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truc
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Joined: 25 Jul 2005
Posts: 3199
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 Posted: Mon Apr 16, 2012 9:52 am Post subject: obscure connection problem (windows OK/linux NOK) |
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Hello,
A friend of mine is facing a weird problem with his internet access(DHCP):
When plugging a computer with windows, everything works fine, but when he plugs in his linux laptop, he gets an IP via DHCP, but internet almost doesn't work:
if the first thing he does is a ping, the latency keeps increasing for no apparent reason:
| Code: | 64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=1 ttl=50 time=654 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=2 ttl=50 time=2777 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=3 ttl=50 time=7338 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=4 ttl=50 time=7716 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=5 ttl=50 time=630 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=6 ttl=50 time=635 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=7 ttl=50 time=688 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=8 ttl=50 time=644 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=9 ttl=50 time=649 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=10 ttl=50 time=659 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=11 ttl=50 time=640 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=12 ttl=50 time=644 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=13 ttl=50 time=654 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=14 ttl=50 time=615 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=15 ttl=50 time=655 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=16 ttl=50 time=719 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=17 ttl=50 time=639 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=18 ttl=50 time=639 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=19 ttl=50 time=1586 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=20 ttl=50 time=1257 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=21 ttl=50 time=7690 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=22 ttl=50 time=6980 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=21 ttl=50 time=7690 ms
64 bytes from mil01s16-in-f24.1e100.net (173.194.35.24): icmp_req=23 ttl=50 time=7425 ms |
TCP connections are only just worst, nothing is usable.
The thing is that I don't have access to his computer, I can only ask him to perform some tests then ask him to send me the result via email.
This isn't a MTU problem, I've asked him to lower it, but it didn't change anything.
He doesn't have a real public IP address, I know the ISP might do something weird(would not be the first time), but I just have no idea what. I'll ask him to capture some traffic from linux and windows, but right now, I'd like to know if you happen to have any idea on this?
Thanks a bunch!
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Jaglover
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Joined: 29 May 2005
Posts: 8291
Location: Saint Amant, Acadiana
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| Posted: Mon Apr 16, 2012 8:44 pm Post subject: |
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Knowing what ISP it is would help, right now we have even no clue what's the country. I hear in some countries NAT is done at ISP level and customers get addresses in private address range, is this what we are dealing here with?
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PaulBredbury
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Joined: 14 Jul 2005
Posts: 7310
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| Posted: Tue Apr 17, 2012 12:19 am Post subject: |
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Something to try:
echo 1 > /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_be_liberal |
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truc
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Joined: 25 Jul 2005
Posts: 3199
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| Posted: Tue Apr 17, 2012 8:19 am Post subject: |
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Jaglover, it is a _small_ ISP in Central African Republic called Telecel, I highly doubt you've ever heard of it before  , they have some public IPs, but AFAICT they are reserved for NAT 1:1 for some other privileged clients...
One thing to keep in mind is that they often don't know what they're doing. I know they use 'Cubika Sistema de gestion acceso a Internet' to manage their "clients" but I don't know if that's of any use for you to know
PaulBredbury, I'm not really confident about it since the problem affects every protocols. I've asked him to try it anyway. will report back.
Thank you both for your replies 
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