[clug] Networking slows down to unusable levels until restarted; Fast upon resumption

[Christopher Giffard]

I'm having an interesting/frustrating networking issue - I'm hoping  
somebody has seen this before, because I'm about to tear my hair out!

I recently installed a new gateway server on my work network, but kept  
the disk from the old one, and did a quick brain transplant yesterday  
night, just dropping the old disk into the new server. It seemed to be  
holding up then - but today networking is as contrary as I've ever  
seen it. Upon rebooting, network connectivity rapidly slows down to a  
level where SSH connections I have open to the gateway take 10 or more  
seconds to transmit a single keypress - but as soon as I restart  
networking by issuing '/etc/init.d/networking restart', the speed  
returns... for a minute or so - and then I'm dealing with incredibly  
slow networking again.

I've patched things together in an embarrassingly ugly way by dropping  
the network restart init script in a minute-over-minute cron-job,  
which seems to be keeping things vaguely usable for the people in the  
office. Unfortunately my network tech is on holiday, so I'll have to  
come up with a proper solution before he gets back.

The server runs Ubuntu Server 8.10 (2.6.27-11-server) and has two  
gigabit network cards:

*-network:0
     description: Ethernet interface
     product: IP1000 Family Gigabit Ethernet
     vendor: Sundance Technology Inc / IC Plus Corp
     physical id: 0
     bus info: pci at 0000:04:00.0
     logical name: eth1
     version: 41
     serial: 00:1d:60:5c:83:34
     size: 100MB/s
     capacity: 100MB/s
     width: 32 bits
     clock: 66MHz
     capabilities: pm bus_master cap_list ethernet physical tp mii  
10bt 10bt-fd 100bt 100bt-fd autonegotiation
     configuration: autonegotiation=on broadcast=yes driver=Sundance  
Technology IPG Triple-Speed Ethernet duplex=full ip=192.168.0.1  
latency=64 maxlatency=10 mingnt=80 module=ipg multicast=yes port=MII  
speed=100MB/s
*-network:1
     description: Ethernet interface
     product: RTL-8169 Gigabit Ethernet
     vendor: Realtek Semiconductor Co., Ltd.
     physical id: 1
     bus info: pci at 0000:04:01.0
     logical name: eth2
     version: 10
     serial: 00:21:27:c9:18:83
     size: 100MB/s
     capacity: 1GB/s
     width: 32 bits
     clock: 66MHz
     capabilities: pm bus_master cap_list ethernet physical tp mii  
10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
     configuration: autonegotiation=on broadcast=yes driver=r8169  
driverversion=2.3LK-NAPI duplex=full latency=64 link=yes maxlatency=64  
mingnt=32 module=r8169 multicast=yes port=MII speed=100MB/s

eth1 is the internal interface, and eth2 is the external interface,  
which connects to a VDSL modem on Transact over PPPOE.

Any help would be greatly, greatly appreciated!

Regards,
Christopher Giffard