Managing Serviceguard 14th Edition, June 2007

Understanding Serviceguard Software Components
How the Network Manager Works
Chapter 3106
Remote Switching
A remote switch (that is, a package switch) involves moving packages
and their associated IP addresses to a new system. The new system must
already have the same subnetwork configured and working properly,
otherwise the packages will not be started. With remote switching, TCP
connections are lost. TCP applications must reconnect to regain
connectivity; this is not handled automatically. Note that if the package
is dependent on multiple subnetworks, all subnetworks must be
available on the target node before the package will be started.
Note that remote switching is supported only between LANs of the same
type. For example, a remote switchover between an Ethernet interface on
one machine and an IPoIB interface on the failover machine is not
supported. The remote switching of relocatable IP addresses is shown in
Figure 3-5 and Figure 3-6.
Address Resolution Messages after Switching
When a floating IPv4 address is moved to a new interface, either locally
or remotely, an ARP message is broadcast to indicate the new mapping
between IP address and link layer address. An ARP message is sent for
each IPv4 address that has been moved. All systems receiving the
broadcast should update the associated ARP cache entry to reflect the
change. Currently, the ARP messages are sent at the time the IP address
is added to the new system. An ARP message is sent in the form of an
ARP request. The sender and receiver protocol address fields of the ARP
request message are both set to the same floating IP address. This
ensures that nodes receiving the message will not send replies.
Unlike IPv4, IPv6 addresses use NDP messages to determine the
link-layer addresses of its neighbors.
Automatic Port Aggregation
Serviceguard supports the use of automatic port aggregation through
HP-APA (Auto-Port Aggregation, HP product J4240AA). HP-APA is a
networking technology that aggregates multiple physical Fast Ethernet
or multiple physical Gigabit Ethernet ports into a logical link aggregate.
HP-APA allows a flexible, scalable bandwidth based on multiple 100
Mbps Fast Ethernet links or multiple 1 Gbps Ethernet links (or 200
Mbps and 2 Gbps full duplex respectively). Its other benefits include load
balancing between physical links, automatic fault detection, and