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New Member

Static routes and ATM LAN connection

Hey listen, I got a 1721 (2) 2950, (1) 2820, and 1 3524. OK now the problem, all of this switches are cascaded and are used for our LAN. Very basic setup, just connectivity. By the way we use the 2820 switch with ATM module to connect to another office for internet use. The IP assignment is /23. Now on the other side where this ATM is terminated we have a couple of 8500 series ATM switches, using the same IP scheme but also we have some registered IP addresses there,

now yesterday we added a new building to our company. we purchased the 1721 and defined static routes 192.168.0.x /28. On the ethernet side on the new buildings router we are using 10.20.10.x /24.

On the main building side we ofcourse gave the the ethernet interface an IP address from our previous scheme of

Now the problem I can ping from serial to serial for the new connection between the buildings. I can even ping the ethernet interface of 10.20.10.x from the router also. Now when I go the previous switches, 2950, 2820, 3524, I can ping the atm side all the way, but when I try to ping the atm side from the router interface, I can only ping up to our subnet, Why cant I ping the network. My other switches can ping with no problem as I mentioned. The routers interface is connected directly to a port on the ATM switch. I tried the same gateway that the switches are configured with but I can not ping. Any suggestions?

New Member

Re: Static routes and ATM LAN connection

Your description isn't complete. If you use private address range and Internet connection, you must use NAT on the Internet router.

So you only need include new addresses 192.168 and 10.20.10 to NAT inside statement.

Proper addressing scheme allows to avoid any similar problems.

New Member

Re: Static routes and ATM LAN connection

Lets see if I can make it clear. There are three buildings involved.

1. Our building which contains two 2950 switches, one 3524 switch, one 2820 switch with ATM module and one 1721 router with wic. All of these devices are working fine except from the the router I can not ping certain addresses which I will explain later. All devices are connected to the 2820 swtich, the 2820 is connected to another building by way of fiber over ATM module.

Our LAN is 172.29.x.x/23, now on the other side of the ATM link is another IP assignment of 150.150.x.x/ 24, this assignment was not done by us. We are part of an a large organization and this is their own assignment. They assigned us our IP scheme. Anyway, like I said all switches can ping our 172.29.x.x and ofcourse across the atm we have three IP addresses there on the ATM switches. We ping all of these ok. We can also ping the 150.150..x.x. The 150.150.x.x consist of our proxy, and name server for the internet. Configured on 2820 is the name servers for IP scheme 150.150.x.x with default gateway of 172.29.x.x, which is the default for all the switches.

Now we just installed our 1721 here to connect to a new building using 192.168.0.x, so over the serial link we our using and 0.2. On our side 0.1, the ethernet address is from our subnet. On the 192.168. 0.2 serial link we are using 10.20.10.x. for the etherent port.

Ok I can ping the serial link from either side, I can pink both subnets from the 10.20.10 and vice-versa. But what I cant do is ping from the router to the 150.150.x.x. Recall we have three IP addresses on the other side of the ATM from our subnet of I can ping those from the router, because the ethernet port has the same IP subnet, but not beyond that. My question again is why can those switches ping the 150.150.x.x. and the router cant? being that the router is cascaded with the other switches.

I mean the router is connected to 2820 ATM switch by way of ethernet, so logically it should be able to ping it. Now you mentioned NAT and access list but before that why can't I get out? I mean i tried access list with the permit all just to see but nothing. Do I need a route (serial connection) to the other side of the ATM? That don't make sense because the switches can access the 150.150.x.x over the ATM. So I hope this clears it up and if you can, please provide some sample configs for the NAT and access list, should this be your suggestion for the fix.

Thank you

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