drop-count consecutive-failures
no drop-count
config>vrrp>priority-event>host-unreachable
Supported on all 7210 SAS platforms as described in this document
This command configures the number of consecutively sent ICMP echo request messages that must fail before the host unreachable priority control event is set.
The drop-count command is used to define the number of consecutive message send attempts that must fail for the host-unreachable priority event to enter the set state. Each unsuccessful attempt increments the event consecutive message drop counter. With each successful attempt, the event consecutive message drop counter resets to zero.
If the event consecutive message drop counter reaches the drop-count value, the host-unreachable priority event enters the set state.
The event hold-set value defines how long the event must stay in the set state even when a successful message attempt clears the consecutive drop counter. The event is not cleared until the consecutive drop counter is less than the drop-count value and the hold-set timer has a value of zero (expired).
The no form of this command reverts to the default value.
3
Specifies the number of ICMP echo request message attempts that must fail for the event to enter the set state. It also defines the threshold so a lower consecutive number of failures can clear the event state.
[no] host-unreachable ip-address
config>vrrp>policy>priority-event
Supported on all 7210 SAS platforms as described in this document
This command configures a host unreachable priority control event to monitor the ability to receive ICMP echo reply packets from an IP host address.
A host unreachable priority event creates a continuous ICMP echo request (ping) probe to the specified ip-address. If a ping fails, the event is considered to be set. If a ping is successful, the event is considered to be cleared.
Multiple unique (different ip-address) host-unreachable event nodes can be configured within the priority-event node, to a maximum of 32 events.
The host-unreachable command can reference any valid local or remote IP address. The ability to ARP a local IP address or find a remote IP address within a route prefix in the route table is considered part of the monitoring procedure. The host-unreachable priority event operational state tracks ARP or route table entries dynamically appearing and disappearing from the system. The following table lists the possible operational states of the host-unreachable event.
| Host unreachable operational state | Description |
|---|---|
Set – no ARP |
No ARP address found for ip-address for drop-count consecutive attempts. Only applies when IP address is considered local. |
Set – no route |
No route exists for ip-address for drop-count consecutive attempts. Only applies when IP address is considered remote. |
Set – host unreachable |
ICMP host unreachable message received for drop-count consecutive attempts. |
Set – no reply |
ICMP echo request timed out for drop-count consecutive attempts. |
Set – reply received |
Last ICMP echo request attempt received an echo reply but historically not able to clear the event. |
Cleared – no ARP |
No ARP address found for ip-address - not enough failed attempts to set the event. |
Cleared – no route |
No route exists for ip-address - not enough failed attempts to set the event. |
Cleared – host unreachable |
ICMP host unreachable message received - not enough failed attempts to set the event. |
Cleared – no reply |
ICMP echo request timed out - not enough failed attempts to set the event. |
Cleared – reply received |
Event is cleared - last ICMP echo request received an echo reply. |
Unlike other priority event types, the host-unreachable priority event monitors a repetitive task. A historical evaluation is performed on the success rate of receiving ICMP echo reply messages. The operational state takes its cleared and set orientation from the historical success rate. The informational portion of the operational state is derived from the result of the last attempt. It is possible for the previous attempt to fail while the operational state is still cleared due to an insufficient number of failures to cause it to become set. It is also possible for the state to be set while the previous attempt was successful.
When an event transitions from clear to set, the set is processed immediately and must be reflected in the associated virtual router instances in-use priority value. As the event transitions from clear to set, a hold-set timer is loaded with the value configured by the events hold-set command. This timer prevents the event from clearing until it expires, damping the effect of event flapping. If the event clears and becomes set again before the hold-set timer expires, the timer is reset to the hold-set value, extending the time before another clear can take effect.
The hold-set timer must be expired and the historical success rate must be met before the event operational state becoming cleared.
The no form of this command deletes the specific IP host monitoring event. The event may be deleted at anytime. When the event is deleted, the in-use priority of all associated virtual router instances must be reevaluated. The event hold-set timer has no effect on the removal procedure.
no host-unreachable
Specifies the IP address of the host for which the specific event will monitor connectivity. The ip-address can only be monitored by a single event in this policy. The IP address can be monitored by multiple VRRP priority control policies. The IP address can be used in one or multiple ping requests. Each VRRP priority control host-unreachable and ping destined to the same ip-addr is uniquely identified on a per message basis. Each session originates a unique identifier value for the ICMP echo request messages it generates. This allows received ICMP echo reply messages to be directed to the appropriate sending application.
interval seconds
no interval
config>vrrp>priority-event>host-unreachable
Supported on all 7210 SAS platforms as described in this document
This command configures the number of seconds between host unreachable priority event ICMP echo request messages directed to the host IP address.
The no form of this command reverts to the default value.
1
Specifies the number of seconds between the ICMP echo request messages sent to the host IP address for the host unreachable priority event.
timeout seconds
no timeout
config>vrrp>priority-event>host-unreachable
Supported on all 7210 SAS platforms as described in this document
This command defines the time, in seconds, that must pass before considering the far-end IP host unresponsive to an outstanding ICMP echo request message.
The timeout value is not directly related to the configured interval parameter. The timeout value may be larger, equal, or smaller, relative to the interval value.
If the timeout value is larger than the interval value, multiple ICMP echo request messages may be outstanding. Every ICMP echo request message transmitted to the far end host is tracked individually according to the message identifier and sequence number.
With each consecutive attempt to send an ICMP echo request message, the timeout timer is loaded with the timeout value. The timer decrements until one of the following occurs.
An internal error occurs preventing message sending (request unsuccessful).
An internal error occurs preventing message reply receiving (request unsuccessful).
A required route table entry does not exist to reach the IP address (request unsuccessful).
A required ARP entry does not exist and ARP request timed out (request unsuccessful).
A valid reply is received (request successful).
It is possible for a required ARP request to succeed or timeout after the message timeout timer expires. In this case, the message request is unsuccessful.
If an ICMP echo reply message is not received before the timeout period for a specific ICMP echo request, that request is considered to be dropped and increments the consecutive message drop counter for the priority event.
If an ICMP echo reply message with the same sequence number as an outstanding ICMP echo request message is received before that message timing out, the request is considered successful. The consecutive message drop counter is cleared and the request message no longer is outstanding.
If an ICMP Echo Reply message with a sequence number equal to an ICMP echo request sequence number that had previously timed out is received, that reply is silently discarded while incrementing the priority event reply discard counter.
The no form of this command reverts to the default value.
1
Specifies the number of seconds before an ICMP echo request message is timed out. When a message is timed out, a reply with the same identifier and sequence number is discarded.