Articles

Video 14: OSPF Routing: Area Types and Options

In OSPF on April 25, 2011 by carlosfvc Tagged: , , , , ,

Virtual Links: breaking the rules

– The are poor design criteria and using for emergencies (bandaid)

————————-
Router 4
————————-

none

————————-
Router 3
————————

– Virtual link config (depended on router-id)

config t
router ospf 1
area 1 virtual-link 2.2.2.2

Verify

show ip ospf virtual-link

————————-
Router 2 (no area 0 direct conenction)
————————-

config t
router ospf 1
router-id 2.2.2.2
network 10.1.23.1 0.0.0.0 area 1 ( R2 to R3)
netwrok 10.1.1.1 0.0.0.0 area 2 (lan in different area)

– Virtual link config (depended on router-id)

config t
router ospf 1
area 1 virtual-link 3.3.3.3

Verify

show ip ospf virtual-link

——————–OSPF Areas and router Types

Understanding OSPF LSA Types

Link state advertisements (LSAs) are the buildinh blocks of ospf; Many types exist

LSA Type 1: Router LSA
LSA Type 2: Netwrok LSA (DR Generated)
LSA Type 3: Summany LSA (ABR Summary route)
LSA Type 4: Summary LSA (ASBR Location)
LSA Type 5: External LSA (ASBR Summay Route)

Stub and Totally Stubby Areas

Stubby area: blocks type 5 LSAs from entering

——–
Router 2
——–
config t
router ospf 1
area 2 stub

verify

sh ip route

——–
Router 1
——–

config t
router ospf 1
area 2 stub

Totally Stubby Area: Blocks type 3, 4 and 5 LSAs from entering

——–
Router 5 (only receives)
——–

config t

config t
router ospf 1
area 1 stub

——–
Router 4 (ABR) who does the filtering
——–

config t
router ospf 1
area 1 stub no-summary

Not-so-stubby areas

Passes external routes through via Type 7 LSAs; these convert back to type 5 once they reach the backbone

——–
Router 5 (ASBR)
——–

config t
router ospf 1
no area 1 stub
area 1 nssa

router ospf 1
redistribute rip subnets metric 10 *send RIP into ospf

Verify

show ip ospf data

——–
Router 4
——–

router ospf 1
area 1 nssa no-summary

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