OSPF design

gauravprakash · ‎12-07-2009

Following is the OSPF network..

r1-----r2------r3
|                  |
|                  |
|                  |
|                  |
r4..............r5
.                .
.                .
.                .
r6             r7

R4 & R5 are the ABRs for XYZ.
Link connecting (r5 & r4), (r4 & r6), (r5 & r7) are in Area 0(backbone)
Links connecting r4-r1, r1-r2, r2-r3, r3-r5 are in Area XYZ

Do we need any virtual link?
Are there any specific issue if we consider Loadbalancing based on OSPF or run MPLS TE..?

Thx,

GP

Jon Marshall · ‎12-07-2009

gauravprakash wrote:

Following is the OSPF network..

r1-----r2------r3
|                  |
|                  |
|                  |
|                  |
r4..............r5
.                .
.                .
.                .
r6             r7

R4 & R5 are the ABRs for XYZ.
Link connecting (r5 & r4), (r4 & r6), (r5 & r7) are in Area 0(backbone)
Links connecting r4-r1, r1-r2, r2-r3, r3-r5 are in Area XYZ

Do we need any virtual link?
Are there any specific issue if we consider Loadbalancing based on OSPF or run MPLS TE..?

Thx,

GP

No you don't need a virtual link as area XYZ connects to area 0.

This should load balance fine over the 2 links.

Not sure what you mean as reagrds MPLS-TE ?

Jon

Giuseppe Larosa · ‎12-07-2009

Hello Gaurav,

I would add a link in area0 or you would need a virtual link to protect area 0 partitioning, that would happen if the link between the two ABRs (R4 ans R5) fails.

virtual-link are not recommended in real world networks.

Also the link between R4 and R5 can be logically divided into two logical links one in area 0 one in area XYZ.

with modern multilayer switches this is simple and efficient.

about MPLS TE now it should be possible to have it on multiple areas but at the beginning all MPLS TE has been confined in a single area.

load balancing from the point of view of R2 is possible as noted by Jon.

Hope to help

Giuseppe

gauravprakash · ‎12-09-2009

Thx..

So.. in my case as link between r4--r5 is already in Area 0, I need to add another link ( logical subinterface or physical ) between r4 and r5 and put it in Area XYZ.

Right ?

If I dont do the above , there may be a chance of Area XYZ spliting into two incase of link r1--r2 or r2---r3 failur.

Am I right now..

Thx again

Gaurav

Giuseppe Larosa · ‎12-10-2009

Hello Gaurav,

actually also area 0 is exposed to the same risk so you should add a physical link or between R4 and R5 or between the other two routers with links in area 0.

I'm more worried for a partition of backbone area then that of a standard area like area XYZ.

Hope to help

Giuseppe