Motorola WS5100 manual Configuring Layer 3 Mobility

Switch Services 5-35

•Whenever the cluster protocol is disabled, a member switch forgets the learned cluster license as well as peer information needed to compute license totals.

•If the switch start-up configuration is removed, a member switch forgets the learned cluster license as well as peer information needed to compute license totals.

•If adding a new switch (with zero or non-zero installed license) to a group with at least one license contributing switch down, the new group member will receive a different cluster license value.

For example, for a cluster of three switches (S1 = 6, S2 = 6 and S3 = 6 licenses), the group license count is 18. If S1 goes down, the license count is still 18, since the license calculation is not initiated if a member switch goes down. If S4 (with zero licenses) is introduced, S4 becomes part of the group (can exchange updates and other packets), but has license count of 12 (NOT 18), even though S2 and S3 still show a license count of 18. This should be an indicator a new member has been introduced during a period when the redundancy group is not operating with all its license contributing members.

5.5Layer 3 Mobility

Refer to the following sections to configure Layer 3 Mobility:

•Configuring Layer 3 Mobility

•Defining the Layer 3 Peer List

•Reviewing Layer 3 Peer List Statistics

•Reviewing Layer 3 MU Status

5.5.1Configuring Layer 3 Mobility

Layer 3 mobility is a mechanism which enables a MU to maintain the same Layer 3 address while roaming throughout a multi-VLAN network. This enables transparent routing of IP datagrams to MUs during their movement, so data sessions can be initiated while they roam (in for voice applications in particular). Layer 3 mobility enables TCP/UDP sessions to be maintained in spite of roaming among different IP subnets.

A mobility domain comprises of a network of switches among which an MU can roam seamlessly without changing its IP address. Each switch in the mobility domain needs to be configured to be part of the same mobility domain (using a mobility domain string identifier) such that MUs roaming between these switches can retain their Layer 3 address and thus maintain application-layer connectivity.

When a MU enters a mobility domain by associating with a switch, it is first assigned a home switch. The home switch is responsible for assigning a VLAN for the MU and communicating the MU's mobility-related parameters to the other switches in the mobility domain. The home switch does not change for the remainder of the MU's presence in the mobility domain. All data packets transmitted/received by the MU including