ARP problems 1

[billyz]

heres a weird one.

I have a switched network with about 125 clients. All connect to 9 3com 3300 switches. I use a PIX 515 for internet access and reporting.

One fine day, several workstations stop working (unable to access internet), they are unable to ping the default gatewway (which is the PIX), they can ping any other machine on the network, and other machines on the network can ping them (the pix cannot ping them)

wait -- it gets weirder (is weirder a word?)

the ones that dont work are all older Compaq Deskpro EN 450 wth the Intel Pro100 card. The newer compaq deskpros (the p1.3ghz) have the same card, but are fine.

WAIT !!! THERES MORE

i just purchased 5 new Deskpro Evos, and they CANNOT PING THE PIX !!!

ACK!

so what I did to figure this thing out is to manually add the MAC of one machine to the PIX's ARP cache, then it works, but i dont really see that as a good solution --

the pix's arp config is default settings, never changed.

now what???

-BillyZ

 

[yizhar]

HI.

One of the switch might be blocking the ARP broadcast requests.
Another option is a problematic NIC driver - check this out.

Now - are there any special configuration at the SWITCHes?
Send more details about the network design.
Are you using VLAN?
Are all machines in the same ip subnet?
Are all problematic machines connected to the same phisical switch?
What happens if you switch phisical places between a "good" workstation and a "bad" one?

Is the tcp/ip configuration exactly the same for all workstations?

Is the NIC driver the same?

Is the OS the same?

Bye
Yizhar Hurwitz

http://come.to/yizhar

http://teachers.sivan.co.il/yizhar

 

[billyz]

Hey Yizhar -- im a big fan !!! i read all your posts.

ok, enough sucking up.

here are the answers to your questions -- you may have something with the config of the switches...


Now - are there any special configuration at the SWITCHes?
All switches are set to default...now we have 3 floors, 3 switches each.

Send more details about the network design.
Are you using VLAN?
NO. it is setup as default, 1 vlan with all ports added.

Are all machines in the same ip subnet?
yes. 192.168.0.0/22 (192.168.0.1-3.254 255.255.252.0)

Are all problematic machines connected to the same phisical switch?
No -- it is in various floors.
What happens if you switch phisical places between a "good" workstation and a "bad" one?
if I plug in my laptop to the 'bad' port, it works, if i take that computer to another port, its still broke.

Is the tcp/ip configuration exactly the same for all workstations?
yes. DHCP

Is the NIC driver the same?
Yes. i tried several versions in debugging this. The default from Microsoft, the latest from Compaq, and one from Intel.

Is the OS the same?
windows 2000, sp2

all my switches are 3com 3300 running latest version (2.69)

 

[yizhar]

HI Again.

OK so it might be a switching issue - you should better add another post in a switching forum as well.

Tell us more about the phisical network structure, like:
How are the switches connected to each other?
You have 3 switch in each floor - so are they linked together via Ethernet ports or in another way?
What type of connection between floors?

And I know this sounds weird and probably won't help much, but if you're using WINS try to add a static entry for the pix. Yes I know, WINS translates name to ip and not ip to MAC, but try anyway...

You should also contact your 3COM support, and maybe invite a profesional network consultant to assist.

Segmenting the network might help in your case, and some reorganization of the SWITCH connections and placing the pix "in the middle" can also help.

These are my guesses...

Bye


Yizhar Hurwitz

http://come.to/yizhar

http://teachers.sivan.co.il/yizhar

 

[billyz]

I'll post this in the 3com forum also.

3 floors, each floor has 3 switches. Each of the group of switches are connected together using the 3com module. So each floor has a separate group.

I am not really in agreement with how this is setup, i Inherited this network, and am planning on improving the infrastructure.

Each floor is connected via a single ethernet port by a x-over.

Im not using WINS -- i am using a 100% Native windows 2000 Active Directory with DNS.

 

[billyz]

I fixed the problem by upgrading the flash to 6.2(1)

weird.

 

[yizhar]

HI.

What was the previous "bad" version of the pix?
Yizhar Hurwitz

http://come.to/yizhar

http://teachers.sivan.co.il/yizhar

 

[billyz]

6.1(1)

I looked and didn't see anything in the 'whats new'

could've been a corrupted image too i guess.

 

[Guest_imported]

I have same problem with catalyst 2900 can ping default gateway but not each other

 

[yizhar]

HI Jim.

Post a new thread with more info about your specific situation and configuration.

Are you using the "alias" command?

Bye
Yizhar Hurwitz

http://come.to/yizhar

http://teachers.sivan.co.il/yizhar