topic Dropping packets when using smtp in Network Security

Dropping packets when using smtp

bennyPeoples — Fri, 21 Feb 2020 14:39:30 GMT

hi,

i have a 1941 router configured with a zone based firewall. All working fine except the smtp.

we can reseive mails trough pop3 and imap but cannot send trough smtp. I get the following drop to see.

"dropping tcp session x.x.x.x:63025 x.x.x.x du to RST inside current window with ip indent 0"

i have no idea why this is happening. Hope somebody is??

config attached.

Thank you!!

Re: Dropping packets when using smtp

Flavio Miranda — Mon, 06 Nov 2017 20:04:21 GMT

Hello @bennyPeoples

Try to enable packet inspection for SMTP:

ip inspect name inspection-name protocol

https://www.cisco.com/c/en/us/td/docs/routers/access/1800/1801/software/configuration/guide/scg/firewall.html#16883

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Re: Dropping packets when using smtp

bennyPeoples — Mon, 06 Nov 2017 20:17:41 GMT

this is what i get on logs.

*Nov 6 20:15:21.178: %APPFW-6-NBAR_PORT_HOP: smtp using 587 port - tcp session 192.168.1.117:63759 212.71.0.16:587 on zone-pair LAN-WAN class Others
R1(config-if)#
*Nov 6 20:15:35.210: %FW-6-DROP_PKT: Dropping tcp session 195.81.195.51:443 192.168.1.103:57796 due to policy match failure with ip ident 0

Could it be because the hoster smtp.edpnet.be is blacklisted? Because when i did this with my home account it works fine.

Re: Dropping packets when using smtp

Flavio Miranda — Mon, 06 Nov 2017 21:37:37 GMT

Probably. At least, you need to fix this anyway.

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