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Configuring Cisco router 4451 for Internet Access

mm5451
Level 1
Level 1

I am trying to get my cisco router 4451 to route to my ISP, but have been unsuccessful. Here is what i have.

 

ge0/0/1

192.168.1.129 255.255.255.128

ge0/0/2

192.168.1.1 255.255.255.0

 

ISP Static Address

IP Address 50.78.70.245

50.78.70.252

Gateway 50.78.70.246

 

Need to have both ge networks to route to the ISP for internet access. Have tried using IP Route 0.0.0.0 0.0.0.0 of both ge networks but with no success, I have even taken an additional ge port and configured it with my ISP static info, but again unable to connect to the internet. I am also unable to ping any of the ISP addresses, from either of the ge networks, but can ping both ge networks.

50 Replies 50

I have looked at what you have posted. There may be multiple things to address and I will start with 2 major issues.

1) the addressing of your serial interfaces will not work. Both serial interfaces have IP addresses in the same network (100.100.100.0/24). I am surprised that you were able to get it into the configuration. You can not have the same subnet operate successfully on 2 physically separated links. You need to change the addressing so that B to A is one subnet and B to C is a different subnet. You might solve this by dividing your /24 into 2 subnets. But for a point to point serial connection all you really need is a /30 subnet (255.255.255.252). So your first step should be to change the addressing and subnetting of the serial interfaces.

2) router B has 3 static default routes configured. That is 2 too many.

- You have a default route on B with the next hop being the address of router A. This is good and you should keep it.

- You have a static default with the next hop being the address of router C. The syntax is ok. But this route makes no logical sense. Remember that the default route is used when you are not sure where the destination really is. It makes no sense to forward a packet for an unknown destination to C. What can C do with it? So remove this default route.

- You have a static default with the next hop being the provider address. You are correct that this is ultimately where we want the packet to an unknown destination to go. But router B has no information about where the ISP address really is and so would not be able to insert this default route into the routing table. Remove this default route.

 

Fix these 2 issues and let us know how things are working.

 

HTH

 

Rick

HTH

Rick

Fixed the issues you suggested, I have attached a new network layout, So with the changes from Router B:

I can ping all serial interfaces on Router A, B, C

I can ping both local GE interfaces on Router B

I can ping all GE interfaces on Router A

I can ping the 50.78.70.245 on Router A

Unable to Ping the ISP Gateway of 50.78.70.246

Unable to ping the GE interfaces on Router C

 

Additional Info:

Router C

I can ping 100.100.200.2

I can Ping 100.100.200.1

I can Ping 100.100.100.2

I can ping both GE interfaces on Router B

Unable to ping anything on Router A or any of the interfaces of the ISP

Have attached an updated copy of config for router B and C

We are making progress. Glad to know that issues that I identified are resolved. I see the next issues that need to be addressed and they involve routing. As you start to address this you need to make a decision about how you want to handle routing for this network. You can continue to use static routes or you can decide that you want to run a dynamic routing protocol. Either choice can work. For a small network like this static routes might be appropriate. Perhaps dynamic routing protocol might provide more of a learning experience. Let me know which option you want to use.

 

Here is what I see of the current issue. On router B you have a static default route with router A as the next hop. This means that all interfaces of router B can forward traffic to router A. But it means that router B does not know how to reach any interface of router C other than the connected serial interface. So you will need to do something so that router B knows about subnets of router C (either more static routes or run a dynamic routing protocol).

 

On router C you have configured 2 static default routes. One of the default routes has the next hop of 100.100.200.1. This is to router B and should work ok. The other static default route has the next hop of 100.100.100.1 which is router A. But router C has no knowledge of where 100.100.100 is and this static default route will not work and you should remove it.

 

We do not know at this point what is the situation of router A but I am guessing that router A does not have routes to the subnets of B or C. The solution could be more static routes or could be a dynamic routing protocol.

 

Let us know what direction you want to go.

