DR Site - Help with OSPF

Unanswered Question
Nov 10th, 2007


I need to put together a proposal for DR. We are currently routing between sites 1, 2, 3, 4 with EIGRP, but I want to change to OSPF and add the DR site and Site 5 to OSPF.

At main Site 1, I want to do equal cost paths to the internet and split some of the load.

I'm just not 100% sure on how to config OSPF between all sites and have them redundant. Net. topology is attached.

thanks for your help!

I have this problem too.
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bvsnarayana03 Sat, 11/10/2007 - 06:54

At site 1, the 2 internet links are of unequal capacity & diference in BW is also more. If u do load-balancing, 1Mbps may be choked throughout the day whereas 5Mbps may not have much on it. It is better to use the 2 links in active /backup configuration using either static routes with AD in case of single ISP, or BGP if multihoming.

However on intranet, configure ospf on all routers with bandwidths as mentioned in diagram. Routing will be taken care by ospf itself. But sites 4 & 5 are a real concern bcoz they dont have a backup to DR. So in case Pri site 1 goes down, sites 4 & 5 will be isolated. I assume they are not so important sites.

There is one concern here. If u run EIGRP & OSPF simultaneously, Eigrp wins by AD & will do all routing. So AD may have to be changed for migration to have OSPF as primary routing protocol.

opers13 Sun, 11/11/2007 - 04:26

bvsnarayana03, thanks.

Yes, sites 4 and 5 are not important. We would route OSPF only, EIGRP would be gone.

Should I make all sites a single area or split into 2 or more areas?

bvsnarayana03 Sun, 11/11/2007 - 07:13

OSPF is a link state protocol which means every time there is fluctuation in link, there will be change in routes associated with it & these changes will be propagated throughtout the area.This would put burden on router resources viz cpu & mem. So larger the changes, higher the utilisation.

Thus it is basically for u to decide. How many networks will be in ospf, how many links, will there be any redistribution (if yes then how many networks). Is there an expected growth in future. All these factors play an important role in deciding for area configs.


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