OSPF database drops some links instantly, others an hour later
Here's a thing (ok, two things) I didn't expect. I wanted to experiment with manual OSPF summarization; so I created a bunch of loopbacks on Router A (internal in Area 1) and routed them into OSPF.
Happily, they appeared in Router J's (internal in Area 2) table, as well as in its ospf database (naturall). All was well.
The first mistake I made was to configure the "area 1 range" command on Router A, which isn't an ABR. Router F is ABR for Area 1; so I wa surprised the IOS allowed me to configure the area range command in the first place.
I removed it from Router A and entered it on Router F.
The summary route appeared in J's routing table, as I expected. What surprised me was that all the specific links that had been summarized had also vanished from J's ospf database.
I thought entries weren't supposed to leave the database until they've been dead for an hour. I've brought down links physically yes PHYSICALLY in ospf networks, and while they always leave the routing table promptly, they have remained in the ospf database for hour.
So why did the specific (30-bit) networks get purged immediately when the summary (28-bit) network showed up? What's the reasoning behind holding on to an LSA for an hour after the link is known dead, but flushing a specific LSA when an inclusive summary arrives?
The former isn't in line with the goal of keeping the database lean. And I'm not sure that the latter is in line with keeping the database thorough.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.