Static Routing

Unanswered Question
Jun 15th, 2010

Hi Everyone,

I have a questions about static routing. I am not sure if I have this configured right and was hoping someone could provide some help.

I have a Cisco 1841 and an ISP DSL Modem. The Cisco 1841 has two ethernet ports, 0/0 and 0/1.

0/0 is the LAN and DHCP pool, the settings are:

DHCP Pool Range - 192.168.30.100-192.168.30.199

IP address - 192.168.30.1

Default router IP address - 55.150.10.101

DNS Server - 70.84.2.10, 200.142.101.1

0/1 is connected to the ISP DSL Modem

IP address - 55.150.10.101

The ISP DSL Modem has a Static IP of 55.150.10.100

My question is, are these static routes correct for the 1841?

Route 1:

Destination Network Prefix: 0.0.0.0

Destination Network Mask: 0.0.0.0

Forwarding: 55.150.10.100

Route 2:

Destination Network Prefix: 55.150.10.101

Destination Network Mask: 255.255.255.255

Forwarding: Port 0/1

Route 3:

Destination Network Prefix: 55.150.10.101

Destination Network Mask: 255.255.255.255

Forwarding: 192.168.10.1 - Remote Site Local Address

Route 4:

Destination Network Prefix: 192.168.10.0

Destination Network Mask: 255.255.255.0

Forwarding: Port 0/1

Route 5:

Destination Network Prefix: 192.168.11.0

Destination Network Mask: 255.255.255.0

Forwarding: Port 0/1

I'm pretty sure they are right, but I having problems connecting a site to site VPN. I think that the VPN address is not connecting to the port 0/1.

Any help is very much appreciated.

Thanks, Jackie

I have this problem too.
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Richard Burts Tue, 06/15/2010 - 20:27

Jackie

I question the configuration of DHCP in what you have posted. In particular I believe there is a problem in your definition of the default router IP address. For DHCP clients their default router address should be a router interface in their subnet. Given what you have posted it would logically be 192.168.30.1 rather than 55.150.10.101.

As far as the static routes that you have listed:

- route 1 is the correct static default route.

- route 2 is a route to the router interface connected to the DSL modem. You do not need static routes to connected interfaces. delete this route.

- route 3 puzzles me. It starts off just like route 2 but the forwarding address is a surprise. Where and what is 192.168.10.1? delete this route.

- routes 4 and 5 also puzzle me. They seem to indicate that 192.168.10.0 and 192.168.11.0 are reached out the interface connected to the DSL modem. If that is the case then do not specify the outbound interface but specify the next hop address.

HTH

Rick

siclines1234 Tue, 06/15/2010 - 20:51

Rick,

I'm sorry, typo, the default router for the DHCP pool is 55.150.10.101, the ISP DSL Modem. 192.168.30.1 is IP for the port 0/0, the DHCP pool,

If I make the default router of the DHCP pool 192.168.30.1, the result is no internet for the LAN.

Route 3 forwarding address, 192.168.10.1, is the router at a remote site that I am trying to connect to over a VPN connection.

Route 4 and 5 - would the next hop address be the VPN site IP address or the local LAN router IP at the remote site?

Thanks for help Rick,

Jackie:)

Hitesh Vinzoda Tue, 06/15/2010 - 22:58

Hi

as you have default route on 1841 to DSL 55.150.10.101 no other routes are required. delete them except the default route, Also as suggest by other NP expert change the default router in DHCP to 1841's LAN side interface's IP address. I believe that NAT is performed on 1841

Again Remote site VPN addresses are covered under default route, no need to have separate routes for them.

HTH

Hitesh Vinzoda

Pls rate useful posts

Richard Burts Wed, 06/16/2010 - 06:22

Jackie

I am puzzled - you say typo and then seem to repeat the same as the original post.

My point is that most clients of DHCP expect the default router to be an address in the local subnet. This way they can ARP for the address of the default router. If the DHCP client addresses are in 192.168.30.0 and the default router is 55.150.10.101 then most clients will have a problem. You comment that if you make the default router 192.168.30.1 there is no Internet connectivity. Are you saying that with the default router set to 55.150.10.101 that clients do have Internet connectivity?

You do want 55.150.10.101 as the next hop for the routers default route but it does not seem right to me for it to be the default for the clients.

Perhaps I do not understand what you are trying to describe in route 3 or 4 or 5. What I see is a description of a destination 55.150.10.101 with a next hop of 192.168.10.1 which makes no sense. The destination is in a locally connected subnet and the next hop is a remote address.

Route 3:

Destination Network Prefix: 55.150.10.101

Destination  Network Mask: 255.255.255.255

Forwarding: 192.168.10.1 - Remote  Site Local Address

From what I see I think that you do not need either route 3 or 4 or 5. Having a correct default route will get you to the remote addresses and you do not need special static routes for them.

If you are having problems in establishing a VPN I suspect that the problem is something other than your static routes.

HTH

Rick

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