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I have a server running on CentOS 5.3 (a comet chat server, will have lots of tcp connections). Recently I found it was very slow (http service and ssh) so I use "ifconfig" command to figured out what happened.

eth0      Link encap:Ethernet  HWaddr 00:1C:C0:B5:D5:EA  
          inet addr:  Bcast:  Mask:
          inet6 addr: fe80::21c:c0ff:feb5:d5ea/64 Scope:Link
          RX packets:871861 errors:0 dropped:489662344145 overruns:0 frame:0
          TX packets:639044 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:207239658 (197.6 MiB)  TX bytes:169416201 (161.5 MiB)
          Interrupt:225 Base address:0x6000 

lo        Link encap:Local Loopback  
          inet addr:  Mask:
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:44497 errors:0 dropped:0 overruns:0 frame:0
          TX packets:44497 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:11470951 (10.9 MiB)  TX bytes:11470951 (10.9 MiB)

When I restart its network, all goes well. But after a period of time it will be slow again.

Can someone help?



As Rajat requested, I wlll post some information for diagnosing

 uname -a
Linux 2.6.18-128.el5 #1 SMP Wed Jan 21 10:41:14 EST 2009 x86_64 x86_64 x86_64 GNU/Linux

sudo /sbin/lspci | grep Ethernet
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03)

 sudo dmesg | grep eth0
eth0: RTL8168d/8111d at 0xffffc20000006000, 00:1c:c0:b5:d5:ea, XID 281000c0 IRQ 225
r8169: eth0: link up
r8169: eth0: link up
eth0: no IPv6 routers present
r8169: eth0: link up
eth0: no IPv6 routers present

 sudo /sbin/ethtool eth0
Settings for eth0:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full 
        Advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 0
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: pumbg
        Wake-on: p
        Current message level: 0x00000033 (51)
        Link detected: yes

sudo /sbin/ethtool -k eth0
Offload parameters for eth0:
Cannot get device udp large send offload settings: Operation not supported
rx-checksumming: on
tx-checksumming: off
scatter-gather: off
tcp segmentation offload: off
udp fragmentation offload: off
generic segmentation offload: off

 sudo /sbin/ethtool -S eth0
NIC statistics:
     tx_packets: 4483119
     rx_packets: 7443820
     tx_errors: 0
     rx_errors: 0
     rx_missed: 0
     align_errors: 0
     tx_single_collisions: 0
     tx_multi_collisions: 0
     unicast: 3591906
     broadcast: 442720
     multicast: 3851914
     tx_aborted: 0
     tx_underrun: 0
share|improve this question
how does link status look on the switch side? <mallicious_mode>RTL8168d - you see. there is your problem. realtek...</mallicious_mode> – pQd Aug 18 '09 at 8:36
up vote 7 down vote accepted

couple of things to check:

  • run ethtool eth0 and see what speed/duplex status you have on the interface, then check if switch on the port you connect your server to has the same settins [ expected are: full duplex, 100 or 1000 MBit/s. identical on both sides ]

  • if there is no duplex missmatch - check the switch port and the network interface - maybe one of them is faulty

  • check / replace the patch-cord, maybe it is faulty or goes along some source of interference

share|improve this answer

which network card are you using it is normally do with driver u can re install them

uname -a
lspci |grep Ethernet
dmesg |grep eth0
ethtool eth0
ethtool -k eth0
ethtool -S eth0

take the out put of this and post back

share|improve this answer
the question was what causes the problem, not how to cease it without fixing – asdmin Aug 16 '09 at 8:50
@Rajat, I will post the information you need soon – Mickey Shine Aug 18 '09 at 8:22
Sorry, seems can not post formatted text as commet. I will update my question soon – Mickey Shine Aug 18 '09 at 8:24
no pro i m also using same r8169 what i did come out of this i use r8101 driver from realtek so i suggest re-install the driver and try it should work – Rajat Aug 20 '09 at 13:50

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