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Community Member

OSPF (ASBR)

I read from the book that ASBR is used to join different routing domain.

However, i notice that there is a router in my company used only ospf but receive LSA Type 1, 2, 3,4 and 5 (External) in the database.

However this router is consider ASBR when i issue "Show ip protocols"

What is the theory behind? Or can i say if the router is receiving LSA type 5, it is consider a ASBR router. I am confusing now. Thanks!

4 REPLIES
Hall of Fame Super Gold

Re: OSPF (ASBR)

Kianhong

Receiving LSA type 5 does not qualify a router as an ASBR. An ASBR generates type 5 LSA and not receives them.

Perhaps it would help us to understand the situation and to give you better answers if you would post the output of show ip ospf and of show ip protocol from that router.

HTH

Rick

Community Member

Re: OSPF (ASBR)

A5# sh ip protocols

Routing Protocol is "ospf 1"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Router ID 172.16.20.10

It is an autonomous system boundary router

Redistributing External Routes from,

connected, includes subnets in redistribution

static, includes subnets in redistribution

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Address Summarization:

Maximum path: 4

Routing for Networks:

10.152.0.0 0.0.3.255 area 0

Reference bandwidth unit is 100 mbps

Passive Interface(s):

Vlan30

Routing Information Sources:

Gateway Distance Last Update

10.1.3.8 110 2w4d

10.1.2.9 110 3w5d

10.1.2.3 110 3w5d

10.1.3.3 110 3w5d

10.1.3.5 110 2w4d

10.1.3.6 110 2w4d

10.1.3.7 110 2w4d

1.1.1.17 110 22:00:15

172.16.20.10 110 6w3d

166.xx.xx.x 110 21:56:12

Distance: (default is 110)

A5#sh ip ospf

Routing Process "ospf 1" with ID 172.16.20.10

Start time: 12w4d, Time elapsed: 29w0d

Supports only single TOS(TOS0) routes

Supports opaque LSA

Supports Link-local Signaling (LLS)

Supports area transit capability

It is an autonomous system boundary router

Redistributing External Routes from,

connected, includes subnets in redistribution

static, includes subnets in redistribution

Router is not originating router-LSAs with maximum metric

Initial SPF schedule delay 5000 msecs

Minimum hold time between two consecutive SPFs 10000 msecs

Maximum wait time between two consecutive SPFs 10000 msecs

Incremental-SPF disabled

Minimum LSA interval 5 secs

Minimum LSA arrival 1000 msecs

LSA group pacing timer 240 secs

Interface flood pacing timer 33 msecs

Retransmission pacing timer 66 msecs

Number of external LSA 563. Checksum Sum 0x57CA8E3

Number of opaque AS LSA 0. Checksum Sum 0x000000

Number of DCbitless external and opaque AS LSA 7

Number of DoNotAge external and opaque AS LSA 0

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Number of areas transit capable is 0

External flood list length 0

IETF NSF helper support enabled

Cisco NSF helper support enabled

Area BACKBONE(0)

Number of interfaces in this area is 2

Area has no authentication

SPF algorithm last executed 21:55:21.744 ago

SPF algorithm executed 354 times

Area ranges are

Number of LSA 16. Checksum Sum 0x232DA0

Number of opaque link LSA 0. Checksum Sum 0x000000

Number of DCbitless LSA 3

Number of indication LSA 0

Number of DoNotAge LSA 0

Flood list length 0

Community Member

Re: OSPF (ASBR)

Hi Kianhong,

Following the information that you have recently posted , you are redistributing the static and connected routes into OSPF via this router. Because you are injecting the connected and static routes which are currently not within the OSPF domain ( some connected interfaces might be included in OSPF domain by enabling OSPF on them but static routes are not included ), you are injecting new routes to OSPF. This process is just like redistributing from another routing protocol domain, so the router acts like an ABSR and indicates its position on the outputs .

HTH,

Kerem

Silver

Re: OSPF (ASBR)

kian

kindly check under ospf process, you are deifnately using the redistribute static.

regards

shivlu jain

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