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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: mail service with no mx (was - Re: Computer systems blamed forfeeble hurricane response?)
On Wed, 14 Sep 2005, Roy Badami wrote: william(at)elan> Could you elaborate on how firewall will william(at)elan> determine if the connection is from mail server william(at)elan> or from telnet on port 25? Perhaps because most telnet clients will attempt telnet option negotiation? If so one could avoid this by using a client such as netcat... Telnet option negotiation is at Layer 7 after TCP connection has been established. Firewalls typically don't operate at this level (TCP session is Layer 4 if I remember right) and would refuse or reject (difference type of ICMP response) based solely on attempt to connect to certain ip or certain TCP/UDP port. -- William Leibzon Elan Networks [email protected]
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