Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Attention: The Community will be in read-only mode on 12/14/2017 from 12:00 am pacific to 11:30 am.

During this time you will only be able to see content. Other interactions such as posting, replying to questions, or marking content as helpful will be disabled for few hours.

We apologize for the inconvenience while we perform important updates to the Community.

OSPF LSA-Type 3 Metric Value

I've always noticd in a LSA Type-3, there is a Metric value. What exactly is that used for?

Routing Bit Set on this LSA

  LS age: 721

  Options: (No TOS-capability, DC, Upward)

  LS Type: Summary Links(Network)

  Link State ID: 10.0.0.0 (summary Network Number)

  Advertising Router: 6.6.6.6

  LS Seq Number: 80000003

  Checksum: 0xC646

  Length: 28

  Network Mask: /24

        TOS: 0  Metric: 12

I understand that from an ABR's point of view, when it advertises Type-3 LSA,s into an area, it's distance vector. Which makes sense, since all its saying is "I promise I heard about these networks", which is not a Link State protocol trait

1 ACCEPTED SOLUTION

Accepted Solutions
Silver

OSPF LSA-Type 3 Metric Value

Hi John,

metric value included in LSA3 is the distance between ABR and the destination network.

It is used by other routers in area (to which the LSA3 is flooded) to calculate the best path for that inter-area destination network.

Best path = intra-area distance from router towards ABR + distance from ABR towards destination network (metric in LSA3).

Best regards,

Jan

3 REPLIES
Silver

OSPF LSA-Type 3 Metric Value

Hi John,

metric value included in LSA3 is the distance between ABR and the destination network.

It is used by other routers in area (to which the LSA3 is flooded) to calculate the best path for that inter-area destination network.

Best path = intra-area distance from router towards ABR + distance from ABR towards destination network (metric in LSA3).

Best regards,

Jan

OSPF LSA-Type 3 Metric Value

Thanks Jan, for whatever reason I always forget that.

Silver

Re: OSPF LSA-Type 3 Metric Value

John,

you're welcome. Don't worry, me too - but from now on, whenever one of us forget it, we can find it right here .

Best regards,

Jan

287
Views
0
Helpful
3
Replies
CreatePlease to create content