>I have every reason to believe the apparent large amount of multicast
>activity is incorrect. For one thing, it claims more multicast packets
>than total packets input:
>
>> 75179 packets input, 46122114 bytes, 0 no buffer
>> 0 watchdog, 97436 multicast
ISL vlan trunk encapsulation wraps each frame in a new frame with a
multicast dst addr. So all ISL-tagged traffic looks like mcast traffic
to a router interface that is clueless about counting ISL frames.
>I have done some experimentation on the unspecified output errors. It
>is clear that these errors are related to packet size, and presumably
>then also to the VLAN encapsulation used (ISL in this case). Using
>1482 byte packets (instead of 1500 byte) results in no errors. Using
>1484 to 1500 byte results in one error per packet - but the packets
>clearly get through to the other side and are valid IP packets (e.g.
>1500 byte pings are received by the other side and returned with no
>packet loss).
Correct, ISL encap overhead of 30 bytes causes oversized Ethernet
frames. A max-sized 1518-byte frame becomes 1548 bytes once it is
wrapped in an ISL frame for sending over a trunk.
Here's a link to info on the ISL vlan tagging scheme:
http://www.cisco.com/warp/public/741/4.html
-Charles
This archive was generated by hypermail 2b29 : Sun Aug 04 2002 - 04:12:24 EDT