*SOLVED*Packet Loss in a two computers network (crossover cable used)

[slicksilver]

I'm having a very strange problem and I'm not even sure where to what to start with for a solution. Its like this....We have two computers in the office and both the systems are connected with a crossover cable. When I ping the other computer there is atleast more than 50% packet loss. Similiarily if I try pinging from the other computer the result is same i.e + 50% packet loss. What could be the problem here? I've been trying all kinds of solutions from the last couple of days without success.

Setup :

Both the computers have Windows XP with SP1 and all the critical updates.
One comp has Netgear FA311 Fast Ethernet Adaptor and the other has a Dlink (Realtek Chipset) card.
Both of them are connected with a AVAYA CAT5e cable which is 15mts in length.
The cables have been crossed perfectly. I used the anandtech FAQs to do this.

Sharing is enabled and all the below rules are being followed :

- All PCs have TCP/IP installed.
- All PCs have Netbios over TCP/IP enabled.
- All PCs have the same workgroup.
- All PCs have a unique computer name.
- ALL PCs have network shares defined.
- ALL NICS are on the same subnet (e.g. IP 192.168.0.* subnet mask 255.255.255.0).
- MS Client and file & printer sharing are checked on each NIC.
- All NICs have their node type = anything except p-node (peer to peer, or point-point). Check at cmd prompt with Ipconfig /all (XP/W2K) or winipcfg (W9X).
- XP's ICF firewall is permanently disabled.
- All 3rd party firewalls are disabled, uninstalled and deleted (until connection is working).


Where could I possibly go wrong?

Thanks

Raj

 

[ScottMac]

Force both NICs to 10Mbps / Half Duplex.

If the traffic stats improve, chances are your cable are not terminated well or have other problems.

Good Luck

Scott

 

[spidey07]

Did you modify the cable in any way shape or form? Trying to cut and re-crimp a patch cord is just about impossible to get right because the cable is stranded...causes all kinds of physical layer problems.

Try swapping the cable with a store bought crossover.

 

[slicksilver]

I still dont know why this is happening. I've changed the cable from AVAYA Cat5e to AMP Netconnect Cat5e and the problem still persists.

One very important observation is(after trying out scott's tip) is that there is no packet loss when I switch the card to 10mbps mode. What does this mean? I've already changed the cable twice and double checked the connectors.....

Thanks

Raj

 

[spidey07]

Originally posted by: rajkanneganti
I still dont know why this is happening. I've changed the cable from AVAYA Cat5e to AMP Netconnect Cat5e and the problem still persists.

One very important observation is(after trying out scott's tip) is that there is no packet loss when I switch the card to 10mbps mode. What does this mean? I've already changed the cable twice and double checked the connectors.....

Thanks

Raj

Generally if it runs at 10 but not 100 then you're got a cable problem.

you need a crossover cable.

If you're using a store bought crossover cable (and don't have any funky modifications) then we can look elsewhere.

 

[slicksilver]

Man...that guy is gonna be pissed...i've already changed the cable twice....but I need to sory my problem out first so hopefully he will understand. I ask him everytime if he has checked it and he says yes. Then I ask him if he can ping between two comps without packet loss ...then he tells me that they dont do ping and all those tests....all they do is test for continuity using some electrical instrument. These guys are in the business from 1985.

Btw, the cable I purchased is not a pre made crossover cable. I choose the length and they give me that much cable and then they put the connectors and crimp it. We dont get pre made or factory made crossover cables in India. Instead we choose what length what we want and they guy will fix the cable.

Thanks

Raj

 

[spidey07]

gotcha on the cable. I still think that is the problem but we can look elsewhere. "generally" when pings are sporadic you start troubleshooting at the lowest layer (cable...rule that out) then NIC (rule that out) then IP stack/drivers, then OS, etc.

let us know what you found out!

 

[buleyb]

go buy a store made crossover to verify they make good cables. its $5 well spent.

 

[narzy]

if you wern't in india I'd send you one I know works.

 

[buleyb]

man, I must be the only person on here who doesn't look at profiles...poo on me

 

[JesseKnows]

FWIW, I remember a Microsoft knowledge base article discouraging the use of a crossover cable between two computers. A quick search I just ran did NOT find it. Rather MS suggests using a crossover cable to interconnect servers for management. Hmmm.

Are you getting any "network disconnected" events? Check the system log. If you do, see Q239924 in MSKB. Maybe disabling the media sense feature will reduce your error rate (wouldn't completely remove errors, just reduce their impact).

 

[d3n]

I am inclined to agree about the previous suggestion concerning the media sense feature being enabled on the NIC interfaces.
If possible set both NIC cards to 100 Fixed / Full Duplex. If ether system were to try and 'auto sense' the connection it could cause your ping packets to drop or collide during the 'auto sense' negotiation.


I have a policy of always trying to set servers to fixed settings to preclude a network device or the nic from auto negotiating the connection down to half duplex per say. (which would knock your throughput on a 10Mb connection down to 1.5 MB or lower)

 

[Abzstrak]

you can try putting another NIC in too, in each machine or just one at a time... I'd bet on the cable though like everyone else, or something causing EM interfernence next to the cable.... I've hear of people running them right past MRI machines and all kinds of stupid things.

 

[d3n]

Originally posted by: Abzstrak
you can try putting another NIC in too, in each machine or just one at a time... I'd bet on the cable though like everyone else, or something causing EM interfernence next to the cable.... I've hear of people running them right past MRI machines and all kinds of stupid things.

possible, but I might have a hard time beliving that it would exactly 50% loss due to EMI... It might come up 100% packet loss for a minute or two and then be just fine with a 0% loss.

 

[JonnyBlaze]

i thought when you use a cross over cable you wont get 100 for full duplex. try forcing 10 with half duplex.

JB

 

[Abzstrak]

Originally posted by: JonnyBlaze
i thought when you use a cross over cable you wont get 100 for full duplex. try forcing 10 with half duplex.

JB

well, considering the way you do the wiring for cross-overs, you should be doing full duplex perfectly, half duplex might not even work, I don't think it would work right, but haven't tried it....

I also fail to see why you wouldn't be able to maintain 100mbps...

 

[slicksilver]

Finally I have found the answer to my problems!!! After losing hope and deciding that I will stick to 10mbps ...I finally gave it one last chance and finally it worked and is perfectly running. No it was not the cable..........it was an IRQ problem. Windows did not show any problem whatsover nor did anything look amiss so I was almost cent percent sure that it could have not have been a card problem. There was one thing that caught my eye in the device manager. I noticed that the adapter's IRQ and the internal modem's IRQ was same. For some reason although both of them were working ....I felt that it was not right for two devices to share the IRQ. So I shifted the modem to another PCI slot and made sure that it had its own IRQ. Then I pinged again and ....Voila! Everything is perfect.......Now everything is back to normal and now we have a happy 100mbps network ....

Thanks everyone for all the help.......I've always heard of people having problems with IRQs and all but it never happened to me in my 10 yrs of computing life........I guess there is always a first time for everyone

Raj

I just called the store owner and told him I got the problem fixed. He was really happy coz. all the time he was saying that it was not his cable fault. I coudn't blame him as well. Changed the cable thrice.....and all the three times he changed the keystone jacks as well. The cables he gave me were good quality ones....AVAYA, AMP NETCONNECT and D-LINK......