35-27
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 35 Configuring IP Unicast Routing
Configuring OSPF
OSPF Nonstop Forwarding
The switch stack supports two levels of nonstop forwarding (NSF):
• OSPF NSF Awareness, page 35-27
• OSPF NSF Capability, page 35-27
OSPF NSF Awareness
Beginning with Cisco IOS Release 12.2(25)SE, the IP services image supports OSPF NSF Awareness
for IPv4. When a neighboring router is NSF-capable, the Layer 3 switch continues to forward packets
from the router before the backup Route Processor (RP) in a router takes over after the primary RP fails,
or while the primary RP is manually reloaded for a nondisruptive software upgrade.
This feature cannot be disabled. For more information on this feature, see the OSPF Nonstop Forwarding
(NSF) Awareness Feature Guide at this URL:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_white_paper09186a0080153edd.s
html
OSPF NSF Capability
Beginning with Cisco IOS Release 12.2(35)SE, the IP services image 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.
Router ID No OSPF routing process defined.
Summary address Disabled.
Timers LSA group pacing 240 seconds.
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 3550, 3560 and 3750 switches running the IP services image, Cisco
IOS Release 12.2(25)SEC or later.
Table 35-5 Default OSPF Configuration (continued)
Feature Default Setting