This topic describes how virtual interfaces persist across active and standby route processor (RP) failover on the Cisco 8000 Series Router, and how to ensure that protocols such as TACACS+, SNMP, NTP, and syslog use the virtual IPv4 address as their source address.
The standby RP is available and in a state in which it can take over the work from the active RP should that prove necessary. Conditions that necessitate the standby RP to become the active RP and assume the active RP's duties include:
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Failure detection by a watchdog.
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Administrative command to take over.
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Removal of the active RP from the chassis.
If a second RP is not present in the chassis while the first is in operation, a second RP may be inserted and automatically becomes the standby RP. The standby RP may also be removed from the chassis with no effect on the system other than loss of RP redundancy.
After failover, the virtual interfaces are all present on the standby (now active) RP. Their state and configuration are unchanged and there is no loss of forwarding (in the case of tunnels) over the interfaces during the failover. The routers use nonstop forwarding (NSF) over bundles and tunnels through the failover of the host RP.
You do not need to configure anything to guarantee that the standby interface configurations are maintained.
Protocol configuration such as tacacs source-interface , snmp-server trap-source , ntp source , and logging source-interface does not use the virtual management IP address as its source by default. Use the ipv4 virtual address use-as-src-addr command to ensure that the protocol uses the virtual IPv4 address as its source address. Alternatively, you can configure a loopback address with the designated or desired IPv4 address and set that as the source for protocols such as TACACS+ using the tacacs source-interface command.