Specifications

E-7
Cisco Internet Streamer CDS 2.0-2.3 Software Configuration Guide
OL-13493-04
Appendix E CLI Commands
Configuring Standby Interfaces
A standby group must have at least two interfaces. Interfaces that are part of a standby group are called
member interfaces. After you create a standby group, you define which interfaces should be assigned to
this logical group. As part of defining the member interfaces, you specify the priority of each member
interface in a standby group. The member interface with the highest assigned priority is the active
interface for that particular standby group. If the active interface fails, the operational member interface
with the next highest priority in the standby group comes up, and so forth. If all member interfaces of a
particular standby group are down and then one of the member interfaces comes up, the CDS software
detects this situation and brings up the standby group on the member interface that just came up.
The failure or failover of member interfaces within a standby group triggers alarms and traps (if alarms
and traps are enabled on the Service Engine). Alarms are sent out when failover occurs between member
interfaces in a standby group. Specifically, minor alarms are sent out when member interfaces fail, and
these alarms are cleared automatically when the interface failover has been successfully completed.
Major alarms are sent out if the standby group goes down (no member interface in a standby group can
be brought up).
Note A physical interface can belong to more than one standby group, and a single interface can act as a
standby interface for more than one standby group.
To configure standby interfaces, interfaces are logically assigned to standby groups. The following rules
define the standby group relationships:
• Each standby group is assigned a unique standby IP address, shared by all member interfaces of the
standby group. The IP address of the standby group is shared among the member interfaces;
however, only the active interface of the standby group uses this shared IP address at any one time.
This shared IP address is configured as an alias on the active interface.
• The duplex and speed settings of the member interfaces can be configured for better reliability.
• If a physical interface is a member of a port-channel group, it cannot join a standby group. If a
physical interface is a member of a standby group, it cannot join a port-channel group.
• The maximum number of standby groups on a Service Engine is four.
Note Interface IP addresses and standby group IP addresses must be on different subnets to ensure reliable
operation. You can use dummy IP addresses in the private address space to serve as interface primary IP
addresses, and use the real Service Engine IP address to serve as the standby group IP address in a
different subnet to satisfy this requirement. When dummy IP addresses are used, these interface IP
addresses serve only as substitutes to bring up the interface. For example, the Service Engine interface
requires an IP address on an interface for initialization. Make sure to configure the interface default
gateway using the ip default-gateway global configuration command instead of the ip route command.
• Each interface in a standby group is assigned a priority. The operational interface with the highest
priority in a standby group is the active interface. Only the active interface uses the group IP address.
• The priority of an interface in a standby group can be changed at run time. The member interface
that has the highest priority after this change becomes the new active interface (the default action is
to preempt the currently active interface if an interface with higher priority exists).
• The maximum number of errors allowed on the active interface before the interface is shut down and
the standby is brought up is configured with the errors option, which is disabled by default.