Last week we raised some OSPF questions, and let’s continue this week.
First I ask a question with stub area.
Question 1:
R1 have an loopback0 1.1.1.1/32, network in area 1, R5 also belong area 1 and connect to R4,
R3 have an loopback0 3.3.3.3/32, network in area 0,
The number on the topology is the link cost
area 1 is a stub area, area 0 is backbone area
R2 have command: area 1 stub
R4 have command: area 1 stub no-summary
I. R5 have LSA-3 and route about R3 lo0 3.3.3.3 or not? Why?
II. R5 access R3 lo0 3.3.3.3, use which path, path1 or path2? And why?
As we know, OSPF send LSAs not routes, so if you want filter some detail routes in OSPF (except just effect local device), you need use some commands filter LSA. We have 6 methods for filter:
i.distribute-list
ii.area range x.x.x.x x.x.x.x not-advertise
iii.summary-address x.x.x.x x.x.x.x not-advertise
iv.area X filter-list prefix 1 {in | out}
v.if# ip ospf database-filter all out
vi.neighbor x.x.x.x database-filter all out
Every method used in diff case, recently have another method used for filter LSA-1 direct-link prefixes.
Question 2:
My question is: ‘summary-address x.x.x.x x.x.x.x not-advertise’
This command used for filter LSA-5, actually when LSA-5 can be generate?
When use redistribute command on Router or other way? what is other way? If you interesting, you can answer it.
If you want filter LSA-5, you can use ‘redistribute’ + ‘route-map’, right? So when we need use ‘summary-address x.x.x.x x.x.x.x not-advertise’.
OK, just 2 questions, more questions will show you next time, if you interested, type your answer below.
Have fun!!!
By lecturer James
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