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Needed config details

ashz14387
Level 1
Level 1

I am using GNS3 in ubuntu 18.4 and right now i configure a tap interface and set iptables nat rules for the device inside the gns3 to connect to internet but say i have an infra like tap1->R1->R2->R3->R4->R5 with the below details

R1 - f0/0 - 10.0.0.1, f1/0 - 11.0.0.1

R2 - f0/0 -11.0.0.2, f1/0 - 12.0.0.1 similarly for other devices(R3,R4 & R5 were connected)

if i ping form the device r2 to google the source address will be my tap interface address but when i try to ping the device R2 (11.0.0.2) from ubuntu it was reachable. why

 

 

 

 

3 Replies 3

M02@rt37
VIP
VIP

Hello @ashz14387,

When you ping R2 (11.0.0.2) from Ubuntu, and it is reachable, it indicates that there is a path between your Ubuntu machine and R2, and the necessary routing is in place to establish connectivity.

The behavior you observe in terms of the source IP address depends on the network configuration, including NAT rules and routing settings. If your Ubuntu machine is configured to use NAT when sending traffic to the GNS3 network, the source IP address of the outgoing packets will be translated to the IP address of the interface through which the traffic is being sent (in this case, the tap interface). This translation allows the response packets to be routed back correctly.

On the other hand, when traffic originates from within the GNS3 network (e.g., from R2 to Google), the network routing directs the traffic directly to the internet without undergoing NAT translation. Therefore, the source IP address of the outgoing packets will be the IP address of R2's interface (11.0.0.2).

Please provide additional details about your GNS3 network configuration, NAT rules, and any specific issues you are facing in order to be more accurate.

Best regards
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Any of this issue first thing try tracoute see where traffic stop.

From there start troubleshooting.

ashz14387
Level 1
Level 1

Sorry for the inconvenience, when i try to ping from the R2 to ubuntu, it was not reachable

i.e when i try ping from ubuntu say 172.16.1.2 to R2 11.0.0.2 it was not reachable