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

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Impact of split OSPF leaf area

Hi,

If an OSPF leaf area becomes dis-contiguous can hosts in one half still communicate with hosts in the other half? Both halves are still connected to area 0.

TIA

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: Impact of split OSPF leaf area

Hello Graham,

without any route summarization at ABRs there is no problem if a non-zero area is partitioned until both halves are still connected to the backbone area.

if area range commands are defined on both ABRs the risk is that  from the backbone area point of view there are still two exit points for the summary route(s).

LSA type 3 are regenerated at areaa boundary and they don't have an original area-id.

So without summarization routes can be exchanged via area 0.

So ABR1 of semi-area A1 will accept LSAs generated by ABR2 of semi-area A2 and viceversa.

Between areas OSPF uses a distance vector approach.

Hope to help

Giuseppe

2 REPLIES
Hall of Fame Super Silver

Re: Impact of split OSPF leaf area

Hello Graham,

without any route summarization at ABRs there is no problem if a non-zero area is partitioned until both halves are still connected to the backbone area.

if area range commands are defined on both ABRs the risk is that  from the backbone area point of view there are still two exit points for the summary route(s).

LSA type 3 are regenerated at areaa boundary and they don't have an original area-id.

So without summarization routes can be exchanged via area 0.

So ABR1 of semi-area A1 will accept LSAs generated by ABR2 of semi-area A2 and viceversa.

Between areas OSPF uses a distance vector approach.

Hope to help

Giuseppe

New Member

Re: Impact of split OSPF leaf area

Thanks Giuseppe

612
Views
0
Helpful
2
Replies
CreatePlease to create content