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TCP packet forwarding issue in router


Hi all,

I have an issue.

I have a router with 3 LAN and 1 WAN port.

I connected one pc to the LAN port and an another PC to the WAN port.

And tried to ping.I was able to ping the 2 PC's.

But the problem is when i tried to send some data ,server is immediately closing the connection.When i analysed using ip_conntrack tool i can see the paramater LAST_ACK send by the server.

That is data transfering is not happening.

How can i solve the issue.

Any help is appreciated

With Regards,


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2 Replies
New Contributor I

Hi Dhanya, how about connecting your server to the LAN ports and test the file transfer? this is to isolate the possible restriction of the router on the WAN port.

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Hi sage,

Thanks for your quick response.

My router is having 4 ports.3 are LAN ports and one WAN port.

I connected one PC to the LAN port 1 using an ethernet cable and one PC to WAN port using an ethernet cable.

I assigned a static IP address to PC connected to the WAN port.

Network settings in PC connected to WAN port are the follo.

IP address

Subnet mask

Default gateway

PC connected to the LAN port will get an IP address

Router IP address is

Ethernet as WAN IP address and remote IP address is

Testing Set Up 1:(Sending UDP packets):

Server side(PC connected to LAN port):

i run the application iperf -s -u

Client Side(PC connected to WAN port)

iperf -u -c

Result:UDP packets are receiving at the client side.

Testing Set up 2:(For sending TCP packets)

Server Side:

iperf -s

Clien Side

iperf -c


TCP packets not receiving at the server side.

When i analysed using ip_conntrack tool connection is establishing but server is sending LAST_ACK.

My aim is to send some TCP packets or video from WAN to LAN.

Any help is appreciated.

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