iptables is not redirecting traffic

anandnenwani · 11-17-2011, 12:51 AM

I have linux squid server with two lan card
eth0 --> 192.168.0.x
eth1--> 10.230.5.x

and my squid is running well.

but i don't want to set browser's settings of clients.

as i tried

Code:

iptables -t nat -A PREROUTING -p tcp --dport 80 -i eth0 -j REDIRECT --to-port 3128 
iptables -t nat -A PREROUTING -p tcp --dport 80 -i eth1 -j REDIRECT --to-port 3128

but still this is not working.

KamasCZ · 11-17-2011, 03:48 AM

Can you do

Quote:

iptables -L -n

and

Code:

iptables -L -t nat -n

and post the results here?

The command you posted seems to be OK, so I thik it's some other firewall rule.

anandnenwani · 11-17-2011, 10:49 AM

iptables -t nat -L
output is:-

Quote:

Chain PREROUTING (policy ACCEPT)
target prot opt source destination
REDIRECT tcp -- anywhere anywhere tcp dpt:http redir ports 3128
REDIRECT tcp -- anywhere anywhere tcp dpt:http redir ports 3128

Chain POSTROUTING (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

iptables -L -n

output is:-

Quote:

Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:3128
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:3128
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80

Chain FORWARD (policy DROP)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

Chain RH-Firewall-1-INPUT (0 references)
target prot opt source destination

Please reply me

I tried alot but still it's not working what i m leaving something .??

Please check this one too, as i did these too..

http://www.linuxquestions.org/questi...8/#post4525479

KamasCZ · 11-18-2011, 03:32 AM

Hmm, nothing bad as I can see.
So, try to add

Code:

iptables -A POSTROUTING -t nat ! -d 10.230.5.0/24 -s 10.230.5.0/24 -j MASQUERADE

rule. This rule should be above the redirecting to squid.

This should give you access to networks behind the machine with squid.
Also check if you have enabled ip forwarding - do

Code:

cat /proc/sys/net/ipv4/ip_forward

result must be 1

Are the routing tables on machine with squid well configured?
try

Code:

route -n

and paste results here, also check routing table on windows gateway

Code:

route print

anandnenwani · 11-18-2011, 12:43 PM

These are the configurations are:-

and I checked ip_forward . it's is 1.

squid box:-
eth0--> 192.168.1.16
eth1--> 10.0.0.4

iptables -t nat -L

output is:-

Chain PREROUTING (policy ACCEPT)
target prot opt source destination
REDIRECT tcp -- anywhere anywhere tcp dpt:http redir ports 3128
REDIRECT tcp -- anywhere anywhere tcp dpt:http redir ports 3128

Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
MASQUERADE all -- 10.0.0.0/24 !10.0.0.0/24

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

# route -n

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth1
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0

I am not getting what is happening with me..

? i tried alot. am leaving something ..??? Please help..

anandnenwani · 11-18-2011, 12:47 PM

Please tell me few more steps which is important to configuring squid and ipptables REDIRECT traffics..????

Thank You so much..!!

anandnenwani · 11-19-2011, 11:34 PM

Quote:

Originally Posted by KamasCZ

Hmm, nothing bad as I can see.
So, try to add

Code:

iptables -A POSTROUTING -t nat ! -d 10.230.5.0/24 -s 10.230.5.0/24 -j MASQUERADE

rule. This rule should be above the redirecting to squid.

This should give you access to networks behind the machine with squid.
Also check if you have enabled ip forwarding - do

Code:

cat /proc/sys/net/ipv4/ip_forward

result must be 1

Are the routing tables on machine with squid well configured?
try

Code:

route -n

and paste results here, also check routing table on windows gateway

Code:

route print

I again did value 1 ip_forward it with Open SuSE 11.4 and it worked.....Thanku So much ....But Why Iptables is not working well in RHEL.