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    Recommended Settings for Routing Protocol Timers During Unified ISSU

    You can use the default values for many of the routing protocol timers with no adverse effect on a unified in-service software upgrade. For other timers, we recommend particular values, as described in Table 1.

    Table 1: Recommended Routing Protocol Timer Settings

    Protocol

    Timers

    BFD

    Use the default timers.

    BGP

    Use the default timers, including graceful restart default timers. If the expected forwarding outage for the platform is beyond what the BGP session’s graceful restart mechanism can survive, the unified ISSU initialization process generates a warning message accordingly. In this event, adjust the timer intervals as advised by the message.

    For information about the expected forwarding outage, see Interruption in Traffic Forwarding for Layer 3 Routing Protocols During Unified ISSU.

    The keepalive and hold timers for BGP IPv6 address families should be configured as follows:

    • On E120 and E320 routers, the keepalive timer should be set as 30 seconds and the hold timer should be set as 90 seconds.
    • On ERX1440 routers, the keepalive timer should be set as 70 seconds and the hold timer should be set as 210 seconds.

    DVMRP

    Use the default timers.

    IGMP

    Use the default timers.

    IS-IS

    Use the default timers, including graceful restart default timers.

    LDP

    Use the default timers, including graceful restart default timers, except for the following:

    • Set the hello hold time to at least 901 seconds for a helper or a restarter configuration for a link-level adjacency or for LDP targeted sessions.

    OSPF

    Use the default timers, including graceful restart default timers, except for the dead interval.

    If the expected forwarding outage for the platform is longer than the configured dead interval, the unified ISSU initialization process generates a warning message accordingly. In this event, adjust the timer interval as advised by the message.

    For information about the expected forwarding outage, see Interruption in Traffic Forwarding for Layer 3 Routing Protocols During Unified ISSU.

    PIM

    Set the query interval to at least 210 seconds.

    Unified ISSU generates a warning for any of the following conditions, but you can ignore the warning without causing a higher FC outage:

    • The current router is a DR.
    • The current router is configured as an Auto RP mapping agent and is chosen as the RP for any group.
    • The current router is an elected or candidate BSR, or if BSR candidate RPs are configured.
    • The graceful restart timer is less than the default value, 30 seconds.

    RIP

    Use the default timers; graceful restart is not supported. For scaled configurations, such as for 2000 RIP interfaces, use the following values:

    • Flush interval: 600 seconds
    • Holddown time: 260 seconds
    • Invalid interval: 260 seconds
    • Update interval: 60 seconds

    RSVP-TE

    Use the default timers, including graceful restart default timers, except for the following:

    • For graceful restart, the hello timeout interval is the product of hello misses multiplied by the hello refresh interval. Determine which period is longer, the IC upgrade time or the forwarding upgrade time. Configure the hello refresh and hello miss values so that the hello timeout is greater than the longer of those two periods.
    • For node hellos, the product of the refresh misses multiplied by the hello refresh interval must be great than the FC outage time. For an outage time of less than 30 seconds, for example, configure the following values:
      • Set the node hello refresh interval to 8000.
      • Set the node hello refresh misses to 4.
     
     

    Published: 2014-08-12