OSPF Commands

Question 1

Filter out a route from being advertised outside the area where it originates but allow local routers to still see it.

Answer 1

area 1 range 172.16.2.0 255.255.255.0 not-advertise

Question 2

Summarize routes as they are crossing an OSPF ABR

Answer 2

area range [advertise|not-advertise] [cost]
router ospf 1
area 2 range 172.16.0.0 255.255.0.0

Question 3

Filter routes as they are crossing an OSPF ABR

Answer 3

area filter-list prefix {in | out}

ip prefix-list PREFIX-FILTER seq 5 deny 172.16.1.0/24
ip prefix-list PREFIX-FILTER seq 10 permit 0.0.0.0/0 le 32
router ospf 1
area 0 filter-list prefix PREFIX-FILTER in

Question 4

Filter OSPF routes from entering the RIB

Answer 4

ip access-list standard ACL-OSPF-FILTER
deny 172.16.3.0
permit any
exit

router ospf 1
distribute-list ACL-OSPF-FILTER in

Question 5

Advertise a default route into OSPF

Answer 5

default-information originate [always] [metric <metric-value>] [metric-type <type-value>]</type-value></metric-value>

ip route 0.0.0.0 0.0.0.0 100.64.1.2
router ospf 1
default-information originate

Question 6

Modify the OSPF reference bandwidth for dynamic interface metric costing

Answer 6

auto-cost reference-bandwidth <bandwidth_in_mbps></bandwidth_in_mbps>

router ospf 1
auto-cost reference-bandwidth 40000

(sets reference bandwidth to 40 Gig)

Question 7

Statically set the OSPF metric for an interface

Answer 7

interface gig0/1
ip ospf cost <1–65535>

Question 8

Configure the OSPF priority for a DR/BDR election

Answer 8

interface gig0/1
ip ospf priority <0–255>

Question 9

Show the reference bandwidth

Answer 9

‘show ip ospf | i Reference