10-20-2023 01:34 AM
Hello, I have trouble blocking outgoing smtp on my x670. I have this acl applied to config master of my sharing:
Policy: deny_smtp
entry port_25_tcp {
if match all {
source-address 10.0.0.0/8 ;
protocol tcp ;
destination-port 25 ;
}
then {
deny ;
}
}
entry port_25_udp {
if match all {
source-address 10.0.0.0/8 ;
protocol udp ;
destination-port 25 ;
}
then {
deny ;
}
}
enable sharing 40 grouping 35-44 algorithm address-based L3
configure access-list deny_smtp ports 40 egress
but whenever I try I still can access smtp servers outside. Am I doing something wrong here?
Solved! Go to Solution.
10-21-2023 02:32 PM - edited 10-21-2023 02:37 PM
You have to put the ACL on all ports in the LAG. Stupid, I know...
https://extreme-networks.my.site.com/ExtrArticleDetail?an=000087786
Since you have 10 ports in your LAG, 1/10th of the sessions will be blocked as expected. When you apply the ACL on all ports (35-44), it will behave as expected for all sessions.
Oh, and you can ditch the UDP part. SNMP is TCP, never UDP (as far as I know, never seen it). I assume you know already, but SMTP can also be run on ports 465 and 587 with encryption. Port 2525 is also popular in order to circumvent filters like this. Of course. anyone can setup a port forwarding or even an SMTP server that listens to any other port for SMTP if they like.
10-21-2023 02:32 PM - edited 10-21-2023 02:37 PM
You have to put the ACL on all ports in the LAG. Stupid, I know...
https://extreme-networks.my.site.com/ExtrArticleDetail?an=000087786
Since you have 10 ports in your LAG, 1/10th of the sessions will be blocked as expected. When you apply the ACL on all ports (35-44), it will behave as expected for all sessions.
Oh, and you can ditch the UDP part. SNMP is TCP, never UDP (as far as I know, never seen it). I assume you know already, but SMTP can also be run on ports 465 and 587 with encryption. Port 2525 is also popular in order to circumvent filters like this. Of course. anyone can setup a port forwarding or even an SMTP server that listens to any other port for SMTP if they like.
10-22-2023 11:31 PM
Thanks, that's what I thought might be the cause here. As for the UDP part somehow I can see some UDP packets sent over port 25 as well, so this is just to prevent that.