Managing Serviceguard Seventeenth Edition, First Reprint December 2009

• actively keep track of which neighbors are reachable, and which are not, and detect
changed link-layer addresses.
• search for alternate functioning routers when the path to a router fails.
Within the Ethernet family, local switching is supported in the following configurations:
• 1000Base-SX and 1000Base-T
• 1000Base-T or 1000BaseSX and 100Base-T
On HP-UX 11i, however, Jumbo Frames can only be used when the 1000Base-T or
1000Base-SX cards are configured. The 100Base-T and 10Base-T cards do not support
Jumbo Frames. Additionally, network interface cards running 1000Base-T or 1000Base-SX
cannot do local failover to 10BaseT.
During the transfer, IP packets will be lost, but TCP (Transmission Control Protocol)
will retransmit the packets. In the case of UDP (User Datagram Protocol), the packets
will not be retransmitted automatically by the protocol. However, since UDP is an
unreliable service, UDP applications should be prepared to handle the case of lost
network packets and recover appropriately. Note that a local switchover is supported
only between two LANs of the same type. For example, a local switchover between
Ethernet and IPoIB interfaces is not supported, but a local switchover between 10BT
Ethernet and 100BT Ethernet is supported.
Figure 3-16 shows two nodes connected in one bridged net. LAN segments 1 and 2 are
connected by a hub.
Figure 3-16 Cluster Before Local Network Switching
Node 1 and Node 2 are communicating over LAN segment 2. LAN segment 1 is a
standby.
94 Understanding Serviceguard Software Components