Re: Inline IP_Forwarding and other simple questions?

[Matt Kettler <mkettler () evi-inc com>]

At 02:04 PM 12/23/2004, mdpeters wrote:
> Do I need to enable ip_forwarding on for the transparent bridge to work?

As I understand it, you explicitly MUST NOT enable ip_forwarding, otherwise 
your snort-inline is a "pass all".

> Do I need to install ebtables for inline to disrupt traffic or is 
> iptables, libnet, and libpcap all that I might need?

AFAIK you don't need ebtables.  You do need libipq for inline and libnet. 
This is how snort-inline attaches to iptables by using libipq instead of 
using libpcap.


>  It is my impression that iptables just firewalls with static rules.

On it's own, yes, but IPTables is VERY extensible via libipq..

That's where snort-inline comes in. Snort-inline interacts with iptables. 
It doesn't do things like create iptables rules to block packets, it the 
whole system becomes an iptables rule, it just happens to be a rule that 
runs snort instead of some simple expression.



> Do the snort rules running on the transparent inline snort box reset the 
> traffic that passes through using inline?

Depends on if you use DROP or SDROP :).. However, inline doesn't JUST reset 
the traffic.. it also prevents the packet from being forwarded at all. DROP 
will also reset, SDROP won't.


Snort 2.3's inline capacity is a direct port of snort-inline. You might 
want to check their FAQ for other info:

http://snort-inline.sourceforge.net/FAQ.html





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