nanog mailing list archives
Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?)
From: "william(at)elan.net" <william () elan net>
Date: Tue, 13 Sep 2005 16:31:05 -0700 (PDT)
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 william () elan net
Current thread:
- Re: Computer systems blamed for feeble hurricane response?, (continued)
- Re: Computer systems blamed for feeble hurricane response? Steven M. Bellovin (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Joseph S D Yao (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Eric A. Hall (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? William Allen Simpson (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Valdis . Kletnieks (Sep 13)
- Message not available
- Re: Computer systems blamed for feeble hurricane response? Mike Tancsa (Sep 13)
- Re: Computer systems blamed for feeble hurricane response? Suresh Ramasubramanian (Sep 14)
- Re: Computer systems blamed for feeble hurricane response? Mike Tancsa (Sep 14)
- mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) william(at)elan.net (Sep 13)
- mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Roy Badami (Sep 13)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) william(at)elan.net (Sep 13)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Adam McKenna (Sep 13)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Crist Clark (Sep 13)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Steven M. Bellovin (Sep 13)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Dave Crocker (Sep 13)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Joseph S D Yao (Sep 14)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Robert E . Seastrom (Sep 14)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Joseph S D Yao (Sep 15)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Steven M. Bellovin (Sep 14)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Joseph S D Yao (Sep 13)
- Re: mail service with no mx (was - Re: Computer systems blamed for feeble hurricane response?) Tony Finch (Sep 14)