General (packet tracer) network problem

[john-]

Hi,

The problem I can't solve is like this:

4 subnets are all connected to a switch, the switch connects to a router and the router connects Back to the switch. Make it so that the subnets can reach each other. Not to use multiple routers or vlan switching...

No luck with static routes or interface exit (although I could be using it wrong). It looks like an old school problem before plan switching made it's way up. Packet tracer doesn't allow for secondary addresses on the router.

Could anybody explain or solve this problem?

John

[mattjones03]

Hi John,

Once you have configured the interfaces on the router, have you issued the command ‘no shutdown’.

To verify that the router interface is up, issue the following command;

‘show interface [Interface Reference]‘

Finally, just wanted to mention, you may be deploying the topology you have defined in this post for a good reason, however consider a router on a stick approach. This way you would have a trunk interface between the router and the switch preventing you having to utilise two router interfaces.

[john-]

Thanks for the reply,. The router is up and will exit nicely to the 40.0 subnet when pinged. It has a static route to exit on the interface.

When I would ping the 30.0 or 20.0 network it goes wrong. It does it's arp thing but I suspect that the switch is the bottleneck. Or maybe it's packet tracer?

I could slap a few routers in the field and a few switches, and that's what happens in all those tutorials. But think about it, before you know it you filled the rack and the cost will be staggering.

This is a concept problem for all I know it should work, it doesn't so I try to find out why. Is it me, doing some config thing wrong, is it packet tracer, or do I have to do something on the switch...

Anyway, please have another look, it's a nice networking problem. It brings us subnetting, routing on a small scale. 

John

[mattjones03]

Hi John,

Is there anyway you could share the packet tracer file with us?

[john-]

hi,

just change jpg to pkt

please use the simulator to follow a ping (imp and arp)

john

[Georg Pauwen]

Hello,

in addition to mattjones' post, have a look at the file below (rename it to .pkt), it is a Packet Tracer 7.1 file. With your requirements, you basically need 4 interfaces connected between the router and the switch. The router-on-a-stick approach mentioned would indeed be more efficient and require only one (trunk) link between the switch and the router.

[john-]

Hi,

I know that vlan's are a solution or multiple routers, but that question remains why does this not work in packet tracer? Why is a static route to a subnet not working? 

In simulation mode you can follow a ping and arp, and you will see that arp reaches the subnet's but it won't fill the routers table....

Please think about this in detail, I think it's a crucial networking thing...

thanks

John

change the .jpg to pkt 

[Georg Pauwen]

Hello,

--> In simulation mode you can follow a ping and arp, and you will see that arp reaches the subnet's but it won't fill the routers table....<--

What exactly do you mean by that ?

Your Vlan20 and Vlan30 devices have either no default gateway or the wrong default gateway configured. Either way, the default gateways do not exist anywhere.

[john-]

Hi,

I don't use vlan's! That is the point. When you ping from 10 to 30 and the router can't find 30, it uses arp to find 30. But it doesn't work. When you simulate this you can see the process working as described but no solution.

Perhaps the switch needs a config... Also when I put a static route up to 30 it still doesn't work, I find this strange.

any thoughts.

[Georg Pauwen]

I think first we need to understand what you are after:

1. Hosts in subnet 192.168.30.x are not configured with a default gateway

2. There is no layer 3 interface at all existing for hosts in subnet 192.168.30.x

3. Hosts from subnet 192.168.10.x need to reach hosts in subnet 192.168.30.x

Does that summarize it correctly ?

[john-]

Hi,

Everything is directly connected, the gateway doesn't affect anything. If I assign a gateway to 30 it doesn't change anything.

1. the subnets must be able to reach each other.

from 10 to 40 works because the router routes between them. It is possible to assign a secondary address but not in packet tracer.

2. I use fastethernet 1/0 as exit and in theory it should find 30 or 20 etc. So layer 3 is present.

3. all subnets should be able to reach each other.

[Georg Pauwen]

Hello,

2. I use fastethernet 1/0 as exit and in theory it should find 30 or 20 etc. So layer 3 is present.

FastEthernet1/0 is the default gateway only for the 192.168.40.x network. In order to assign a default gateway to the 30 network, there needs to actually BE a gateway.

This is getting really confusing. I think you need to dumb it down for us: what are you trying to achieve ? That all hosts in the 10 network are able to reach hosts in the 20 and 30 networks, without a default gateway and a layer 3 interface ?

[john-]

hi,

Remember there is a layer 3 device the router, when yo change it's fa1/0 ip you can ping the corresponding subnet. But you can also exit through the interface reaching all the subnets.

The Plan. add a static route to reach 1 off the subnets, later add static routes for all the subnets.

doesn't seem to work, why? It beets me.

It looks like ARP has a problem with the different subnets, the router should adjust this for the correct route. Somehow the router has to know about the subnets Mac and ip, fill it's table but how?

I tried it with the gateway and without, doesn't make a difference.

The goal is a thorough understanding of routing and networking. Like I said a real router has for instance a possibility for a secondary address, packet tracer not.

perhaps there is a routing protocol that can handle this I don't know. 

Why can't I ping between those subnets and how to solve that without vlan's or additional routers. 

John

[Georg Pauwen]

Hello John,

--> But you can also exit through the interface reaching all the subnets. <--

How is this supposed to work ? Maybe it would help if you can post a real live configuration of a router (with secondary addresses ?) which does what you want.

In addition, static routes won't do you any good, since all you have are connected interfaces, and those take precedence over any static route...