|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Filtering Source Addresses on gw-internet
On Tue, 12 Aug 1997, C. Jon Larsen wrote: > > Thats what I thought at first. But if the permit comes first, then packets > with valid source addresses (a.b.c.d) get out because they pass that rule. > > So a packet built like: > > Source-> a.b.c.d Dest-> 172.17.0.0 > > will get out and be passed to the ISP, wasting bandwidth. Thats why I deny > them first, and then do the permit later on in the list. Ah...I wasn't reading your rules closely enough. As a trick to reduce access-list length on my internet gatway, I nailed up static routes like: ip route 208.215.0.0 255.255.240.0 null0 250 ip route 205.229.48.0 255.255.240.0 null0 250 ip route 10.0.0.0 255.0.0.0 null0 250 ip route 172.16.0.0 255.240.0.0 null0 250 ip route 192.168.0.0 255.255.0.0 null0 250 The first two are our netblocks. The rest just stop packets for the "private IP" nets from leaving our network. I also have access-list rules that prevent them from entering our network. I'm assuming here that route cache hits are faster than access-list testing. ------------------------------------------------------------------ Jon Lewis <[email protected]> | Unsolicited commercial e-mail will Network Administrator | be proof-read for $199/message. Florida Digital Turnpike | ______http://inorganic5.fdt.net/~jlewis/pgp for PGP public key____
|