ICND2 - Link State Periodic Updates - Periodic Update versus Reflooding???

Node Man

Hi Everyone,
I am going to get very specific for this question because Odom is confusing me. On page 352, in the chart, it says OSPF and EIGRP do not send periodic updates, however in a paragraph on page 371, it clearly says that OSPF 'refloods' every 30 minutes (RIP sends every 30 seconds).

So, is reflooding different than a periodic update?

Please help.

Thanks!

theodoxa

In the [CCNP] ROUTE FLG, it says that link-state protocols send a "Link-State Refresh" at long intervals, such as 30 minutes. That was on page 186, which is in the OSPF Chapter, so I assume they are referring to OSPF in the 30 minute example. The only other Link-State protocol they mention is IS-IS and only in passing.

OSPF: Frequently Asked Questions - Cisco Systems

Q. How often does OSPF send out link-state advertisements (LSAs)?

A. OSPF sends out its self-originated LSAs when the LSA age reaches the link-state refresh time, which is 1800 seconds. For more information, refer to Link-State Advertisements.

powmia

The wording is key. The reflooding is not "updates."

When a new route is added to a RIP domain, RIP routers wait until the next periodic advertisement to add the new routes. With EIGRP, OSPF, and IS-IS, when a new route that is added, it is immediately sent to neighbors. This is the reason that these protocols establish neighbors, while RIP does not.

The periodic refreshing of LSAs/LSPs in OSPF and IS-IS is not an "update" to the link-state database. It is a complete resynchronization to ensure no information had been corrupted in the last 30 minutes or whatever it's set to.