Routing Querry

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Jul 14th, 2009
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Hello Netpros,

Kindly suggest me the possible way for achieving as desired.

We have two Cisco Switches (Switch “1” & Switch “2”) which is connected to remote end i.e provider's network running with BGP protocol. Diagram attached.


As of now one non-cisco RAS devices connected with Switch-1 at one end and another end of Non-Cisco RAS with “Access Switch”. Traffic from acces devices are follow this path:-

Access Devices --> Access Switch --> Non Cisco RAS device --> Switch-1 --> Remote end (Providers Network).


We'll connected Non-Cisco RAS with one more switch i.e Switch-2 which is connected to Providers network running with BGP protocol as like Switch-1.

In case of failure of Switch-1 both WAN Links or WAN ports the traffic from Non-Cisco (RAS) will automaticallty swithover on another switch(Switch-2). i.e In case of Switch-1 WAN Link/Ports failure , path will be as:-

Access Devices --> Access Switch --> Non Cisco RAS device --> Switch-2 --> Remote end (Providers Network).

Points To Remember :-

1)Use of Routing protocols are not recommended on Non-Cisco device(RAS). We can only use static route on the same with Higher Metric towards Switch-2. As Primary route is towards Switch.-1

2) Link between Switch-1 or Switch-2 & NoN Cisco RASD device will always be UP as it is directly connected.


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Overall Rating: 5 (1 ratings)
Giuseppe Larosa Tue, 07/14/2009 - 08:38
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Hello Jimmy,

look for reliable static routing it is the only way to handle a scenatio like this without dynamic routing


But if your switches don't support it, and this is possible, you are in troubles.

You should think of BGP but again I'm not sure that all your devices will support it.

Hope to help

Giuseppe Wed, 07/15/2009 - 07:25
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Hii Giuseppe,

All devices will support all routing protocols except one i.e Non-Cisco RAS(Even it is also supporting , but not recommended by manufacturer hence working on Static route only)

In my scerio there is one more point.

As mentioned Switch-1 & Switch-2 is running with BGP with remote end (Providers network). And primarily Non-Cisco device traffic/access switch traffic( Access traffic IP pools is advertised on BGP at Switch-1 and then at providers end respective device).....but in case if Switch-1 WAN link failure and if we get success in auto-switching of traffic towards Switch-2 we also need to advertise same IP pools on BGP at Switch-2 and at respective device at providers this possible to advertise same pools on two pairs of devices running with BGP or any other routing protocols...?

Giuseppe Larosa Wed, 07/15/2009 - 07:36
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Hello Jimmy,

>> .is this possible to advertise same pools on two pairs of devices running with BGP or any other routing protocols...?

This is possible but the key point here is fault detection and reaction to it.

You need also to take care of faults inside the network.

Hope to help

Giuseppe Thu, 07/16/2009 - 08:29
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Hi Giuseppe,

:)) , Lets go ahead with discussion for acheiving the scenrio. have to take the risk for something good.

Can u pls help me to desgn possible way..pls.

Giuseppe Larosa Thu, 07/16/2009 - 11:38
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Hello Jimmy,

as I explained in my first post if you cannot use dynamic routing protocols you need to use object tracking as in that link I've provided.

The idea is that you configure static routes towards the RAS device for the internal networks (one for each subnet)

Then you define a test like a ping to a specific address in the subnet to verify that it is alive.

Until it is alive the static route is present in the routing table:

it can be used for forwarding of packets

it can be used by a BGP network command to advertise the IP subnet.

This on edge BGP routers

In the same way, internal routers after the RAS device can have default static routes towards BGP routers via the RAS device, and they can check the good health of BGP device1 and of its eBGP connection (for example pinging an ISP1 ip address)

So that they can switch to secondary route in case of failure.

BGP router2 if needed can use BGP conditional advertising to advertise prefixes only when BGP router1 stops to advertise them.

So a direct connection between the two BGP routers to run an iBGP session is useful.

All this put together can work.

The details of configuration are IOS version dependent.

The first preliminary step is to understand if your devices support object tracking.

If you like you can post a list of devices and IOS version for the BGP routers and the internal devices.

if this solution cannot be used we can think of using BGP sessions to provide state information.

Hope to help

Giuseppe Sun, 07/19/2009 - 01:55
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HI Giuseppe,

Sure . Will provide you the IOS details shortly for further suggestions.

Joseph W. Doherty Sun, 07/19/2009 - 03:43
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Is it possible to drop any other devices between RAS and switches 1 and 2?

Is it possible to define shared VLAN between switches 1 and 2 and RAS device? (I.e. all 3 would logically be on same LAN segment.)

If you can do either of the above, likely opens new options for what you might be able to do.


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