topic Akshay, in Network Security

Inbound TCP connection denied

ohareka70 — Tue, 12 Mar 2019 06:48:41 GMT

Hello,

I have a server on the corporate network and it has a rule on the firewall to allow it to talk out to another external IP for a winscp transfer over tpc/222

It was working ok but it stopped this week saying

Inbound TCP connection denied from 10.x.x.x/49578 to 172.x.x.x/222 flags SYN on interface inside

I am not seeing it hit the firewall except to say that its being denied by an Access Rule

Any ideas

Kevin

Hi Kevin,

Akshay Rastogi — Fri, 30 Oct 2015 16:49:38 GMT

Hi Kevin,

- Is there any recent changes made on the ASA?

- when you say you do not see it hitting the firewall; how did you check that? did you take any capture on these ingress and egress interface?

- could you please take the output of packet-tracer on the ASA.

'packet-tracer input <source interface> tcp <source-ip> 123445 <destination-ip> 222 detail' and check where it is dropping.

As you had mentioned it is being denied by ACL, try placing permit acl for this traffic on line 1 on that concerned access-list.

Also you could take captures on ASA. please take the capture with 'cap drop type asp-drop all' and see the output with 'show cap drop | in <source-ip>'

Please share your findings.

Regards,

Akshay Rastogi

Akshay,

ohareka70 — Fri, 30 Oct 2015 19:27:06 GMT

Akshay,

i did a packet capture wizard on the cisco asa but it only showed ingress traffic - no egress but it didnt show much anyway other than an attempt

I done the packet tracer on the cisco asa and it said that the traffic was being denied by the access-list ie it seen the traffic as denied all and ropped it. I know an acl was applied

So i checked the routing on the LAN. It turns out this traffic needed to be routed out a different Layer 3 device and routed out the one of the ohter firewalls ( we have 3 on different sites and they are all stand alone). The firewalls all have the same access list

Bit of a nightmare but routing was the problem and as soon as it routed out the correct firewall then the access list was permitted

Thanks for your help and looking forward to trying this command on Monday

....please take the capture with 'cap drop type asp-drop all' and see the output with 'show cap drop | in <source-ip>'

regards,

Kevin