OSPF : Outbound filtering

Cisco, Telecom

If you read/see videos about OSPF, it will be said that you can only filter on INBOUND or 1/0 on OUTBOUND (via ip ospf database-filter all out / neighbor x.x.x.x database-filter all out). You will say to me, no problem I can filter by means of “area range xxxxx not-advertise” (LSA Type 3) or “summary-address xxxx no-advertise” (LSA Type 5). Ok, now let’s say, I want with distribute-list and ACL, you filter out some routes ?

You could do this as :

R1(config-router)#distribute-list 10 out connected
R1(config-router)#do sh run | sec router
router ospf 1
 router-id 1.1.1.1
 no capability transit
 area 14 nssa
 summary-address 10.1.4.4 255.255.255.255 not-advertise
 summary-address 10.22.4.4 255.255.255.255 not-advertise
 network 10.1.1.1 0.0.0.0 area 0
 network 10.1.14.0 0.0.0.255 area 14
 network 11.1.1.0 0.0.0.255 area 0
 neighbor 11.1.1.2 database-filter all out
 distribute-list 10 out connected
 distance 255 9.9.9.9 0.0.0.0 41
R1(config-router)#

And you could do more :

R1(config-router)#distribute-list 10 out ?
  Async              Async interface
  Auto-Template      Auto-Template interface
  BVI                Bridge-Group Virtual Interface
  CDMA-Ix            CDMA Ix interface
  CTunnel            CTunnel interface
  Dialer             Dialer interface
  Ethernet           IEEE 802.3
  GMPLS              MPLS interface
  LongReachEthernet  Long-Reach Ethernet interface
  Loopback           Loopback interface
  Lspvif             LSP virtual interface
  MFR                Multilink Frame Relay bundle interface
  Multilink          Multilink-group interface
  Null               Null interface
  Tunnel             Tunnel interface
  Vif                PGM Multicast Host interface
  Virtual-PPP        Virtual PPP interface
  Virtual-Template   Virtual Template interface
  Virtual-TokenRing  Virtual TokenRing
  bgp                Border Gateway Protocol (BGP)
  connected          Connected
  eigrp              Enhanced Interior Gateway Routing Protocol (EIGRP)
  isis               ISO IS-IS
  lisp               Locator ID Separation Protocol (LISP)
  ospf               Open Shortest Path First (OSPF)
  ospfv3             OSPFv3
  rip                Routing Information Protocol (RIP)
  static             Static routes
  vmi                Virtual Multipoint Interface

Have lot of fun to lab all these great OSPF features.