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Guest
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 Posted: Sun Nov 16, 2008 8:48 pm Post subject: gateway routing problem |
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hi all!
i have a really strange issue: i've been connecting to the internet
(at home) through a gateway with linux (fedora) for years. this
machine is connected to a usb adsl modem and to a switch. everything
was fine until my line got changed (automatically due to the end of a
service): differences were enhanced speed, dynamic ip instead of
static and pppoe instead of atm
well, since then (months) this happens: the gateway has absolutely no
problems connecting to the internet, while other computers cannot get
to other than google (!). dns works well: if i ping linux.com i get
its ip, but no packets can get through (with both local and remote
dns).
not think that sometimes, with no reason, it starts working (for some
minutes)...
now we're surfing thanks to squid, and recently a symptom added: if i
unset the proxy on my laptop i can surf on that pages i visited with
the proxy...
it isn't a problem with iptables because its configuration hasn't
changed during the adsl upgrade; however i tried to disable it, but
there's no difference
it is something related to the gateway (and not to the line), because
if i set another pc as gateway there's no problem...
so what should i look at?
i cannot reinstall the box, but i must solve this because the proxy
thing is too limiting!
thanks for you attention (and sorry for my english)!
alberto |
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Andy Furniss
Guest
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| Posted: Tue Nov 18, 2008 1:11 am Post subject: Re: gateway routing problem |
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villa.alberto@gmail.com wrote:
| Quote: | hi all!
i have a really strange issue: i've been connecting to the internet
(at home) through a gateway with linux (fedora) for years. this
machine is connected to a usb adsl modem and to a switch. everything
was fine until my line got changed (automatically due to the end of a
service): differences were enhanced speed, dynamic ip instead of
static and pppoe instead of atm
well, since then (months) this happens: the gateway has absolutely no
problems connecting to the internet, while other computers cannot get
to other than google (!). dns works well: if i ping linux.com i get
its ip, but no packets can get through (with both local and remote
dns).
not think that sometimes, with no reason, it starts working (for some
minutes)...
now we're surfing thanks to squid, and recently a symptom added: if i
unset the proxy on my laptop i can surf on that pages i visited with
the proxy...
it isn't a problem with iptables because its configuration hasn't
changed during the adsl upgrade; however i tried to disable it, but
there's no difference
it is something related to the gateway (and not to the line), because
if i set another pc as gateway there's no problem...
so what should i look at?
i cannot reinstall the box, but i must solve this because the proxy
thing is too limiting!
thanks for you attention (and sorry for my english)!
alberto
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It could be a MTU issue due to pppoe being limited to 1492.
Some pppoe clients will have an option to help, look for something to do
with mss/mtu clamping.
Alternately you could try iptables mss clamping (or you could just set
the MTUs on the PCs on the LAN to 1492).
Assuming wan is ppp0 and it has MTU set to 1492 -
iptables -t mangle -I POSTROUTING -p tcp --tcp-flags SYN,RST SYN -o ppp0
-j TCPMSS --clamp-mss-to-pmtu |
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Guest
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| Posted: Fri Nov 21, 2008 10:46 pm Post subject: Re: gateway routing problem |
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it is!!
setting my laptop mtu to 1492 (ifconfig interface mtu 1492, for
readers) fixed the problem! i'll fix that on the gateway soon
thank you very much!
Andy Furniss wrote:
| Quote: | It could be a MTU issue due to pppoe being limited to 1492.
Some pppoe clients will have an option to help, look for something to do
with mss/mtu clamping.
Alternately you could try iptables mss clamping (or you could just set
the MTUs on the PCs on the LAN to 1492).
Assuming wan is ppp0 and it has MTU set to 1492 -
iptables -t mangle -I POSTROUTING -p tcp --tcp-flags SYN,RST SYN -o ppp0
-j TCPMSS --clamp-mss-to-pmtu |
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