simple networking problem can ping gateway but not out

centosnewbie · 09-15-2006, 01:28 AM

so...i had everything working and of course i had to move onto messing with apache and opening port 82 to run it.

it seems somewhere in the middle of this i lost my access to the internet via all my client computers. i can still ping the gateway, access it via telnet, open it in samba...i just cannot access the outside.

i've tried restarting dns, network, so on. i just cannot figure it out this time. i know i had this happen before but i cannot remember the fix.

please help me! lol

Nathanael · 09-15-2006, 02:12 AM

first try to find where the problem lies: gateway -> internet, or client -> internet

if the gateway can get to the internet, then there is a problem with either:
iptables on gateway
ipforwarding state on gateway
routing table on client
dns settings on client

if the gateway cannot get into the internet check:
routing table on gateway,
check dns settings on gateway
iptables on gateway (esp. Policies)
or something between gateway and internet (ADSL ROUTER/MODEM)

centosnewbie · 09-15-2006, 02:32 AM

thanks

it seems all the client-side stuff hasn't changed (i'm not exactly newb with wind0ze) and the forwarding is enabled...as for iptables, what would i look for?

oh yeah, the gateway can access the internet. my bad in forgetting to state that in the first post.

centosnewbie · 09-15-2006, 02:51 AM

god i'm an idiot...

PHP Code:



/sbin/iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE

there...done...i guess i'm tired.

Nathanael · 09-15-2006, 04:01 AM

just in case you have a static ip: the man pages for iptables state it is better to use the target SNAT rather than MANGLE (again: only if you have a static ip)

centosnewbie · 09-15-2006, 08:25 AM

seems the server went down...still looking through messages why...but somehow i cannot connect to the internet again. gah, this is getting annoying.

and yeah, my ip is dynamic. dhcp external/internal.

any ideas?