04-14-2009 11:50 PM - edited 03-11-2019 08:18 AM
Hello.
My Cisco ASA firewall is set to allow inbound HTTPS connections to a webserver, which works great.
Exemplified by the log entry below;
access-list outside_access_in permitted tcp outside/22.44.55.77(22913) -> inside/WEBSERVER(443) hit-cnt 1 first hit [0xdfea2982, 0x0]
However there is also a log entry reflecting traffic back to the client in the other direction "FROM" tcp/443.
access-list inside_access_in permitted tcp inside/WEBSERVER(443) -> outside/22.44.55.77(22913) hit-cnt 1 first hit [0xdfea2982, 0x0]
I was not expecting this entry or connection as I had planned to block all "outbound" connections from this server.
I thought the ASA would be aware of an already existing inbound connection and not need to establish outbound.
Can someone please explain this?
Thanks.
04-15-2009 01:10 AM
Hi,
The second access-list you have seen is for the return traffic to the originating source.
The traffic to secure webserver was initiated from outside zone with (SYN flag set). The server has to respond to the connection i.e allow the traffic through that session, server sends back (SYN/ACK) and other request-response via 443 to the source service port.
The acl you have seen is normal, it is dynamically opened by ASA and will shutdown as you terminate the session to the server.
04-15-2009 08:22 AM
couple of questions.
1) do you have a " service-policy " configured/applied globally on the firewall .
2) do you see hits in your ACL for the return traffic.
04-17-2009 02:08 AM
Hi.
Thanks for your reply.
1) there is no service policy
2) yes there are hits for the return traffic on the outbound ACL.
I would like to remove the ACL though as it is initiated inbound so should not be required?
04-17-2009 02:39 AM
Copy paste the below code after which you should not require an ACL for return traffic. This is supposed to be there by default . If this does not help, Pls post your configs.
!
class-map inspection_default
match default-inspection-traffic
!
policy-map global_policy
class inspection_default
inspect dns maximum-length 512
inspect ftp
inspect h323 h225
inspect h323 ras
inspect netbios
inspect rsh
inspect rtsp
inspect skinny
inspect esmtp
inspect sqlnet
inspect sunrpc
inspect tftp
inspect sip
inspect xdmcp
!
service-policy global_policy global
!
HTH
Vikram
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