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Redundancy for two differents communication path for the same network

Posted on 2014-02-11
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Last Modified: 2014-02-18
Hi,

I have a setup like this (see the attached text file)

I have a Cisco 2901 router facing another Cisco 2901. They are using BGP for dynamic routing with private AS numbers.  So now the network is as this diagram:

We want some kind of redundancy so it will look more like the second diagram

The general idea is that in case of failure of router1(either provider or customer) communication will fall on router2 pair

For now there is only one NIC in the local server#1



So to achieve the redundancy, I was looking at different scenarios


Scenario #1: Using a virtual IP on the Cisco2901(customer) pair with HSRP so the route for the 192.168.255.0 network will not change in case of Router1 failure.  In that case that would work if the interface that I track (Wan interface) goes down.  But what if the problem is elsewhere in the cloud.  The HSRP will not see the problem and still all traffic will go to router#1.  Unless there's another way of implemeting this...



Scenario #2: Using statics route with different metric on the local server#1 (still only the local switch as single point of failure)


If there's any better idea, just explain

Thanks,
network-redundancy.txt
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Question by:fox54
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6 Comments
 
LVL 7

Expert Comment

by:unfragmented
ID: 39852677
HSRP will do your first hop routing redundancy.

Running a routing protocol like OSPF or BGP between your providers routers and your routers will sort out path selection/redundancy.
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Author Comment

by:fox54
ID: 39853185
We are running BGP on the routers.  The Local server#1 has the IP of the first customer Cisco2901 router as it's default Gateway.  So we want the Local server#1 to use the second router/path in case of the first path failure.  So what can be used to make the Local Server#1 use the second path ?  The 2901 routers are using BGP, the route in the Cisco2901 #1 will cease to have the route in it's routing table in case of a path failure but the second Cisco2901 will have it.  How can we "pass" this information on the LocalServer#1.  The Local server#1 does not use BGP and has a single NIC.
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LVL 7

Expert Comment

by:unfragmented
ID: 39853340
OK, so your scenario is R1 and R2 both up, but WAN link down on R1.

So assuming you are running HSRP and R1 is normally active, a traceroute in normal circumstances would go S1 > R1 > PE1 .....

Scenario is that R1 is up but has lost its WAN.  S1 will forward to R1.  R1 will drop traffic as it has no route out.

What you can do here is run a routing protocol between R1 and R2.  Pretty sure iBGP would work fine in this scenario but I'm a bit rusty on my BGP.  Or you can use an IGP (suggest ospf or eigrp) and redistribute BGP into your IGP.  With this, R1 will learn that it can reach your other networks via R2.

So if you were to do a traceroute during this failure scenario it would go S1 > R1 > R2 > PE2....

Make sense?
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Author Comment

by:fox54
ID: 39853366
Ok for your idea but what about this case with your scenario: R1 down

so S1 > R1(dead)....... How would S1 change to use R2 ??
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Accepted Solution

by:
unfragmented earned 500 total points
ID: 39853614
Thats a first hop routing issue.  You use HSRP to solve that, which effectively makes the default gateway IP "float" between R1and R2.

You can use HSRP in combination with BGP to give you resiliency to router failure and WAN link failure.

So a traceroute of R1 failure would look like S1 > R2 > PE2 ....
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Author Comment

by:fox54
ID: 39853620
Seems a good idea.  How do you implement that ?
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