Summarizing OSPF area 0 routes - legal or not?

[borek]

Is it possible to summarize routes (with "area range" statement) from area 0 to other areas? Karl Solie in his "CCIE Practical Studies" writes they cannot be summarized. But in Cisco documentation as well as in Bill Parkurhurst's OSPF Handbook summarization from area 0 to non-zero areas is mentioned as perfectly possible and correct.

So who is right?

[ruwhite · Accepted solution]

They can be summarized. Note here:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_command_reference_chapter09186a00800917e6.html#1017596

An example is given of summarizing into an area 10.0.0.0. And in the lab:

!

router ospf 100

log-adjacency-changes

area 0 range 208.0.6.0 255.255.254.0

network 208.0.6.0 0.0.0.255 area 0

network 208.0.7.0 0.0.0.255 area 0

network 208.0.12.0 0.0.0.255 area 1

....

2651A#sho ip ospf data summ

OSPF Router with ID (208.0.12.10) (Process ID 100)

Summary Net Link States (Area 0)

....

Summary Net Link States (Area 1)

LS age: 44

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

LS Type: Summary Links(Network)

Link State ID: 208.0.6.0 (summary Network Number)

Advertising Router: 208.0.12.10

LS Seq Number: 80000002

Checksum: 0xC7B6

Length: 28

Network Mask: /23

TOS: 0 Metric: 1

This summary is in area 1, which means that's where it's advertised.

Russ.W