N
Nick Fotis
Good morning,
I became recently a systems administrator in our company. Some days ago (10
days, to be more exact) we noticed a very annoying and strange problem. Let
me offer some background first:
Servers: mostly Windows NT4 SP5 or so, which operate for some years now,
with SQL servers, Exchange, IIS, etc. Some of these IBM boxes are also
clustered.
The company premises are in 3 floors, and there are various versions of
Windows PC co-existing (from Windows98 to XP Professional). There are three
switches (Cisco Catalyst 2900 in the lower two floors, Cisco Catalyst 3500
in the 3rd floor), while two NT4 boxes serve as PDC and BDC and another one
serves as WINS server.
Ten days ago, some PCs in the 3rd floor (which is served from the Catalyst
3500) started being extremely slow in every thing these did in the network
(browsing, etc.), becoming nearly useless. Doing 'ping -t' showed packet
loss of 10-15% (that's unheard in a switched 100 Mbps network with 10 or so
PCs in a floor). The problem became worse later, with 1-2 more PCs slowing
to a crawl in network operations.
None of the other PCs had any problems, though (besides a master browser
election that was being forced from the PCs that had been slowed down).
Rebooting every troublesome PCs (and a server reboot for making sure nothing
was wedged), the trouble persisted. Mind you, we speak about a network that
was operating for months without any hint of problems, so we were baffled by
this. Doing a full scan with Norton Antivirus didn't uncover any active
virus/worm, and some infected files were quarantined.
An idea that was suggested by another colleague was to slow the Ethernet
connections of the troublesome PCs (most but not all of these have Intel
PRO/100 cards) to 10 Mbps - imagine our surprise when suddently these
started working again!
Any ideas of the cause of the problem??
I'm not very inclined to believe the 'problem cable' is the source of all
this - suddently one and a half rooms (with some exclusions in each room)
starting having problems sounds a bit strange to me (it's all done with Cat5
cabling).
I guess I'll have to ask for a cable test in order to be sure?
Hardware incompatibility? Most of the affected PCs have Intel Ethernet
cards, which are most common (and there are 1-2 Realtek cards in the mix).
Software incompatibility?? As far as I know, nothing has changed in the
software front (but some user may have put something that wreaks havoc in
the network - but
Thanks in advances for any ideas you can give on this.
Scratching head,
N.F.
I became recently a systems administrator in our company. Some days ago (10
days, to be more exact) we noticed a very annoying and strange problem. Let
me offer some background first:
Servers: mostly Windows NT4 SP5 or so, which operate for some years now,
with SQL servers, Exchange, IIS, etc. Some of these IBM boxes are also
clustered.
The company premises are in 3 floors, and there are various versions of
Windows PC co-existing (from Windows98 to XP Professional). There are three
switches (Cisco Catalyst 2900 in the lower two floors, Cisco Catalyst 3500
in the 3rd floor), while two NT4 boxes serve as PDC and BDC and another one
serves as WINS server.
Ten days ago, some PCs in the 3rd floor (which is served from the Catalyst
3500) started being extremely slow in every thing these did in the network
(browsing, etc.), becoming nearly useless. Doing 'ping -t' showed packet
loss of 10-15% (that's unheard in a switched 100 Mbps network with 10 or so
PCs in a floor). The problem became worse later, with 1-2 more PCs slowing
to a crawl in network operations.
None of the other PCs had any problems, though (besides a master browser
election that was being forced from the PCs that had been slowed down).
Rebooting every troublesome PCs (and a server reboot for making sure nothing
was wedged), the trouble persisted. Mind you, we speak about a network that
was operating for months without any hint of problems, so we were baffled by
this. Doing a full scan with Norton Antivirus didn't uncover any active
virus/worm, and some infected files were quarantined.
An idea that was suggested by another colleague was to slow the Ethernet
connections of the troublesome PCs (most but not all of these have Intel
PRO/100 cards) to 10 Mbps - imagine our surprise when suddently these
started working again!
Any ideas of the cause of the problem??
I'm not very inclined to believe the 'problem cable' is the source of all
this - suddently one and a half rooms (with some exclusions in each room)
starting having problems sounds a bit strange to me (it's all done with Cat5
cabling).
I guess I'll have to ask for a cable test in order to be sure?
Hardware incompatibility? Most of the affected PCs have Intel Ethernet
cards, which are most common (and there are 1-2 Realtek cards in the mix).
Software incompatibility?? As far as I know, nothing has changed in the
software front (but some user may have put something that wreaks havoc in
the network - but
Thanks in advances for any ideas you can give on this.
Scratching head,
N.F.