NAT or internal servers with "real" IP addresses using NAT 0 can access anything until you block it. Outbound requests (such as http, ftp, etc) are all enabled by default. Users outside the firewall cannot access internal IPs without access-list or conduit statements.
In short, all outbound enabled and all inbound disabled by default. For your conduit permit icmp any any I would enable echo reply only rather than full icmp. Echo reply only allows replies back to the person pinging or tracerouting. Full icmp can be exploited in DOS attacks. example: access-list 10 permit icmp any any echo-reply access-group 10 interface outside (apply one to interface inside for outbound) Allen ----- Original Message ----- From: Steve Alston To: Sent: Wednesday, November 28, 2001 4:08 PM Subject: Re: PIX conduit & access lists [7:26684] > Patrick & Allen, > Thanks for the responses -- helps loads. I'm still slightly confused. > > I did a clear conduit expecting to block all incoming traffic. Following > the clear conduit, I did a show conduit to verify there were not any > conduits in operation. At that time, I was still able to receive web > traffic at my workstation. For that matter, the conduit statements only > applied to specific servers so why am I able to receive http at my > workstation? I did try to PING an IP address which failed when I removed > the conduits and worked when I restored "conduit permit icmp any any" -- > that behaved as expected. > > > Thanks, > Steve > > ""Allen May"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Very true and a good point, but the original question was about conduits > > which only apply to lower->higher. Higher->lower requires NAT. I > > accidentally typed access-list below but meant conduit. ;) *slap self & > get > > more coffee*. It still applies but wasn't what I meant to say. > > > > Thanks for pointing that out though. > > > > > > ----- Original Message ----- > > From: Patrick W. Bass > > To: > > Sent: Sunday, November 25, 2001 10:14 PM > > Subject: Re: PIX conduit & access lists [7:26684] > > > > > > > ""Allen May"" wrote in message > > > news:[EMAIL PROTECTED]... > > > > I'm not sure if this was answered or not, but a firewall always > assumes > > a > > > > deny all at the end of the access-list for inbound. Outbound is > > different > > > > since it allows all by default. > > > > > > > > > > Remeber this: Higher security level to lower security level, implicitly > > > allowed. Lower security level to higher security level, implicitly > > denied. > > > Otherwise it gets tricky once you start messing with multipile DMZs. > > > > > > > Also, access-lists are the way to go since conduits will be phased out > > in > > > > the near future. > > > > > > > > Allen > > > > > > > > ----- Original Message ----- > > > > From: Steve Alston > > > > To: > > > > Sent: Monday, November 19, 2001 9:25 AM > > > > Subject: Re: PIX conduit & access lists [7:26684] > > > > > > > > > > > > > Carroll, > > > > > Thanks for the reply. I'm using conduits now, but will switch to > > > access > > > > > lists in the future. (I'd like to fully understand the > configuration > > I > > > > > inherited before I start making changes) Are implicit denys > inserted > > > > behind > > > > > each conduit as well? > > > > > > > > > > > > > > > ""Carroll Kong"" wrote in message > > > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > > > Implicit denys behind every access-list are inserted. Are you > > > > > > mixing conduits and access-lists? You really should not. Use ALL > > > > > conduits > > > > > > or ALL access-lists. If both are used, conduits take priority and > > > > > override > > > > > > your access-lists. Access-lists are first match, conduits are any > > > > match. > > > > > > > > > > > > At 09:24 AM 11/19/01 -0500, Steve Alston wrote: > > > > > > >Does the PIX 506 require an explicit deny statement after setting > > up > > > a > > > > > > >permit conduit or access list. > > > > > > > > > > > > > >I appear to be receiving more traffic (e.g. NTP) than my conduit > > > > > statements > > > > > > >allow. > > > > > > > > > > > > > >Thanks much, > > > > > > >Steve > > > > > > -Carroll Kong Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=27642&t=26684 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
