ROUTER + STATIC IP's = BAD BEDFELLOWS

[BatmanNate]

Okay, this has just flat out stumped me. Usually if I toy with it long enough, it ends up working, but this time it just keeps getting more and more fubar... Here is the situation: I have a dual ISDN internet connection which I access through a router, currently the router is the DHCP server and and uses NAT to route all the computers on my network through a single IP. I have leased a block of 8 static IP's recently, and I cannot for the life of me figure out how to set them up. The IP block looks something like this:

IP #1: "Network Identifier"
IP #2-#6: User assignable
IP #7: Reserved for routing (NAT uses this IP)
IP #8: Reserved for broadcasts

Now, I understand that for static I need to assign one of the user assignable iP's to the TCP/IP stacks on my desktops, however what I'm confused about is what IP should I assign the router itself? Should it be an internal IP or one from the block? Also, should I assign it the subnet mask for the static block, or a seperate one? According to the router documentation, I am supposed to use whatever IP I assign the router as the default gateway/DNS address in the TCP/IP stacks on my desktops as well. Now, there is also a default gateway address and default DNS address from the ISP, I assume that I assign these in the router. I've tried many different combinations to try and make this work...I've set it up as described above with DHCP on/off, NAT on/off, the whole works, and it ends up either the router can't connect to the ISP or I can't talk to the router and I have to reset the whole damn thing. Any ideas guys? 3com's documentation is very sub-par in the area of configuring statics, and Qwest just plain sucks. Anyway, the router is a 3com Officeconnect, and I have reserved the IP's that I want for statics on the router as well, that's not the problem. Help away!!!

By the way, does anyone know what the "network identifier" IP is for??

-Nate

 

[ScottMac]

When you say "dual ISDN" connection, are you taking about a BRI (2B+d) or two BRI, or two PRI (like a T1)?

Scott

 

[spidey07]

IP #1: "Network Identifier"
IP #2-#6: User assignable
IP #7: Reserved for routing (NAT uses this IP)
IP #8: Reserved for broadcasts

IP #1 is the network number and can never be used
IP #2-6 are free for you to assign to end stations
IP #7 is probably the LAN interface on the router and is used for NAT
IP #8, well that's a broadcast.

Lemee guess, your subnet mask is 255.255.255.248? the ISDN interfaces on the router are probably using IP unnumbered and have no address.

 

[DnetMHZ]

should only need to assign ip's 2-6 to the end stations and turn off NAT on the router

 

[Russ]

You can use ANY of the user assignable addresses with the router. In my case, I just used the first available of those. My setup is similar, except it's DSL with the Cisco 675. My block is:

207.108.218.136 Network identifier.
207.108.218.137 User assignable.
207.108.218.138 User assignable.
207.108.218.139 User assignable.
207.108.218.140 User assignable.
207.108.218.141 User assignable.
207.108.218.142 Routing.
207.108.218.143 Broadcasts

Spidey is correct that the mask is 255.255.255.248.

I assigned 207.108.218.137 to the Linksys router, and 207.108.218.142 is assigned to the Cisco. I have NAT and DHCP ENABLED on the router, and DISABLED on the Cisco.

I don't know if an ISDN device uses an IP address. If it doesn't, then you might need to assign the routing address to the router. Of course, that would mean that you get to use all five of the user assignable for systems.

The Cisco runs to a switch, which runs to the router. Then an additional cable runs from the switch as a direct pipe to my server in order to use the other four assignable IP addresses. The internal systems are DHCP off the router.

Now, I don't know if your ISDN device is doing NAT, but if so, disable that feature. Also, if you want to assign the additional WAN addresses to systems, you're either going to have to disable NAT on your router, or setup a bypass like I have.

In the last case (assigning the IP addresses to systems), you've essentially eliminated the need for the router and could simply use a switch.

Russ, NCNE

 

[BatmanNate]

Thanks for all the replies guys, however I'm still slightly confused. I'm using the router because it is also my ISDN modem (it's a 3com office connect LAN modem/router/hub) so it is my connection to the internet. The subnet is 255.255.255.248, yes. So you you saying that if I assign the 3com one of the assignable IP's, and then assign my systems the other assignable IP's, and turn off NAT, then all should be well? It tried it before and it didn't work... about the gateways, should I make the IP of the router the default gateway of my systems? Thanks again guys!

 

[Damaged]

You can't always use any of the IPs in a range given to you to assign to the router, particularly in a dial up situation. For example, we use RADIUS to assign that information to customers ( Framed-IP-Address = <some IP number> Framed-IP-Netmask = <some netmask> ). You assign something other than what we've assigned and it no worky. As this user notes whilst messing around with different settings &quot;either the router can't connect to the ISP...&quot; See, no worky.

However. Yes, if you turn off NAT, then you assign the IP address of your router as the default gateway to each of your machines.

What are you doing to test connectivity? Have you tried just pinging by ip number?

Last but not least, you don't have some sort of proxy or firewall in the way do you? Just a thought. And these machines are connected to some hub/switch that connects to the office connect and there's good link there? I usually play with these things with a laptop connected directly into the device. If that works, then I know that it's something in my local segment...somewhere.

 

[BatmanNate]

Ah, problem sovled guys. I used IP #7 (the reserved for routing IP) and used it as the IP of the router itself, assigned everythign else thier statics, reserved them under the DHCP controller, and disabled NAT. It's worky worky. Thanks all!