why I'm unable to ping R2 ?

[AdamBudzinski]

hello guys,

consider the below topology. Why the hell I'm unable  to ping Router 1's Gig0/0 interface (IP 192.168.0.10) when I'm able to ping Router 0's Gig 0/1 interface (192.168.0.1) ?

Looking forward hearing from you !

Best Regards

Adam 

[Jon Marshall]

Adam

With routing you always need to check the path both ways.

I suspect if you check R1 you will find it does not have a route for the PC's subnet.

Jon

[AdamBudzinski]

Thank you both for looking in to this! 

But shouldn't I be still able to see packets on Router 0's Gig 0/1 interface? I mean the 192.168.0.0 is a directly connected network to both R1 and R0. So shouldn't the PING requests make it's way at least one way from PC to R1 ?

Thank you 

Adam 

[Jon Marshall]

Not sure what you are asking because you said you could ping 192.168.0.1 from the PC.

When you ping R1 from your PC the packets will get to R1 but when R1 does a route lookup for the PC's IP address it won't have one so it can't send the return packets.

Is that what you were asking ?

Jon

[AdamBudzinski]

"When you ping R1 from your PC the packets will get to R1 but when R1 does a route lookup for the PC's IP address it won't have one so it can't send the return packets."

But why I'm not able to see the packets on the Router 0's G0/1 interface when pinging from PC the Router 1's Gig0/0 interface ?

[Jon Marshall]

What exactly do you mean by see the packets.

You can ping that interface, do you mean you are trying to capture the packets ?

Jon

[AdamBudzinski]

Yes, I'm pinging Router 1 from PC and sniffing with Wireshark Router 0's Gig0/1 interface and I don't see any ICMP packets exiting it (I test it in GNS3 even though the picture is from Packet Tracer) 

Adam 

[Jon Marshall]

Okay, well you should see packets going to R1.

On R1 -

"debug ip packet"

and then ping from the PC.

Jon

[AdamBudzinski]

Hello guys,

I've started just now gns3 and loaded the lab again and ... this time I could see the pings, but yesterday I didn't capture any ICMP packets and this confused me and was the trigger to ask the questions! 

Thank you to you both for taking time to help me with this.  Your help is very appreciated.

BR

Adam 

[InayathUlla Sharieff]

As John said run the debug ip packet on router 1 followed by ping from pc.

you should see output like below:-

Router1#debug ip pack
Packet debugging is on
Router1#
IP: tableid=0, s=10.0.0.10 (FastEthernet0/0), d=192.168.0.10 (FastEthernet0/0), routed via RIB

IP: s=10.0.0.10 (FastEthernet0/0), d=192.168.0.10 (FastEthernet0/0), len 128, rcvd 3

IP: s=192.168.0.10 (local), d=10.0.0.10 len 128, unroutable

IP: tableid=0, s=10.0.0.10 (FastEthernet0/0), d=192.168.0.10 (FastEthernet0/0), routed via RIB

IP: s=10.0.0.10 (FastEthernet0/0), d=192.168.0.10 (FastEthernet0/0), len 128, rcvd 3

IP: s=192.168.0.10 (local), d=10.0.0.10 len 128, unroutable

Router1#
IP: tableid=0, s=10.0.0.10 (FastEthernet0/0), d=192.168.0.10 (FastEthernet0/0), routed via RIB

HTH

Regards

Inayath

[InayathUlla Sharieff]

Adam,

Its simple. Your pc has the DG configured hence it will be able to reach R0 connected interfaces.

example:

192.168.0.1--R0---10.0.0.1

PC will be able to ping 10.0.0.1 & 192.168.0.1

PC will not be able to ping 192.168.0.10 bcz it belongs to other router which is R1.

Reason: R1 doesnt have route back. R1 needs to have route back to reach the 10.x network. R1 will only be able to ping 192.168.0.10 and it will not be able to reach 10.0.0.1 which is configured on R1 other interface. Hence you need to have the route to configured on R1 to reach the 10.x network.

Hope this clarifies a bit. In case not please let us know.

Regards

Inayath

[InayathUlla Sharieff]

Adam,

Here is what you need to do.

1- On PC check the default gateway to be 10.0.0.1 ( To verfiy click on laptop -Desktop--ip configuration and make sure you see the default gateway address configured here).

Once this is done you are good at laptop side.

2- Now coming down to router 1 you need to have route to reach 10.x network.

configure:

ip route 10.0.0.0 255.255.255.255 192.168.0.1

You should be good to go.

REgards

Inayath

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