18-8
Troubleshooting
Unusual Network Activity
Troubleshooting
One or more CDP neighbors appear intermittently or not at all in the
switch’s CDP Neighbors table. This may be c aused by mor e than 60 nei gh-
boring devices sending CDP packets to the switch. Exceeding the 60-neighbor
limit can occur, for example, where multi ple neighbors are connected to the
switch through non-CDP devices such as many hubs.
The Same CDP Switch or Router Appears on More Than One Port in
the CDP Neighbors Table. Where CDP is running, a switch or router that is
the STP root transmits outbound CDP packets over all links, including redun-
dant links that STP may be blocking in non-root devices. In this case, the non-
root device shows an entry in its CDP Neighbors table f or every port on which
it receives a CDP packet from the root device . See “Effect of Spanning Tree
(STP) On CDP Packet Transmission” on page 12-23.
IGMP-Related Problems
IP M ul ti ca st (I GM P) Tra ff ic Th at Is Di re ct ed By IG MP Do es No t R ea ch
IGMP Hosts or a Multicast Router Connected to a Port. IGMP must
be enabled on the switch and the affected port must be configured for “Auto”
or “Forward” operation.
IP Multicast Traffic Floods Out All Ports; IGMP Does Not Appear To
Filter Traffic. The IGMP feature does not operate if the switch or VLAN does
not have an IP address configured manually or obtained through DHCP/Bootp.
To v er if y wh et h er an I P a dd r es s is co n fi gu r ed fo r th e s w it ch o r V L AN , d o ei th e r
of the following:
■Try Using the Web Browser Interface: If you can access the web
browser interface, then an IP address is configured.
■ Try To Teln et to the Swi tch Con sol e: If you can Telnet to the switch,
then an IP address is configured.
■Using the Switch Console Interface: From the Main Menu, check the
Management Address Information screen by clicking on
1. Status and Counters
2. Switch Management Address Information