nanog mailing list archives
Re: Broadcast pings.
From: Dean Anderson <dean () av8 com>
Date: Tue, 23 Dec 1997 21:21:37 -0500
At 6:32 PM -0500 12/23/97, Phil Howard wrote:
When a packet arrives, take note of the interface and gateway it came from. Check the route tables for where a reply to this packet could be delivered. Don't choose only the best route, but compare where the packet came from with all valid reply routes (except broad defaults larger than a certain size that can be configured). If the packet came from where it is valid to reply, then allow the packet to proceed. If not, then discard it (an ICMP probably won't make it back to the right place anyway).
Actually, you want to check that it is reasonable for a packet with a particular source address to arrive on a particular interface. Packets from customers should only come from customer source addresses. (input filter on the customer link) Packets from you should only come from your IP space, or that which you transit for others. (transmit filter at your borders) All bad packets come from somewhere. All you can do is make sure they can't come from your customers. You can also try not to send them on to others. --Dean ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Plain Aviation, Inc dean () av8 com LAN/WAN/UNIX/NT/TCPIP http://www.av8.com ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Current thread:
- Broadcast pings. Jamie Scheinblum (Dec 22)
- Re: [nanog] Broadcast pings. Stephen Balbach (Dec 22)
- Re: Broadcast pings. Joe Shaw (Dec 23)
- Re: Broadcast pings. Stephen Balbach (Dec 23)
- Re: Broadcast pings. Phil Howard (Dec 23)
- Re: Broadcast pings. Paul Ferguson (Dec 23)
- Re: Broadcast pings. Dean Anderson (Dec 23)
- Message not available
- Re: Broadcast pings. Jay R. Ashworth (Dec 24)
- <Possible follow-ups>
- Re: Broadcast pings. Al Roethlisberger (Dec 22)
- RE: Broadcast pings. Al Roethlisberger (Dec 22)
- RE: Broadcast pings. Jamie Scheinblum (Dec 22)