Installation guide

Release Notes for the Cisco ME 3400 Ethernet Access Switch, Cisco IOS Release 12.2(44)SE

OL-14632-01

Limitations and Restrictions

These are the IP limitations:

• Subnetwork Access Protocol (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 adjacent 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)

MAC Addressing

This is the MAC addressing limitation:

When a MAC address is configured for filtering on the internal VLAN of a routed port, incoming packets

from the MAC address to the routed port are not dropped. (CSCeb67937)

Multicasting

These are the multicasting limitations:

• The switch does not support tunnel interfaces, including DVMRP and PIM tunneling.

• Nonreverse-path forwarded (RPF) IP multicast traffic to a group that is bridged in a VLAN is leaked

onto a trunk port in the VLAN even if the port is not a member of the group in the VLAN, but it is

a member of the group in another VLAN. Because unnecessary traffic is sent on the trunk port, it

reduces the bandwidth of the port. There is no workaround for this problem because non-RPF traffic

is continuous in certain topologies. As long as the trunk port is a member of the group in at least one

VLAN, this problem occurs for the non-RPF traffic. (CSCdu25219)

• If the number of multicast routes and Internet Group Management Protocol (IGMP) groups are more

than the maximum number specified by the show sdm prefer global configuration command, the

traffic received on unknown groups is flooded in the received VLAN even though the show ip igmp

snooping multicast-table privileged EXEC command output shows otherwise. The workaround is

to reduce the number of multicast routes and IGMP snooping groups to less than the maximum

supported value. (CSCdy09008)

• 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)

• When you use the ip access-group interface configuration command with a router access control

list (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)