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Dual Internet Connections with OSPF and Dual GLR's

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Dec 28th, 2011
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It has been a long time (a very very long time) since I have been a technician so I need some help from folks who are current.  We recently lost our senior Engineer.  We have two Internets links at two geographically separate locations connected to our WAN and are currently using only OSPF, static routing, and one gateway of last resort to direct traffic. We want to configure our network to have some WAN sites go through Internet connection 1 and some go through internet connection 2 for load balancing and fault tolerance.  When one link goes down we want all traffic to get to the Internet via the remaining link and when the link comes back up go back to load balancing and renew fault tolerance. We currently have one GLR with the GLR set using information originate. How can we configure dual GLR’s to achieve the above scenario?  One problem is that our external firewall (5545) is not doing any routing so when an Internet link goes down, we are not sure how to get the link status injected into OSPF.  The external firewall is separated from internal traffic by a DMZ and internal 5545 firewall. I have been browsing around and saw something called ****  track 123 ip sla 1 reachability ****.  This command did not even exist when I was doing routing.  Is there a cookbook for this that I can get from Cisco or an example?  We want to stay with OSPF if possible. Thanks for reading this long message.  Help would be appreciated.

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cadet alain Wed, 12/28/2011 - 07:33
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Hi,


can you provide a diagram with  the devices involved, their status( routing, transparent, L2 or L3) as well as where the Routing protocol is enabled and if you're using static default for WAN.


The sla feature  along with tracking is used for failover but we need  more infos to give you a correct link to help.


Regards.


Alain

chalonec.roger@... Wed, 12/28/2011 - 08:15
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Thanks for the reply.  I have attached a redacted diagram.  Each sitre looks like the attched diagram




UPDATE:  Alain,  the digram does not show how the internal connections are made.  They are made with 6500 switches running OSPF and propagating the GLR.  Everyting else on the  DMZ uses static routes.


Thanks..

cadet alain Wed, 12/28/2011 - 11:15
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Hi,

so between the 2 DMZ this is a L3 switch ?

Can you detail more about the VRRP part and explain where are static routes and OSPF configured.


Regards.


Alain

chalonec.roger@... Thu, 12/29/2011 - 03:34
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The switch on the DMZ is layer 2.  Hosts on the DMZ have static routes to get to internal hosts.  Not too sure the VRRP part but the upstream device is our ISP. OSPF resides on a 6500 on the internal network which can be reached by DMZ hosts with their staic routes.  No OSPF on DMZ.

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