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New Member

BGP Single Multi-homed Local Preference Issue

I have a Single Multi-homed two router design, connection to my ISP's.  One ISP is Cox Communications and the other is Centurylink.  Cox connection is 100 megs.  Centurylink is 20 megs.  All of my VPN sites work fine with this design until I tune Local Pref.  In other words, I can shutdown the Cox router and VPN sites connect over Centurylink.  If I shutdown Centurlink, then all sites will connect over Cox.  Both paths are successful.  


The problem comes in when I set the Local Pref on my Cox router as the preferred router.  Because my Cox router is 100 megs I want it to be the preferred path on outbound traffic.  In order to do this I set the BGP local preference to 200.  This works great in my lab to push traffic out of Cox.  That said, for some reason, one of my T1 Centurylink VPN sites, "Alexandria", loses connectivity completely whenever I set the Local Pref on the Cox router.  I cannot ping it at all.  I know the connection is still up because we have tested from the other end.  The interesting thing is that Alexandria can connect over the Cox connection with no problems when I bring the Centurylink connection down.  

Any ideas on what may be causing this issue?  It is so weird.


Hello are these VPN sites in



are these VPN sites in the same as domain than the primary and secondary hubs?

are you advertising the physical subnets of your  hubs to the vans sites?




Please don't forget to rate any posts that have been helpful. Thanks.
New Member

 I would start with a


I would start with a traceroute and a show ip route when you have the local pref modified and giving you headaches. Otherwise its just shooting in the dark.


New Member

Local Pref will choose your

Local Pref will choose your outbound.  What are you doing for your inbound?  Are you prepending your AS?

Have you checked if the

Have you checked if the Alexandria subnet is advesrtised to CoX?