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42-28
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 42 Configuring IP Unicast Routing
Configuring OSPF
OSPF Nonstop Forwarding
The switch or switch stack supports two levels of nonstop forwarding (NSF):
• OSPF NSF Awareness, page 42-28
• OSPF NSF Capability, page 42-28
OSPF NSF Awareness
The IP-services feature set supports OSPF NSF Awareness supported for IPv4. When the neighboring
router is NSF-capable, the Layer 3 switch continues to forward packets from the neighboring router
during the interval between the primary Route Processor (RP) in a router crashing and the backup RP
taking over, or while the primary RP is manually reloaded for a non-disruptive software upgrade.
This feature cannot be disabled. For more information on this feature
, see the “OSPF Nonstop
Forwarding (NSF) Awareness” section of the Cisco IOS IP Routing Protocols Configuration Guide,
Release 12.4 at this URL:
http://www.cisco.com/en/US/products/ps6350/products_
configuration_guide_chapter09186a00804557
a8.html
OSPF NSF Capability
The IP-services feature set also supports OSPF NSF-capable routing for IPv4 for better convergence and
lower traffic loss following a stack master change. When a stack master change occurs in an OSPF
NSF-capable stack, the new stack master must do two things to resynchronize its link-state database with
its OSFP neighbors:
• Release the available OSPF neighbors on the network without resetting the neighbor relationship.
• Reacquire the contents of the link-state database for the network.
After a stack master change, the new master sends an OSPF NSF si
gnal to neighboring NSF-aware
devices. A device recognizes this signal to mean that it should not reset the neighbor relationship with
the stack. As the NSF-capable stack master receives signals from other routes on the network, it begins
to rebuild its neighbor list.
Timers shortest path first (spf) spf delay: 5 seconds.; spf-holdtime: 10 seconds.
Virtual link No area ID or router ID defined.
Hello interval: 10 seconds.
Retransmit interval: 5 seconds.
Transmit delay: 1 second.
Dead interval: 40 seconds.
Authentication key: no key predefined.
Message-digest key (MD5): no key predefined.
1. NSF = Nonstop forwarding
2. OSPF NSF awareness is enabled for IPv4 on Catalyst 3750-E and 3560-E switches running the IP services feature set.
Table 42-5 Default OSPF Configuration (continued)
Feature Default Setting