kwe@buit13.bu.edu (Kent England) (09/07/90)
>> Specifically, while just about every other network device or node will >> ignore the preamble as network "junk", the cisco picks it up as a >> network error. The solution is to place a filtering bridge between >> the Cisco(s) and any twisted-pair equipment. Ciscos should *not* be >> directly connected to either ODS or Synoptics hubs if you wish to >> avoid this situation. >> >I have heard before of problems with Cisco routers and short fragments. >Perhaps you should talk to people at Cisco about this. A short >fragment created by a collision is a normal part of Ethernet/IEEE 802.3 >network operation, not a network error. These fragments are not >specific to 10BASE-T operation only, they also occur on multi-segment >coax LANs. > >> Chuck Lukaszewski imp@osa.com 612 525-0000 >Pat Thaler Whether you call it a collision fragment or a network error is important to understanding what your interface counters are telling you, but I like the idea of having high-performance bridge/routers being able to give you "poor man's analyzer" counts on every LAN interface on the net. These are the interface counters I like: *broadcasts [broad- and multi-] *runts [any enet frame <64 bytes; ie collision fragment] *CRC [I presume on all frames] *frame ["usually the result of collisions or serial line noise"] collisions [number of retransmitted frames; ie "self-collisions"] interface resets And these summary stats: input errors [runts, giants, no in-buf, crc, frame, overrun, ignored] output errors [sum of all output errors] The * stats have global significance, according to my interpretation and so are useful as the "poor man's analyzer". The others only relate to the router interface. Don't classify runts as not worth counting because they aren't "official" errors. I'd like to know what the cisco sees. And don't assume a low collision count means a healthy network. A low *runt* count is a proper indicator of a healthy network. A high runt count combined with a low collision count just means you have a low-volume stream of traffic onto a possibly sick network. I like the runt count for that reason. Every other node gives me collision counts; only the high volume servers help me identify sick networks. The cisco, on the other hand, with its runt counter gives me a direct indicator of collision volume that the PCs/workstations don't give me with their counters. --Kent