Im using OSPF to distribute MPLS trough a network.
To do this - i have Connected a bounch of routeres using x.x.x.x/29 to Connect R1 to R2 - and having a loopback to all routeres. I enable MPLS to all Interfaces linking routers together. All "ok".
I have ospf to distribute MPLS labels - also working all ok. Today i see an unknown error - having impact to all Devices.
Lets say i have 100 routers connecting one or another way. Some are Connected to make a "ring" infrastructute. With "spikes". No router should have a static deafult GW - but all is configuerd to have a default gw in ospf - if installed.
All ok. - it seems.
But now - i have started to have som flapping in OSPF. In my mind - OSPF - should alway choose shortest path.......... - But now .- it has started to flap between Main path (shortest) - and backup (none shortest).
Why does this flap ocure? and is this a bug?
for about 10 secound - my R1 have R2 as GW - using ospf over Interface X that link em together. R3 have a link to core - but have a opf cost by about 1500. R1-R2 - say 110 in cost.
Now this two links habe started to "flapping" - say . DO 0.0.0.0 by Interface 1 (cost 110) for some secound - and then - DO - by interface2 (cost 1000 (and something) for some sec - then back to Interface 1.
Why does this happen? Shopuld it not choose the chortest path? and then "stuck" to this? - Why does it "flapping" ?