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TCP Reset-O, Reset-I, FINS

Alvaro Rugama
Level 1
Level 1

Hi everyone

hope you can help me with this issue. I´m having problems when connecting to a web service on a device. My ASA has 3 active interfaces, one for the headquarter inside network (inside), one for the ISP connection (outside) and one for the remote sites that connects through a MPLS (WAN). I´m trying to stablish a connection to a web service on a printer from my headquarter to a remote office (from inside to WAN); but I´m having random error messages on the ASA´s monitor.

if I try to connect from my laptop I got this messages

bueno---fins.jpg

this is the connection from the inside to the WAN interface.

bueno---stablish-inside.jpg

this one shows the the connection has been stablish. No problems so far.

But when I try to connect from another PC I receive this messages

stablish-inside.jpg

this are the messages from inside to WAN

reset--o.jpg

this image shows that the connection has been reset. So no connection has been stablish between the devices. What does the Reset-O means? but sometimes I do not receive the TCP Reset-O message sometimes we get the TCP Reset-I message.

syn-timout---de-colorqube.jpg

you can see the TCP Rese-I message on the first Row.

Not so sure what is going on. some computer are able to access the web service other don´t. I also do some testing, use my ip address (that works fine) in the other PC, but the problem persist, even with my ip address. Antivirus, Windows firewall, antimalware, all are shutdown.

All computer on the remote office can localy access the service with no problem. however, they have problems accesing some service on the headquarters.

I have ACL in both, the inside and WAN interface that allowes communication between they, using the Packet Tracer tool on the ASDM I can se that the package are allowed in every port number, because I´m allowing all traffic with no exception.

acl-asa.jpg

can anyone help me with this?

Best Regards

Alvaro Rugama Cerda

1 Accepted Solution

Accepted Solutions

Hello Alvaro,

On the outside capture

Starting at packet 24 we can see how the Printer starts the TCP Graceful closure with the FIN packet.Packet 26 shows that the Client agreed the closure of the session and sends the FIN packet to close it.

Having 0 packets on the ASP capture means the ASA is not dropping the connection (ASP capture will show all of the packets being droped by the ASA).

Any other question?

Looking for some Networking Assistance? 
Contact me directly at jcarvaja@laguiadelnetworking.com

I will fix your problem ASAP.

Cheers,

Julio Carvajal Segura
http://laguiadelnetworking.com

Julio Carvajal
Senior Network Security and Core Specialist
CCIE #42930, 2xCCNP, JNCIP-SEC

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