iptables entries

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martinr
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Joined: 17 Mar 2014
Posts: 16
Location: Manchester, United Kingdom

PostPosted: Thu Apr 03, 2014 11:14    Post subject: iptables entries Reply with quote
I installed the mini DDWRT on my Linksys WRT54GL.

I have no intention of messing with iptables, but I want to understand it as part of general knowledge both of firewalls and networking.

The first few lines in my iptables are:

Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT 0 -- anywhere anywhere state RELATED,ESTABLISHED
DROP udp -- anywhere anywhere udp dpt:route
DROP udp -- anywhere anywhere udp dpt:route
ACCEPT udp -- anywhere anywhere udp dpt:route


1. Surely 2 identical lines to drop UDP is a mistake, only one would be needed?

2. Is the ACCEPT UDP after the DROP a mistake, because iptables would already have dropped it before it got to the ACCEPT?


As I say, I don't want to mess with it, merely to understand what I'm looking at.

Martin
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BasCom
DD-WRT Guru


Joined: 29 Jul 2009
Posts: 1229
Location: Germany

PostPosted: Thu Apr 03, 2014 12:49    Post subject: Reply with quote
you need to look more inside.

telnet into router and type

iptables -L INPUT -vvv.
it shows more detailed information.

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RT-N66U @ kongac Build 24200M K3.10.40
TL-WR842ND v1 @ BS-build 23919 WDS AP
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TL-WR841ND @ BS-build 23919 Client Bridge ( Routed )
martinr
DD-WRT Novice


Joined: 17 Mar 2014
Posts: 16
Location: Manchester, United Kingdom

PostPosted: Thu Apr 03, 2014 20:27    Post subject: Reply with quote
BasCom wrote:
you need to look more inside.

telnet into router and type

iptables -L INPUT -vvv.
it shows more detailed information.


Danke sehr!, BasCom.

I see what you mean. Furthermore, I now know how to telnet into my router (after having had to create a rule in my Windows Firewall).

I have learned a great deal by this little exercise.

Thank you very much for your kind help.

Martin



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BasCom
DD-WRT Guru


Joined: 29 Jul 2009
Posts: 1229
Location: Germany

PostPosted: Thu Apr 03, 2014 20:51    Post subject: Reply with quote
no problem.
_________________
RT-N66U @ kongac Build 24200M K3.10.40
TL-WR842ND v1 @ BS-build 23919 WDS AP
TL-WR841ND @ BS-build 23919 WDS Client
TL-WR841ND @ BS-build 23919 Client Bridge ( Routed )
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