Troubleshooting

Unusual Network Activity

■If there is more than one physical path between the switch and the other CDP device and STP is running on the switch, then STP will block the redundant link(s). In this case, the switch port on the remaining open link may not be a member of an untagged VLAN, or any untagged VLANs to which the port belongs may not have an IP address.

■The adjacent device’s CDP Neighbors table may be full. Refer to the documentation provided for the adjacent CDP device to determine the table’s capacity, and then view the device’s Neighbors table to determine whether it is full.

One or more CDP neighbors appear intermittently or not at all in the switch’s CDP Neighbors table. This may be caused by more than 60 neighboring devices sending CDP packets to the switch. Exceeding the 60-neighbor limit can occur, for example, where multiple 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 for 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 13-36.

IGMP-Related Problems

IP Multicast (IGMP) Traffic That Is Directed By IGMP Does Not Reach 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 verify whether an IP address is configured for the switch or VLAN, do either 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 Telnet to the Switch Console: If you can Telnet to the switch, then an IP address is configured.

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