes within D-Link for Home Network and use Cisco default gateway to getb out on the Internet.
Yes, that is correct. Although if you use the second scenario and cutoff the DLINK router part, you would not need that as the cisco will be your only layer 3 device.
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