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WAN Internet routing

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by gordonhaas

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Have a privat wan (172.16.20x.xxx). At the MAIN location is a IBM RISC 6000 AIX server. It resides in the 172.16.202.xxx network (its host address is .130). Also on that network resides a LinkSys BEFSR11 DSL DHCP router (not using the Linksys as a DHCP device. Using it to bridge multiple PC's to a DSL modem with one Static IP). It is configured as part of the 172.16.202.xxx network/lan (its host address is .134). The PC's on the .202.xxx network/lan can access the Internet through the LinkSys BEFSR11 (as expected).

Have two point to point 56K digital lines with four CISCO 1601 routers. The two end networks are 172.16.205.xxx and 172.16.206.xxx respectfully. From the PC's on these remote networks/lans, applications on the IBM 6000 can be executed (via telnet terminal emulation connections). In other words the CISCOs are routing properly. The problem is I cannot access the Internet from these points. I am not seeing the diference between the two applications (the ones on the AIX and the one on the Linksys). This is not a static route problem by virtue of the AIX connection which is on the same network that the LinkSys is on. CISCO does not route to a host, it routes to a network. Is this a case where I must write s a script for IE, etc? In the name of detail the entire WAN is using a 255.255.255.192 mask. All hosts are using the upper subnet 128-192. Appreciate any help. CISCO correctly said it is not their problem.

Respectfully,
Gordon Haas

11 replies

by ckilday

Gordon,
Just curious, do you have a "default route" established for the Cisco routers? If the routers don't know what to do with packets destined for a subnet that they have no knowledge of, they will discard them. If you have IP routing turned on, you can do this by adding the cisco global command "ip classless" to the remote routers, and the router will forward all unknown destination packets to the best external connection and trust the router there to forward the packets on. If you haveIP routing disabled, you would need to establish an "ip default-gateway xxx.xxx.xxx.xxx" and point the remote router to the ip address of the local router (the one connected to the LinkSys). Just a thought.
ck

by gordonhaas

With regards to the "ip classless" specification the answere is yes on both the local and remote routers (all four of them). Also on the remote router the default gateway 0.0.0.0 0.0.0.0 172.16.204.140 is specified which is the serial interface on its local router. In addition, 172.16.202.128 255.255.255.192 172.16.202.140 is also specified on the remote router which is the subnet that the LinkSys and the AIX server reside on. As mentioned in the original question the primary application resident on the AIX Server can be executed without problem. Both local routers specifiy each other as default gateways 202.140 -> 202.141 & 202.141 - > 202.140. The AIX Server (202.130) points to the 202.140 router. This was necessary for the AIX server did not handle static routes very well (had to specify one default gateway ) so I decided to let the Cisco's do the routing from the AIX Server. Outside of the default gateways there are no static routes to the 202.128 network for the two local routers are on that network. Just seems somehow the LinkSys 202.134 can't be found? Cisco will not route to a host, only a network. Which is understandable. Thanks again. Would appreciate any further input.

by stillatit

There are multiple points where this may need a fix.

At the remote lan, on the computers, make sure that the cisco routers are the default gateway, not just that there is a route for your particular lan/wan.

As mentioned in the previous answer, the cisco routers need to point to the Linksys router as their default gateway. While the cisco routes to a network (your main lan), it needs to know where to send traffic for places not on your lan.

The linksys router needs a static route back to each of your remote lans via the appropriate cisco router.

Check the documentation on the Linksys and find out how many stations it will provide NAT for. Some of these DSL routers limit you to 30 stations.

Good luck.

by gordonhaas

Point 1 - all the PC's on the remote lans point to their corresponding routers as the default gateway.

Point 2 - the LinkSys is on the same lan/network that the AIX Server and the two local routers are on. Can not specify the LinkSys as a default gateway regarding the local routers for they specify each other as default gateways. This is so in order to route the proper data to the two remote sites.

Point 3 - Each local Cisco has static routes to the remote networks. Not sure if you aresaying the LinkSys itself needs static routes to the two Ciscos but this is a point now that I think about it.

Point 4 - According to LinkSys spec it is suppose to be able to handle up to 253 hosts using DHCP. I think with regards to NAT it is 100. Only have two pc's on the local net and one on each remote. Most of the other "windows" are dumb terminals.

Thanks again. Would Appreciate more feedback.

by stillatit

If you want traffic coming in from other networks to find the internet, the other routers MUST use the linksys as their default router. You can put static routes in them pointing at your other networks.

The default route is where "unknown destination" traffic is sent. Clearly, once you are on the subnet which contains the linksys, this needs to be the linksys, or there is no way to find the internet. If the routers point at each other, unknown traffic (like with an internet address) bounces around inside your net until the routers notice a loop and kill the packets.

Good luck.

by gordonhaas

You're a better man than I Gunga Din. As it turned out the default gateways I had on the two local Cisco routers were simply overkill. I had already created all the necessary static routes to insure proper routing between them with regards to the remote lans. When I changed the default gateways on the local routers to point to the LinkSys I was able to connect to the Internet from the remote lans. Thanks a bunch for you time and EXPERTISE.

by ckilday

Gordon,
I think RGershbock has hit on it. You said your local routers pointed to each other as the default route. If you know of an internet ip address you could try to perform a traceroute from one of the cisco routers. The remote router should show one hop to the local router and then you would see the trace bounce back and forth between the two local routers until it timed out. The local routers would just hop between each other. Do as RGershbock says and set up a default route to your linksys router from the local cisco boxes and you should get through. Best wishes.
ck

by gordonhaas

You are correct Mr. Gershbock hit the nail on the head. The one nuance I still don't see is how the LinkSys sends back to the local Ciscos. It has no default gateway but I have to assume that since it is on the 202.xxx network the same one that the local Ciscos are on they get to the Ciscos. Thanks for your input - I learned a lot on this one!!

by Former member

Make the default routes on your Cisco routers point to the DSL router or run a routing protocol on the DSL router, using the same routing protocols as the Ciscos' (RIP2).

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