fmatrine
join:2005-08-08
400603
| [Config] ISDN Multisite dialup using OSPF cost issue
Hi All,
Need Assistance for setting up the
Pls refer attached topology, and Router configuration for Central site (Datacentre) routers, DR Site Router and Branches- 2 Location Config.
WAN for the attached topology is up and running on Channelized-E1 with IP Scheme as mentioned in the configuration file.
Need to implement PRI with any site to any site dialup option (Multiple level of backup from branch site to datacentre (Primary site and DR site).
IP Scheme for PRI is 11.1.1.0/24 and 25.1.1.0/24 on primary site router.
IP Scheme for PRI on DR site router is 12.1.1.0/24 and 21.1.1.0/24.
Need assistance in freezing the config as per the the proposed Topology.
OSPF is used with three areas defined
Area 0 - Backbone area for Datacentre router ethernet segment
Area 1 - For branches connecting to Primary datacentre site
Area 2 - For branches connecting to DR site router
Branch router is connected over lease line to primary datacentre channelized-E1, In case there is a Lease line failure at branch end or Channelized-E1 link failure at Central site , Branch router should dial in to PRI of Primary Datacentre site .
When primary datacentre site E1 as well as PRI link fails branch should dial the DR site PRI over ISDN.
Similarly branches having primary connectivity to DR site over lease line will dial the DR site PRI in case lease line fails and after PRI fails DR site branch should dial the Primary datacentre PRI over ISDN (Multiple backup scenario)
Just to summarize the requirement related to Dialup option...
Data flow for Central site branches should be in the listed order.
Data transfer from Branch (Lease Line) to Primary site (Channelized-E1) will be primary path for network operation/trafficlized-E1)
When the lease line at either branch or central site.
In case either branch lease link fails or primary site channelized-e1 link fails, branch router should automatically dial over isdn to Primary site PRI link.
In case of PRI link failure of Primary site, branch will dial to DR site PRI link as a seconday backup.
Also fourth condition ... very important.
When branch lease link and primary site channelized-e1 link comes up ISDN call initiated/connected from branch to either primary/DR site should be dropped and all the further data should take Lease line as the preferred path. As good as Fallback.Idea behind fallback is to minimize the ISDN call charges when the Lease line comec back up.
Same call flow is required for DR site branches.
Need your inputs whether the above scenario will be acheived with the OSPF cost parameter defined in the already freezed config.
Pls confirm.
Regards
DB |
|
aryoba
Premium,MVM
join:2002-08-22
| I have the following questions though
1. Is the OSPF setup already running good and you plan to add the ISDN as failover?
Or is the OSPF still on deployment?
2. Do all branches have at least two WAN links where one goes to Central Site and another goes to DR?
Or do all branches have only one WAN link that go to either Central Site or to DR?
3. Is there a reason why you would prefer ISDN over DSL? I believe you could potentially have larger bandwidth when using DSL instead of ISDN. This fact is actually main reason why some of our customer migrated from ISDN to DSL as their Frame Relay backup. |
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fmatrine
join:2005-08-08
400603
|  Hi,
Answers for you queries:-
OSPF is already running with channelized-e1 as primary link
we are trying to add ISDN failover with multisite dialing options.
Summary:-
We have half the branches connected to Primary site over lease line and rest of the branches connected to DR site over lease line as well.
At branches there is lease line and ISDN as backup media.
At Primary datacentre site we have Channelized-e1 and PRi as backup.
Similarly at DR site we have Channelized-E1 and PRI as backup for branches.
our requirement is that when primary branch lease line fails it will dial primary site PRI over ISDN.
If both , branch lease line as well as primary site PRI fails branch should dial DR site PRI.
Attaching the configuration of Primary site router, DR site router and one branch of DR site for your understanding.
Problem we are facing is that though branch lease line is UP isdn call is initiated from the branch router to both primary site as well DR site router adn stays connected.
We have different ospf cost for lease line (Low cost) and ISDN as higher cost already defined but still lease line is not preferred and calls are getting routed thru ISDN.
Rgds
DB |
|
aryoba
Premium,MVM
join:2002-08-22
1 edit | Sorry for the long delay ... been busy 
Looking at your network setup, I would prefer to do the followings:
OSPF Design and Failover Routing
1. Just use one area; area 0.
2. The Area 0 should only include Main and DR sites
3. Branches do not run OSPF; just static routes to either Main or DR sites
4. Branches' lease line have static route with low administrative distance (i.e. the default, which is 1).
5. Branches' ISDN have static route with higher administrative distance (i.e. 5)
6. Set the branches' lease line router interface to have backup interface of the ISDN.
7. By setting up the ISDN interface as backup, the ISDN would be in standby mode and only active when the lease line is down
8. Similarly, there would be static routes on Main and DR sites pointing to branches
9. The static routes would be distributed into the Area 0
10. Static routes to branches over lease line would have low administrative distance
11. Static routes to branches over ISDN would have higher administrative distance
12. Set the Main and DR lease line router interfaces to have backup interface of the ISDN |
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