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New Member

Routing Issues******************************

Hi Expertise,

I have a Cisco 1841 acting as my core router (with HSRP to another 1841). I have 2 more routers on which MPLS ckt is getting terminated. My branches are getting connected to my LAN via MPLS. LAN users are accessing internet via core route that is 1841. What I want to do is if my core router goes down my LAN internet traffic revert on MPLS ckt. If one MPLS ckt is also down it revert on second MPLS router. Entire LAN have ospf topology. Pls suggest ur valuable output. Is SLA based routing support on this, if yes HOW??

6 REPLIES

Re: Routing Issues******************************

Hi

can you post out a small diagram representing your current connectivity and your requirement ?

regds

New Member

Re: Routing Issues******************************

Hi,

Thanks for ur reply, pls find attached nw diagram.

Re: Routing Issues******************************

Hi

After seeing your diagram i feel you want your traffic to be routed via 2851 Series router then onto MPLS Cloud instead of the normal flow via 2821 routers when the 2821 routers fails ...

I feel in this case your core switch 4503 can be the made to take the routing decision during normal and failure sate.

without much of details on Firewall/IPS and other lan device configs policies i speculate that you can make use of a routing protocol possibly OSPF to inject a default route onto the core switch to make use of the same during normal condition and when the core router goes down then the same will be removed and the traffic can be re routed via the secondary path through the 2851 router.

regds

Re: Routing Issues******************************

Hi

After seeing your diagram i feel you want your traffic to be routed via 2851 Series router then onto MPLS Cloud instead of the normal flow via 2821 routers when the 2821 routers fails ...

I feel in this case your core switch 4503 can be the made to take the routing decision during normal and failure sate.

without much of details on Firewall/IPS and other lan device configs policies i speculate that you can make use of a routing protocol possibly OSPF to inject a default route onto the core switch to make use of the same during normal condition and when the core router goes down then the same will be removed and the traffic can be re routed via the secondary path through the 2851 router.

regds

New Member

Re: Routing Issues******************************

Hi,

My entire device lies in area0. As i know if we define only one area in that case no default route comes in picture.

Is SLA based routing help me out ??

Hall of Fame Super Silver

Re: Routing Issues******************************

Hello Ashish,

even in a OSPF single-area an OSPF default route can be injected as an O E2 (by default ) using LSA type 5.

the router that has to send the default-route need to:

a) have a default route installed in its routing table by any method including a default static route

b) inside router ospf

default-information originate

this command accepts a reference to a route-map that can be used to modify the default route attributes (metric and metric type) and to check if some conditions are true (to check the ip next-hop for the installed default-route for example)

the command accepts also the option always but in this case the OSPF 0.0.0.0/0 LSA is sent always even if no default route exists in the local routing table.

So as you can see OSPF offers enough flexibility for default route injection in the OSPF domain and you don't need a multi-area scenario.

Hope to help

Giuseppe

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