What does the OSPF LSA refresh interval mean


When an OSPF link state advertisement (LSA) age reaches the link-state refresh time (1800 seconds), the OSPF updates the LSAs for advertisement.

Other related questions:
How long is the LSA refresh interval
Defined in RFC 2328, the 1800-second interval cannot be changed.

OSPF LSA update interval
On S series switches supporting OSPF, OSPF updates and advertises a generated LSA every 1800 seconds (LSA link status update interval). The interval 1800s is defined by RFC 2328 and cannot be modified.

What does the TOS field in an OSPF LSA indicate
The TOS field in an OSPF LSA was designed for QoS routing. Packets with different TOS values are transmitted on links with different cost values, enabling TOS-based routing. That is, IP packets with the same destination but different TOS values are forwarded on differentiated routes. This application, however, is canceled in RFC 2328. The OSPF devices support only TOS value 0. That is, the route is based only on destination IP address.

Set the interval at which OSPF LSAs are retransmitted on S series switches
An OSPF-enabled S series switch sends an acknowledgement packet after receiving an LSA packet. If a device does not receive any acknowledgement packet, it retransmits the LSA to its peer device. The link-state retransmit interval parameter specifies the interval at which the LSA is retransmitted. The default value is 5, in seconds. You can run the ospf timer retransmit interval command in the interface view to reset a value.

What is the LSA retransmit interval and how to set it
OSPF must send an LSAck packet after receiving a link-state advertisement (LSA). LSAs are retransmitted until they are acknowledged. The link-state retransmit interval defines the time between retransmissions. You can run the ospf timer retransmit interval command to set the retransmit interval. The default interval is 5 seconds.

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