Adam Hardy on 19/10/10 23:16, wrote:
My version of traceroute also has the --mtu option, which tries to
determine the MTU for the route being traced. It looks perhaps like the
firewall for interactivebrokers (IP 208.192.181.62) *may* be blocking too
many ICMP control message types - including the MTU/Fragment messages.
The problem is, it doesn't look good from their point of view. I have a
problem but their other 150,000 customers don't. I have a manually
configured gateway, iptables firewall and all - their other 150,000
customers use mostly windows, although there are an unknown number of
linux users out there - it's a java app.
I have so far only a couple of things to go on - communication with
their server shows inexplicable MTU behaviour, and there is a weak link
on the British Telecom part of the traceroute.
All tests on my LAN show that I am running normally though. I've tested
my mtu size, my firewall, my DHCP, my DNS (now using OpenDNS).
Just remembered that my DSL modem has some dumb iptables firewall with the
following rules:
Trying 192.168.1.1...
Connected to 192.168.1.1.
Escape character is '^]'.
login: root
Password:
BusyBox v0.61.pre (2004.06.18-02:49+0000) Built-in shell (ash)
Enter 'help' for a list of built-in commands.
# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
TCPMSS tcp -- anywhere anywhere tcp
flags:SYN,RST/SYN TCPMSS set 1460
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
DROP icmp -- anywhere anywhere icmp
destination-unreachable
DROP icmp -- anywhere anywhere state INVALID
Normally I log in and drop them all but sometimes after a reboot I forget and
the mini-firewall remains in place while I'm trying to solve this networking
problem. Is there a test I can put in place to test that I remembered to disable
this mini-firewall?
Thanks
Adam
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