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Release Notes for the Catalyst 3750 Switch Cisco IOS Release 12.1(14)EA1

OL-4215-01

Limitations and Restrictions

• IGMP filtering is applied to packets that are forwarded through hardware. It is not applied to packets

that are forwarded through software. Hence, with multicast routing enabled, the first few packets are

sent from a port even when IGMP filtering is set to deny those groups on that port. There is no

workaround. (CSCdy82818)

• A static IP address might be removed when the previously acquired Dynamic Host Configuration

Protocol (DHCP) IP address lease expires.

This problem occurs under these conditions:

–

When the switch is booted without a configuration (no config.text file in Flash memory).

–

When the switch is connected to a DHCP server that is configured to give an address to it (the

dynamic IP address is assigned to VLAN 1).

–

When an IP address is configured on VLAN 1 before the dynamic address lease assigned to

VLAN 1 expires.

The workaround is to reconfigure the static IP address. (CSCea71176)

• The Catalyst 3750 switch treats frames received with mixed encapsulation (802.1Q and Inter-Switch

Link [ISL]) as frames with FCS errors, increments the error counters, and causes the LED to blink

amber. This happens when an ISL-unaware device receives an ISL-encapsulated packet and

forwards the frame to an 802.1Q trunk interface. There is no workaround. (CSCdz33708)

• IP-option software-forwarded traffic is sometimes leaked unnecessarily on a trunk port. Suppose the

trunk port in question is member of an IP multicast group in VLAN X, but it is not a member in

VLAN Y. In VLAN Y, there is another port that has membership to the group, and VLAN Y is the

output interface for the multicast route entry corresponding to the group. IP options traffic received

on an input interface VLAN (other than VLAN Y) is unnecessarily sent on the trunk port in VLAN

Y because the trunk port is forwarding in VLAN Y (even though the port has no group membership

in VLAN Y). There is no workaround. (CSCdz42909)

• Known unicast (secured addresses) are flooded within a bridge group under these conditions: If

secure addresses are learned or configured on a port and the VLAN on this port is part of a bridge

group, non-IP traffic destined to the secure addresses is flooded within the bridge group. The

workaround is to disable fallback bridging. To remove an interface from a bridge group and to

remove the bridge group, use the no bridge-group bridge-group interface configuration command.

Another workaround is to disable port security on all ports in all VLANs participating in fallback

bridging by using the no switchport port-security interface configuration command.

(CSCdz80499)

• When you use the ip access-group interface configuration command with a router ACL to deny

access to a group in a VLAN, multicast data to the group that is received in the VLAN is always

flooded in the VLAN regardless of IGMP group membership in the VLAN. This provides

reachability to directly connected clients, if any, in the VLAN. The workaround is to not apply a

router ACL set to deny access to a VLAN interface. Apply the security through other means; for

example, apply VLAN maps to the VLAN instead of using a router ACL for the group.

(CSCdz86110)

• SNAP-encapsulated IP packets are dropped without an error message being reported at the interface.

The switch does not support SNAP-encapsulated IP packets. There is no workaround.

(CSCdz89142)

• The switch does not create an adjacency table entry when the ARP timeout value is 15 seconds and

the ARP request times out.

The workaround is to not set an ARP timeout value lower than 120 seconds. (CSCea21674)

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