#format wiki
#language en
= OSPF routing links and notes =
 * This is not a explanation of ospf, just interesting notes.

 * sham-links -> ospf + mpls-mp-bgp
   * The problem 
     * When using a providers mpls network to connect site, ospf is redistributed into bgp and back out to ospf at the other sites.
     * The problem is that the routes are redistributed back to ospf as inter-area(From another area)
     * this causes ospf to ignore the route, if there is any other intra-area(Same area) links available.
   * Links to sham-link bgp examples [[http://blog.ine.com/2010/04/08/a-sham-link-really-yes-and-its-not-used-for-phishing/]]
   * Solution
     *  [[http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15-sy/iro-15-sy-book/iro-sham-link.html|Cisco]]
     * sham-links changes the behavior on PE routers
   * Config of sham links
     * Each PE needs loopback in same vrf as sham endpoints, e.g. 99.99.99.1, should be able to ping loopbacks in vrf from PE to PE
     * Under PE ospf add sham link
       {{{
SPEDGE1(config)#router ospf 2 vrf CUSTOMER
SPEDGE1(config-router)#area 0 sham-link 99.99.99.1 99.99.99.2
!
       }}}
     * Redistribution OSPF -> MP-BGP with sham link ?
       * We dont need any redistribution from BGP into OSPF
       * but from OSPF into BGP, because MP-BGP needs to have the prefixes in its routing table to use LDP for the VPN-label-assignment.
    
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