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=58487&t=58389 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
