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Persistence
The persistence feature allows information learned through DHCP snooping across reboots to be
kept. This information can include data such as the IP address, MAC binding information, lease-
length information, and ingress sap information (required for VPLS snooping to identify the
ingress interface). This information is referred to as the DHCP lease-state information.
When a DHCP message is snooped, there are steps that make the data persistent in a system with
dual CFMs. In systems with only one CFM, only Step 1 applies. In systems with dual CFMs, all
steps apply.
1. When a DHCP ACK is received from a DHCP server, the entry information is written to the
active CFM Compact Flash. If writing was successful, the ACK is forwarded to the DHCP
client. If persistency fails completely (bad cflash), a trap is generated indicating that persis-
tency can no longer be guaranteed. If the complete persistency system fails the DHCP
ACKs are still forwarded to the DHCP clients. Only during small persistency interruptions or
in overload conditions of the Compact Flash, DHCP ACKs may get dropped and not for-
warded to the DHCP clients.
2. DHCP message information is sent to the standby CFM and also there the DHCP informa-
tion is logged on the Compact Flash. If persistency fails on the standby also, a trap is gener-
ated.
System-Wide ATM Parameters
The atm-ping OAM loopback feature can be enabled on an ATM SAP for a period of time
configured through the interval and the send-count parameters. When the ATM SAP terminates on
IES or VPRN services, a failure of the loopback state machine does not bring down the Layer 3
interface. Only receiving AIS/RDI OAM cells or entering the AIS/RDI state brings down the
Layer 3 interface.
The atm-ping OAM loopback feature can be also be enabled on a continuous basis on an ATM
SAP terminating on IES or VPRN services. When the loopback state machine fails, the Layer 3
interface is brought down.
The ATM OAM loopback parameters must be first enabled and configured in the config>system>
atm>oam context and then enabled in the
context.
Rerfer to the IES and VPRN sections of the 7710 SR OS Services Guide for further information.
7710 SR OS Basic System Configuration Guide
IES or VPRN service interface SAP atm oam
System Management
Page 203
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