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DHCP option: Static Route Option

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6 replies

by edudley

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I have lan A and lan B connected by two routers over a frame relay. Users on lan A can ping thier router and my router but not anything on Lan A. I have set up seperate scopes for each lan with thier own IP addresses. I have been told that I needto setup the static route option in the DHCP. The static route option needs the destination/routers in pair in order or priority. When you open up static route option it just lets you add IP addresses. I need more information. Where can I go to get a full explanation or can someone explain.

6 replies

by stillatit

Start with the basics. If users on lan A cannot ping anything on lan A, you have a problem before you think about routers.

Looking at Lan A only for a moment, check that you have excluded the router and fixed server addresses from DHCP server's IP pool. Look at each PC (or a representative sample if you have a large lan), and make sure that all of the boxes on lan A actually have IP addresses and subnet masks for lan A. (Use winipcfg in Win95/98 or ipconfig in NT.)

Now do the same for lan B.

Take out any static routes you may have in DHCP.

Reboot the PC's you will test with.

At this point, at very least, every test box on lan A should be able to ping every other test box on lan A, including the inside (lan A) port of the router attached to lan A.

Now, for lan A, using the DHCP, give every station a default gateway address which is the inside port of the router touching lan A. Do the same for lan B. Reboot each PC so that the DHCP information will be reacquired.

If the routers are advertising their routes, you are done. A PC on Lan A, when addressing a lan B pc, will go to its default gateway, which is the router, the router will know the location of the lan B router because of RIP exchanges between the routers, and the router on lan B will be able to find the target pc. The ping return will follow the reverse path.

(see comment for continuation)

by stillatit

(continued)

If the routers are NOT using RIP, or if for some reason you need to have the default gateway pointed somewhere else, then you need the static route option. For lan A, the route is /. For lan B, the route is /.

Concrete example:
Your lan A net: 192.168.0.0 mask 255.255.255.0
Your lan A router: 192.168.0.1
Your lan B net: 192.168.1.0 mask 255.255.255.0
Your lan B router: 192.168.1.1

The object of static routing is to tell the computer that for a given network, this is the router where the packet should be sent. The router needs to have an address on the local subnet. Think of it as "If you are trying to send something here, give it to that guy, and he will know what to do with it."

Lan A static route is 192.168.1.0/192.168.0.1
Lan B static route is 192.168.0.0/192.168.1.1

If this works on your test boxes, reboot all PC's using DHCP so that they reacquire the information from the DHCP server.

If your routers are not using RIP, you may also need static routes installed in your routers. The principal is the same, but the syntax will vary by router.

There is a white paper for Win2K DHCP at:
http://www.microsoft.com/TechNet/win2000/win2ksrv/technote/dhcpnt5.asp
It is clear if you already know DHCP, but does not explain the basics of routing.

by mpdcsup

I'm going to take a stab at assuming you actually have clients on LAN A pinging each other and clients on LAN B pinging each other -- otherwise, you never would have been advised to add static route options in DHCP -- and that what you actually typed (LAN A clients can't ping each other) was a typo. If I'm wrong, RGershbock has already gone beyond the call of duty to help you.

The destination/router pairs should be added in sequence (e.g., pair1 is address1 and address2, pair2 is address3 and address4, etc.)

Keep in mind, if you have two routers, then there are really three segments.

What about other pinging scenarios? Can LAN B clients ping LAN A clients?

Are your default gateways setup?

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