[j-nsp] ospf area-range summary lsa-id changes between areas

[Aaron Gould]

Hi, in Harry Reynolds JNCIP Book, page 202 of 708 is the ospf multi-area
picture.   page 217 of 708 mentions summarization using area-range.

 

Is there a reason why the lsa-id in area 0 is 10.0.8.0 but is 10.0.9.255 in
area 10 ?  It's interesting that the subnet-id of the /23 is used as the
lsa-id in area 0 but the bcast address of the /23 is used as the lsa-id in
area 10.

 

Is there a technical reason for the change in lsa-id as that summary flows
through ospf areas?

 

When I do this on r5.

 

r5 at lab-mx104:r5# set protocols ospf area 1 area-range 10.0.8.0/23

 

.I see this on r3..

 

r3 at lab-mx104:r3> show ospf database area 0 netsummary lsa-id 10.0.8.0 detail

 

    OSPF database, Area 0.0.0.0

Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len

Summary  10.0.8.0         10.0.3.5         0x80000471   934  0x22 0x4360  28

  mask 255.255.254.0

  Topology default (ID 0) -> Metric: 2

 

.but I see this on r1..

 

r1 at lab-mx104:r1> show ospf database netsummary area 10 lsa-id 10.0.9.255
detail

 

    OSPF database, Area 0.0.0.10

Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len

Summary  10.0.9.255       10.0.3.3         0x80000001   967  0x20 0x59c0  28

  mask 255.255.254.0

  Topology default (ID 0) -> Metric: 3

Summary  10.0.9.255       10.0.3.4         0x80000001   968  0x20 0x53c5  28

  mask 255.255.254.0

  Topology default (ID 0) -> Metric: 3

 

r1 at lab-mx104:r1>

 

JNCIP Book.

https://www.juniper.net/assets/us/en/local/pdf/study-guide/study-guide-jncip
.pdf

 

Thanks,
Aaron