General discussion

Locked

Mixed half and full duplexing

By bobwelshjr ·
has anyone experienced any issues in a network environment where some of the physical cabling is 10Mbit only (2 pair) and some is 100Mbit, using Cisco catalyst switches set to autonegotiation of duplexing mode, where systems cannot find network mapsor other strange issues? We have a client that does not believe this could cause problems, while I am certain it has something to do with their issues and am looking for supporting documentation.
Thanks for the assistance.

Bob Welsh
MCSE, A+, CCNA

This conversation is currently closed to new comments.

7 total posts (Page 1 of 1)  
| Thread display: Collapse - | Expand +

All Comments

Collapse -

Mixed half and full duplexing

by don In reply to Mixed half and full duple ...

Wow! Two pair sounds more like RJ-11 than RJ-45. Nice switches and junk wiring can be tough, I think I would first insist on re-wiring with at least Cat 5. Some network cards do not cooperate and play well with others autonegotiating. And the two pair lines clearly cannot do full duplex. It would seem safest to set all the ports to half-duplex and, if possible 10BaseT to avoid problems unless speed is a real issue. But good cabling is the real issue.

Collapse -

Mixed half and full duplexing

by bobwelshjr In reply to Mixed half and full duple ...

The question was auto-closed by TechRepublic

Collapse -

Mixed half and full duplexing

by mrjay67 In reply to Mixed half and full duple ...

If you truly are using 2 pair(which is telephone style cable) than this is a part of the problem. Make sure you are using cat5 networking cable throught your LAN. In theory different speeds shouldnt cause a major issue other than with slower network connections on the 10Mb lines/PCs.

For a different option:
You didnt mention the OS of the PCs. I have seen in rare occasion where a win9x system for no good reason would not accept mapped drives from a network login script. We had to run a clean.bat from startup(placed in the registry) that manually deleted possible drive mappings. We then placed another batch file that remapped everything and would work fine. If the actual connectivity isnt a problem you could try this approach.
Ifconnectivity is an issue check wiring and also lower the PCs to 10Mb to test and see if it helps. Mixed environments can cause erratic behavior but is not supposed to. In theory if systems are set to autonegotiate they should work at the level they can handle rather its 10 or 100. You may also want to set things to be at half duplex. I have seen more often problems related to the duplex. If systems are connecting to a hub or router(which dont usually support full duplex like a switch) they wont communicate properly and will have network collisions. It looks like you are connecting to a cisco switch so this shouldnt be an issue but could be in a mixed environment. It sounds to me, if your cabling is lacking, that the systems may be tryingto negotiate higher than what they are able to across inadequate cable. You might also check for bad nic(s). A chattering NIC can cause odd behavior as well, they may let you connect but give you other odd issues like you describe or perhaps not letyou on to certain inter/intranet sites.
Just thought i'd throw in some added options.
Hope this helps

Jason

As I have found theory and real world do not always match.

Collapse -

Mixed half and full duplexing

by bobwelshjr In reply to Mixed half and full duple ...

The question was auto-closed by TechRepublic

Collapse -

Mixed half and full duplexing

by mshavrov In reply to Mixed half and full duple ...

If you really want to prove to client that it causes delays, check port counters on Cisco switches. Even 10 CRC errors, collisions, bad frames, etc shows media problems. According to Cisco, first thing to check if you have slow network response and port errors are: 1. Port speed set to AUTO. 2. Duplex set to HALF 3. Disabled PORTFAST. First I would reccomend is set all ports PORTFAST function to ENABLE (command depends on switch - "set spantree portfast 1/1-48 enable" or "interface fa0/1, spanning-tree portfast"). Then try to split 10 and 100 MBps PCs. If you have equal nmber of PCs, just use separete switches or configure half ports to FIXED 100/FULL for new PCs and AUTO (or FIXED) 10/HALF for old PCs. With Half-duplex you may have collisions since both devices, PC and switch talks to single pair. And check your PCs, and configure them to FIXED Spedd and duplex.

Good luck.

Collapse -

Mixed half and full duplexing

by bobwelshjr In reply to Mixed half and full duple ...

The question was auto-closed by TechRepublic

Collapse -

Mixed half and full duplexing

by bobwelshjr In reply to Mixed half and full duple ...

This question was auto closed due to inactivity

Back to Networks Forum
7 total posts (Page 1 of 1)  

Hardware Forums