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1721 Router Setup

thoppenrath
Level 1
Level 1

I trying a new post because I've simplified my setup. I'm just learning and I can't seem to get a simple example to work. Following is my setup, I want to be able to Ping the laptop on Network 2. I can telnet to the router and ping it but I can't ping it from network 1.

Below is the router config.

------------------------------------------------------------------------------------

show config

Using 677 out of 29688 bytes

!

! Last configuration change at 03:40:45 UTC Mon Mar 31 2008

! NVRAM config last updated at 03:40:53 UTC Mon Mar 31 2008

!

version 12.2

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname TestRouter

!

logging queue-limit 100

enable secret xxxx

enable password xxxx

!

ip subnet-zero

!

!

!

!

!

!

!

interface Ethernet0

ip address 10.20.20.77 255.255.255.0

half-duplex

!

interface FastEthernet0

ip address 10.10.7.1 255.255.0.0

speed auto

!

ip classless

no ip http server

!

!

!

line con 0

exec-timeout 0 0

password xxxx

login

line aux 0

line vty 0 4

password xxxx

login

!

end

Thanks!

19 Replies 19

Richard Burts
Hall of Fame
Hall of Fame

Tony

Your config is fairly straightforward. I do not see obvious issues with it. I am guessing that it is less a router issue and more of a laptop issue. It would help if you would post the output of show ip interface brief.

I am also a bit confused with your description of what the problem is. You say:"Ping the laptop on Network 2" but I am not clear which network is Network 2.

When you say that you can ping it from the router but not ping it from network 1 it suggests that the laptop does not have the correct default gateway configured. Can you tell us the IP address, subnet mask, and default gateway configured on the laptop?

HTH

Rick

HTH

Rick

Sorry, I fogot to include this...

Network 1 (Main)

Range 10.10.x.x

Sub 255.255.0.0

GW 10.10.2.1 (Internet Router)

Network 2 ( One laptop connected to a hub)

IP 10.20.20.50

Sub 255.255.255.0

GW 10.20.20.77

1721 Router e0 is plugged into small hub and f0 is plugged into Main Closet 4507.

I can't ping the laptop 10.20.20.50 on network 2 from my workstation 10.10.3.10 on network 1. Here is the ip int brief

TestRouter#show ip int brief

Interface IP-Address OK? Method Status Prot

ocol

FastEthernet0 10.10.7.1 YES NVRAM up up

Ethernet0 10.20.20.77 YES NVRAM up up

Tony

This additional information is helpful. It makes my request even more important: Can you tell us the IP address, subnet mask, and default gateway configured on the laptop?

At this point the symptoms strongly suggest that the laptop does not have the correct default gateway configured.

HTH

Rick

HTH

Rick

Network 2 really is only the laptop see below...

laptop

IP 10.20.20.50

Sub 255.255.255.0

GW 10.20.20.77

Uh, ok I'm on to something. I changed the default GW on my computer to 10.10.7.1 and I was able to ping the laptop. However, I can't ping from the laptop to my desktop.

wardp1000
Level 1
Level 1

Hi

I'm probably not qualified to answer this question and will probably be wrong but what I've noticed is:

1. The GW for Network 1 is 10.10.2.1, what is this and won't any traffic for other networks, ie. 10.20.20.0 be routed via this GW? Should the GW be 10.10.7.1 (FE0) or have I misunderstood your layout?

2. Would a 'sh ip route' be useful?

Thank you

Peter

Hi

I'm probably not qualified to answer this question and will probably be wrong but what I've noticed is:

1. The GW for Network 1 is 10.10.2.1, what is this and won't any traffic for other networks, ie. 10.20.20.0 be routed via this GW? Should the GW be 10.10.7.1 (FE0) or have I misunderstood your layout?

2. Would a 'sh ip route' be useful?

Thank you

Peter

P.S. And by the time I'd finished typing this up you'd already posted the solution :) At least I was on the right track.

Tony

I was correct about invalid default gateway - I just was focused on the wrong machine. I am glad that you are making progress.

As to why the laptop can not ping the desktop - my first guess is that the desktop may be running some firewall software that will not allow ping to the desktop. As a point of comparison, can the router ping the desktop?

Peter

You were indeed on the right track. Good for you.

HTH

Rick

HTH

Rick

Rick, yes the router can ping the desktop (10.10.3.10)

Your config shows that you have no routing protocol running to route the traffic between the two networks. You must enable a routing protocol or use static routes to allow the router to route between the two networks. I would suggest using RIPv2 for basic connectivity in this setup.

Try this:

Router(config)#router rip

Router(config)#version 2

Router(config)#network 10.20.20.0

Router(config)#network 10.10.0.0

Router(config)#exit

brian

While well intentioned, your response is not correct. On the 1721 router IP routing is enabled by default and the router will route between connected networks/subnets without needing any routing protocol.

You only need a routing protocol when there is some other device with which you want to exchange routing information. As long as we are talking about connected networks no routing protocol is required.

HTH

Rick

HTH

Rick

Tony

I am glad that we are making some progress where the desktop can ping the laptop. I believe that this indicates that the IP addressing, the subnet masks, and the default gateways are correct now.

I am a bit puzzled that the laptop can not ping to the desktop. If the router can ping to the desktop then it shows that the issue is not a firewall running on the desktop. So there is something else that is preventing the ping from the laptop to the desktop.

When the router does a ping to the desktop by default it will use the outbound interface address as the source address of the ping. I would like to ask you to do an extended ping on the router. In the extended ping specify the destination address as the desktop address and specify the source address as the Ethernet 0 interface address (the subnet of the laptop). Lets see if a ping from a remote address still works.

HTH

Rick

HTH

Rick

I just asked around the office for reassurance and every person I talked to says the 1721 does not route connected networks by default. Please try the posted config. You can ping the desktop and laptop from the router but cannot ping each other. This indicates a routing problem.

brian

In one of the messages in this thread Tony says:

I was able to ping the laptop. However, I can't ping from the laptop to my desktop.

I interpreted this to mean that the desktop was able to ping the laptop. Perhaps Tony can confirm that this is the case?

If true this contradicts your assertion that the 1721 does not route connected subnets without a routing protocol.

HTH

Rick

HTH

Rick
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