 

HTH

 

Rick

HTH

Rick

corrected router c route and probably would like to stay with static routes.

so from Router B i can ping 100.100.100.1 on router a

                                           192.168.1.129 on router a

                                            192.168.1.1 on router a

                                             50.78.70.245 on router a

                            unable to ping 50.78.70.246 on router a which is the ISP Gateway for internet access.

also from router b i can ping 100.100.200.2 on router c

as you stated i am unable to ping 192.168.4.1 or 192.168.5.1 on router c

 

From Router c I can ping 100.100.200.1 on Router B

                       I can ping 100.100.100.2 on router B

    Unable to ping anything on Router A

This is about where I am at, So I would like to work Router B being able to ping ISP router Gateway of 50.78.70.246

Thanks you have help me alot

All

from router a

can ping serial1/0/0 100.100.100.1

can both ge interfaces 192.168.1.129 and 192.168.1.1

can ping ge0/0/0 50.78.70.245

can ping isp gateway of 50.78.70.246

I have a pc on a switch connected to ge0/0/1 it can browse the internet

can ping serial 1/0/0 100.100.100.2 on router b

unable to ping anything on the other side of serial2/0/0 on router b

and same goes for anything on router c

 

Thanks for the clarification that you will continue to use static routes. In that case you will need to do these things:

- on router A you will need to configure static routes for each of the subnets of router B and of router C. For these static routes on router A the next hop should be the IP of the connected serial interface on router B.

- on router B the static default route will take care of access of subnets on router A and the Internet. You will need to add static routes for each of the subnets on router C and the next hop of these static routes should be the IP of the connected serial interface on router C.

- on router C the static default route should take care of access to subnets of router B, router A, and the Internet.

 

You have mentioned an issue with the other routers attempting to ping the address of the ISP interface. I am guessing that you have not yet configured address translation for the subnets of router B and C. If you configure the address translation then they should be able to ping the ISP address (and to access the Internet).

 

HTH

 

Rick

HTH

Rick

thanks, router b can ping all interfaces on the network, with the exception of the ISP gateway of 50.78.70.245, working on the address translation for that. from router c the only address i can ping 100.100.200.1 on router b, so i guess i will need to add statics routes for the subnet on router c, not sure why iam unable to ping past the 100.100.200.1 address.

wow, sorry, my bag, i guess i removed the static route from router c, i added it back and from router c i can ping all the interfaces on router c and b but iam still unable to ping any interfaces on router a, suggestions.

 

also router a for some reason can only ping serial interface 1/0/0 ip 100.100.100.2 router b, but unable to ping serial interface 2/0/0 ip 100.100.200.1, which are on the same physical router, for some reason network seems unable to communicate across both serial interfaces either from router c or from router a, like there is some type of disconnect between serial interfaces on router b, suggestions

add a small diagram

Your diagram mentions that there is no physical connection between A and C and suggests that this may be why you can not ping between them. There is no requirement for a physical connection to be able to ping. If you can not ping between A and C there are 2 things that can cause this. I will describe them for A pinging to C and a similar explanation fits C to A:

1) It may be that A does not have a route to the subnets of C and therefore can not send the ping request. The solution is to configure static routes on A for the subnets of C. Note that these static routes would specify the next hop as the serial interface  IP of B.

2) It may be that C does not have a route to the subnets of A and therefore when C receives the ping request from A that C is not able to send the ping response. The solution is to configure static routes on C for the subnets of A. Note that these static routes would specify the next hop as the serial interface IP of B.

 

HTH

 

Rick

HTH

Rick

working on the static routes,

 

but I am unable to ping the second serial interface on router b from router a.

 

ping from router a to 100.100.100.2 which is the first serial interface on router b, this works

 

Ping from router a to 100.100.200.1 which is the second serial interface on router b, does not work.

 

I put in a static route on router a next hop of 100.100.200.1

I put in a static route on router b next hop of 100.100.100.1

No effect, still unable to either interface

There has been so many changes, iam a little lost, i have made some progress, but still having problems, i have attached a network chart for reference, and a config file all 3 routers, look them over and advise what i am doing wrong.

Mike

I have looked at the new configs that you posted. I see changes that have been made. And I see some issues that you need to address.

1) on router A you have configured address translation that will translate traffic from 192.168.1.0 but not from any other subnet in your network. This is part of why B and C do not have Internet access.

2) on router A you have static routes for the LAN subnets of router C (which is good) but they have next hop configured as 200.200.200.1. But router A does not know where network 200.200.200 is and so would follow the default route. You need to change the next hop of both of these routes to 100.100.100.2.

3) on router B you have a static route for network 100.100.100.0. You do not need this static route (because router B knows this network as a connected route) and also the syntax of this static route is not correct. So remove this static route.

4) on router B you do not have a static default route. You need to configure a static default route with next hop of 100.100.100.1.

5) on router C you have a static default route with next hop of 100.100.100.2. But router C has no knowledge of where network 100.100.100 is. You need to change the next hop of the static default route to 200.200.200.1.

 

HTH

 

Rick

HTH

Rick
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