[tlug] Networking problem

["Jean-Christian Imbeault" <jean_christian@example.com>]

I'm having a bad networking day, again ...

The problem I am having is with "those people" that told me a class B hub 
was causing my problems ;)

I'm forced to think that my machines are improperly configured but I can't 
figure out where.

I have two set of servers on two different subnets. Inside a set the 
machines are connected to each other with an infamous class B switching hub.

The hub then plugs into the data center's network via the cable they 
provide. I'm told it's plugged into an L3 switch.

The problem I am seeing is the machines from one subnet get a really crappy 
transfer speed when connected to machines on the other subnet. Using proFTP 
and an 11MB file I see mximum speeds of  (8e+02 Kbytes/sec) or 6.4Mb/s on a 
100Mb/s line.

If I do the same transfer between machines on the same subnet I get (1.1e+04 
Kbytes/sec) or 88Mb/s.

I did a traceroute and the data came back ok, one hop to the DC switch and 
one hope to the target machine on the other subnet. So it doesn't look like 
a routing problem

To remove the hubs as a source of problems I plugged one machine from each 
subnet straight into the data center network but still saw the same problem.

We even had someone go to an Internet cafe with a T1 line and check the 
connection speeds. The results were strange in that connection to one subnet 
was ok but connectiong tothe other was slow.

That would seem to indicate a problem in my networking configuration for the 
machines on one subnet ... but I can see what it could be.

Can someone offer ideas as to what further tests I can do to isolate the 
problem.

Here id the `route` outputs from one machine on each subnet in case it 
helps.

This subnet is "ok" from the Internet cafe
[root@example.com]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use 
Iface
211.120.56.96   *               255.255.255.224 U     0      0        0 eth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
default         211.120.56.97   0.0.0.0         UG    0      0        0 eth0

This subnet is "slow" from the Internet cafe
[root@example.com]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use 
Iface
211.120.56.64   *               255.255.255.224 U     0      0        0 eth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
default         211.120.56.67   0.0.0.0         UG    0      0        0 eth0

Thanks for any suggestions!

Jc

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