Not the last word, but you imply that the collisions are only due to capacity... and I can have the wrong match on both ends and get plenty of collisions with no capacity issue.....and I reserve the last word as always for you...where have you been lately, I have missed you !!!! :)
Priscilla Oppenheimer wrote: >Larry Letterman wrote: > >>set one end to 100 half and the other to 100 full and see what >>happens....:) >> > >I mentioned the duplex mismatch problem too, but it has nothing to do with >his question or problem. > >The key to troubleshooting is to address the actual problem, not some >assumption you make about the problem. > >Thought you would have the last word, eh? :-) > >Priscilla > >>Priscilla Oppenheimer wrote: >> >>>Larry Letterman wrote: >>> >>>>Most likely the previous 10/half interface on the switch and >>>>the router >>>>were not >>>>linked at the same speed/duplex or the other router had an >>>>issue with >>>>the setting. >>>> >>>No, the switch and router were set to the same thing, which >>> >>was 10 Mbps half >> >>>duplex, if you read his messages. He was using a 2500 router. >>> >>Those routers >> >>>predate the full duplex standard. In fact they may predate 100 >>> >>Mbps also. He >> >>>had no choice but to upgrade the router, which he did. >>> >>>He was seeing lots of collisions, including excessive >>> >>collisions where the >> >>>frame got dropped because even after 15 retries it encountered >>> >>a collision. >> >>>Collisions are normal in shared (half-duplex) Ehternet, but >>> >>excessive >> >>>collisions are not. Collisions are caused by the stations on >>> >>the shared link >> >>>simultaneously sending. Excessive collisions are due to a >>> >>shortage of >> >>>capacity. One fix to the problem is to increase the capacity. >>> >>By jumping >> >>>10-fold from 10 Mbps to 100 Mbps, the risk of collisions, >>> >>especially >> >>>excessive collisions, goes way down. Since each frame takes >>> >>1/10th the >> >>>amount of time to send, the odds that some other station is >>> >>sending when >> >>>another station transmits (or retransmits) go way down. >>> >>>Increasing capacity used to be the only way we could upgrade >>> >>an Ethernet >> >>>network. Then the full-duplex standard came about. It can only >>> >>be used on a >> >>>point-to-point link where each side has its own dedicated >>> >>transmit path. In >> >>>other words, it's no longer shared Ethernet. There's no need >>> >>to sense >> >>>carrier to see if anyone else is sending, because there isn't >>> >>anyone else. >> >>>It's not multiple access. Receiving while you're sening is >>> >>legitimate, so >> >>>there's no need to check for collisions. It's no longer >>> >>CSMA/CD. Of course >> >>>the collision rate goes down. Collisions really have no >>> >>meaning in this >> >>>environment. If there are collisions, then there's probably a >>> >>duplex mismatch. >> >>>So, anyway, he improved matters in two ways: upgrading the >>> >>capacity and >> >>>moving to full duplex. >>> >>>I just wanted to add this theory discussion. It's not right to >>> >>say (as >> >>>someone else did) that collisions are "caused by" a >>> >>half-duplex setting. >> >>>Collisions are caused by two stations sending at once, which >>> >>tends to happen >> >>>more and more frequently when there's not enough capacity to >>> >>support the >> >>>sending behavior of the nodes on the shared network. To fix >>> >>the problem, you >> >>>can increase capacity or you can make the network not shared >>> >>by connecting >> >>>just two devices and using full duplex. >>> >>>_______________________________ >>> >>>Priscilla Oppenheimer >>>www.troubleshootingnetworks.com >>>www.priscilla.com >>> >>>>To be safe I would set the switch port and the router >>>> >>interface >> >>>>to >>>>100/full or 10/full >>>>and there should be no issues then. >>>> >>>>and yes, the fast ethernet in the 26XX/36XX routers are a >>>>better >>>>solution..... >>>> >>>>Larry Letterman >>>>Cisco IT-LAN , San Jose >>>> >>>>Cliff Cliff wrote: >>>> >>>>>Today, We are put 3660 router to their end, having >>>>> >>>>Fastethernet card, and >>>> >>>>>connected to their switch. >>>>> >>>>>They change their switch port as following: >>>>> >>>>>interface FastEthernet0/14 >>>>>load-interval 30 >>>>>duplex full >>>>> >>>>>so far, after observe serveral hours, there is no collision >>>>> >>as >> >>>>well as not >>>> >>>>>error message in our router. >>>>> >>>>>So, what's wrong? Is the fastethernet is better? or previous >>>>> >>>>setting that I >>>> >>>>>have is wrong? Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=58499&t=58389 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
