My computer connects to a LinkSys BEFSR41 router. This router connects to a Linksys EFSP42 PrintServer. The PrintServer connects to my HP 722C inkjet. The “use protocol analysis” in 2.3.3.33 beta prevents me from printing. When I click “print” I get a continuous stream of the following log errors:
Severity: High Reporter: Network Monitor Description: Blocked by Protocol Analysis (Invalid Flag Combination)
Details: Direction: TCP Incoming Source: 192.168.1.102:34443 (my printserver) Remote: 192.168.1.100:1057 (my computer) Reason: SYN ACK PSK is an invalid TCP combination.
When I uncheck “use protocol analysis” my printer works fine.
It would be nice if CPF worked with this sort of network printserver and still gave the added security of protocol analysis for internet traffic.
Yes. This type of non-standard packets are used by printer vendors. This is a violation of RFC standards. But we will remove this check to make your life easier.
I love this firewall, but it was blocking a network printer. The network was well-defined, by name and IP range. I read another user’s advice to uncheck “block fragmented ip datagrams”, and I tried, but it didn’t work.
Later, just looking around, under Network Monitor > Network Control Rules, I found one rule to block something… I could not understand in detail, but the rule seemed VERY general. I removed that rule (as well as one rule to allow globally GRE, which is Gretech’s GOM Media Player - - which now I know is totally not relevant to the printer problem… it’s just that I forgot what GRE was for that moment…). Anyway, after removing that block rule, the network printer could communicate fine. Somehow, that rule seemed to be there from the time I started using Comodo Firewall.
The printer is installed on this computer with Comdo installed. The other computer needing to communicate with this one has an older Zonealarm Fireall (maybe 3.1 or so), set up with the same network info.
I hope this helps… I was almost ready to abandon Comodo because of that small problem. I’ glad I looked around more.
(as well as one rule to allow globally GRE, which is Gretech's GOM Media Player - - which now I know is totally not relevant to the printer problem.. it's just that I forgot what GRE was for that moment...).
GRE is actually the Generic Routing Encapsulation Protocol and is used in conjunction with VPNs (Virtual Private Networks)