What is the default OSPF Hello interval in which hello packets are sent out on a broadcast multi access network?
OSPF Support for Fast Hello PacketsThe OSPF Support for Fast Hello Packets feature provides a way to configure the sending of hello packets in intervals less than 1 second. Such a configuration results in faster convergence in an Open Shortest Path First (OSPF) network. Show
Finding Feature InformationYour software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table. Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required. Prerequisites for OSPF Support for Fast Hello PacketsOSPF must be already configured in the network or must be configured at the same time as the OSPF Support for Fast Hello Packets feature. Information About OSPF Support for Fast Hello PacketsOSPF Hello Interval and Dead IntervalOSPF hello packets are packets that an OSPF process sends to its OSPF neighbors to maintain connectivity with those neighbors. The hello packets are sent at a configurable interval (in seconds). The defaults are 10 seconds for an Ethernet link and 30 seconds for a non broadcast link. Hello packets include a list of all neighbors for which a hello packet has been received within the dead interval. The dead interval is also a configurable interval (in seconds), and defaults to four times the value of the hello interval. The value of all hello intervals must be the same within a network. Likewise, the value of all dead intervals must be the same within a network. These two intervals work together to maintain connectivity by indicating that the link is operational. If a router does not receive a hello packet from a neighbor within the dead interval, it will declare that neighbor to be down. OSPF Fast Hello PacketsOSPF fast hello packets refer to hello packets being sent at intervals of less than 1 second. To understand fast hello packets, you should already understand the relationship between OSPF hello packets and the dead interval. See the section OSPF Hello Interval and Dead Interval. OSPF fast hello packets are achieved by using the ip ospf dead-interval command. The dead interval is set to 1 second, and the hello-multiplier value is set to the number of hello packets you want to send during that 1 second, thus providing subsecond or "fast" hello packets. When fast hello packets are configured on the interface, the hello interval advertised in the hello packets that are sent out this interface is set to 0. The hello interval in the hello packets received over this interface is ignored. The dead interval must be consistent on a segment, whether it is set to 1 second (for fast hello packets) or set to any other value. The hello multiplier need not be the same for the entire segment as long as at least one hello packet is sent within the dead interval. Benefits of OSPF Fast Hello PacketsThe benefit of the OSPF Support for Fast Hello Packets feature is that your OSPF network will experience faster convergence time than it would without fast hello packets. This feature allows you to detect lost neighbors within 1 second. It is especially useful in LAN segments, where neighbor loss might not be detected by the Open System Interconnection (OSI) physical layer and data-link layer. How to Configure OSPF Fast Hello PacketsConfiguring OSPF Fast Hello PacketsSUMMARY STEPS
DETAILED STEPS
ExamplesThe following sample output verifies that OSPF Support for Fast Hello Packets is configured. In the line that begins with "Timer intervals configured," the hello interval is 200 milliseconds, the dead interval is 1 second, and the next hello packet is due in 76 milliseconds.
Configuration Examples for OSPF Support for Fast Hello PacketsExample OSPF Fast Hello PacketsThe following example configures OSPF fast hello packets; the dead interval is 1 second and 5 hello packets are sent every second:
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Feature Information for OSPF Support for Fast Hello PacketsThe following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature. Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
What is the default Hello interval in which OSPF Hello packets are sent out on a broadcast network?OSPF Hello Interval and Dead Interval
The hello packets are sent at a configurable interval (in seconds). The defaults are 10 seconds for an Ethernet link and 30 seconds for a non broadcast link.
How often does OSPF send hello messages?Sending & Receiving OSPF Hello Messages. An OSPF router generates a Hello packet every poll interval -10 seconds for Peer-to-Peer (P2P) networks and 30 seconds for Non-Broadcast-Multiple-Access (NBMA) networks by default- and advertises it through multicast address 224.0.
What is the OSPF default frequency in seconds at which a Cisco router sends hello packets on a multiaccess network?Hello Interval - Specifies the frequency, in seconds, at which a router sends Hello packets. The default Hello interval on multiaccess networks is 10 seconds.
How often are hello packets sent?Hello interval.
This is how often the router will send a HELLO packet on the interface to maintain adjacency. The default is 10 seconds for broadcast and point-to point networks and 30 seconds for NBMA.
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