Greetings,
I am experiencing persistent network connectivity problems with a Red Hat
linux
based USENET News server.
System Configuration:
Intel N440BX "Nightshade" Motherboard w/
on-board Intel EtherExpress Pro 10/100Mhz NIC
on-board Symbios 53C876 dual SCSI adapter
Dual P2 400Mhz Intel CPUS
ICP Vortex GDTH6527RP SCSI RAID dual-channel Adapter
SCSI CD-ROM attached to Symbios SCSI adapter
Kingston SCSI Drive shelf with 1 4Gig and 2 9Gig disks attached to
each channel of the Vortex card. 4Gig drives are RAID-1 mirrored,
the 9 Gig drives are a RAID-5 for the news spool.
System is currently running Red Hat Linux 6.0 w/ all current
erratta updates, linux kernel 2.2.9, and a recent snapshot of the
INN STABLE CVS source code branch.
Symptoms:
A couple weeks ago this system started having problems with the
Vortex card. It would suddenly stop communicating with the rest
of the system. On-going processes would run until they performed
a disk access and then hang waiting on the disk forever.
Upgrading the BIOS on the adapter and increasing the cache memory
from 4Meg to 16Meg corrected this problem.
During or immediately after the SCSI card problem the system
started displaying network connectivity problems. It would
suddenly drop all network connections and return 'connection
refused' errors on all ports, including telnet and nntp, EXCEPT
for FTP and lpd. A few minutes later the system would again allow
network connections. This cycle repeats itself ad nauseum with
random intervals of allowing and then denying connections. The
FTP and lpd ports never close though.
When I am logged into the console I am unable to telnet out of the
box when it is refusing connection. Netstat reveals that the
system still thinks it has off of its normal USENET newsfeed
connections, but no data is moving and just piles up in the TCP
send-queue buffers. Running tcpdump shows the system making many
arp requests for the default gateway and DNS requests for our
newsfeed neighbor machines. I am unable to find anything on the
network that might be causing these weird network connectivity
losses.
These symptoms began while the system was running Red hat Linux
5.2 with linux kernel 2.2.8. I tried upgrading to 2.2.9 with no
change in behaviour. I then re-installed the system with Red Hat
6.0 from the ground up and still experienced the same problems.
I have removed, cleaned, and reseated all network cards, cables,
and CPUs. We have also checked the network cable going back to
the switch and moved the machine from one switch port to another.
I am at a loss for what to do next and am considering swapping out the
motherboard at this point.
Has anyone else seen anything like this? or offer assistance?
--[Lance]
NIEHS ITSS Contract, SysAdmin Task
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