PE-to-CE Connectivity?OSPF Without Site Area 0 Support

The second OSPF connectivity option is to place the PE-to-CE link into a non-backbone area. In this case, the PE-router acts as an ABR (and an ASBR) for the customer site, and forms an adjacency with the CE-router so that it can exchange LSAs. An illustration of this connectivity option can be seen in Figure 10-7.

Figure 10-7. PE-to-CE Connectivity?Without Site Area 0 Support


Figure 10-7 shows that the FastFoods San Jose CE-router has an adjacency with the SuperCom San Jose PE-router in OSPF area 1. The Type-1 LSA describing the prefix is received by the SuperCom San Jose PE-router and is placed into the FastFoods VRF. This LSA can be seen in Example 10-12.

Example 10-12 Router LSA for FastFoods San Jose CE-router

San Jose# show ip ospf data router

       OSPF Router with ID ( (Process ID 100)

                Router Link States (Area 1)

  LS age: 1707

  Options: (No TOS-capability, DC)

  LS Type: Router Links

  Link State ID:

  Advertising Router:

  LS Seq Number: 80000002

  Checksum: 0xE118

  Length: 48

   Number of Links: 2

    Link connected to: a Stub Network

     (Link ID) Network/subnet number:

     (Link Data) Network Mask:

      Number of TOS metrics: 0

        TOS 0 Metrics: 1

    Link connected to: a Transit Network

     (Link ID) Designated Router address:

     (Link Data) Router Interface address:

      Number of TOS metrics: 0

       TOS 0 Metrics: 1

This route is then redistributed into MP-iBGP and is advertised across the MPLS/VPN backbone as an intra-area route. This is highlighted by the OSPF route type of 1:2:0 shown in Example 10-13, where the 1 signifies that the route belongs to OSPF area 1, and the 2 signifies that the route type is intra-area.

Example 10-13 Population of VRF with OSPF Routes for Non-area 0 Support

San Jose# show ip route vrf FastFoods

Routing entry for

  Known via "ospf 100", distance 110, metric 2, type intra area

  Redistributing via bgp 1, ospf 100

  Advertised by bgp 1 match internal external 1 & 2

  Last update from on FastEthernet0/0, 00:30:59 ago

  Routing Descriptor Blocks:

  *, from, 00:30:59 ago, via FastEthernet0/0

      Route metric is 2, traffic share count is 1

San Jose# show ip bgp vpnv4 vrf FastFoods

BGP routing table entry for 1:26:, version 102

Paths: (1 available, best #1, table FastFoods)

  Advertised to non peer-group peers:

  Local from (

      Origin incomplete, metric 2, localpref 100, weight 32768, valid,

      sourced, best

      Extended Community: RT:100:26 OSPF RT:1:2:0

When the route is received by the SuperCom Paris PE-router and is imported into the FastFoods VRF, a summary LSA for the route is advertised into the FastFoods site in Lyon. This summary LSA can be seen in Example 10-14.

Example 10-14 Summary-LSA Across PE to CE Link?Non-area 0 Support

Paris# show ip ospf data summary

       OSPF Router with ID ( (Process ID 100)

                Summary Net Link States (Area 1)

  LS age: 1533

  Options: (No TOS-capability, DC, Downward)

  LS Type: Summary Links(Network)

  Link State ID: (summary Network Number)

  Advertising Router:

  LS Seq Number: 80000001

  Checksum: 0xED1F

  Length: 28

  Network Mask: /32

        TOS: 0  Metric: 2 

    Part 2: MPLS-based Virtual Private Networks