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#Summary route calculator ipv4 full#

metric-type: keyword defines whether the LSA is listed as external type 1 or type 2 (default).

Always: default route is advertised even if there is no default route in the router’s routing table.

With this command, it injects a default route into OSPF, as an External Type 2 route, using a Type 5 LSA, with metric 1, but only if a default route exists in that router’s routing table.

ip prefix-list list-name ĭefault-information originate

On ABR02, filter subnet 2 and 3 from being advertised.Īs a result, Subnet 1 can be advertised both by ABR01 and ABR02, so we have a redundant route in case one route failed subnet 2 can only be advertised by ABR01 subnet 3 will never be advertised into Area1, therefore, subnet isolation is achieved.įirst, create a prefix list for the subnet you don’t want to advertise.

On ABR01, filter subnet 3 from being advertised.

In this case, we want to do the following configuration: Type 3 LSA filtering tells the ABR to filter the advertisement of these Type 3 LSAs, this essentially stops the type 3 LSAs represent all subnets in other areas from been flooded into the area been specified. ABR creates and flood type 3 summary LSAs into one area to represent the subnets in the other areas connected to that ABR.

Filtering the router that OSPF would normally add to the IP routing table on a single router.ĪBR connect to the backbone area and at least one other area.

Therefore, Cisco IOS limits OSPF route filtering to the following: Because of the underlying distance vector logic, an OSPF ABR can be configured to filter Type 3 LSAs, with no risk of creating routing loops. OSPF does allow some route filtering, however, taking advantage of the fact that OSPF uses distance vector logic with Type 3 LSAs ( and Type 5 used for external routes).

This means that no additional SPF calculation is required to find all interarea routes for a given prefix/length, making the logic more like distance vector logic. To choose the best interarea route, a router use distance vector logic of taking its known metric to reach the ABR and adds the metric for that subnet as advertised by the ABR. The intra-area SPF calculation includes the calculation of the metric of the best route to reach each ABR in the area. interarea routesįor interarea routes, OSPF use distance vector logic.

As a result, OPFS can not and does not allow the filtering of LSAs inside an area. However, inside one area, all routers must know all LSAs, so the entire SPF concept will fail, and routing loops could occur. Any filtering applied to OSPF messages would need to filter the transmission of LSAs. If we use Route filtering inside one area, first, OSPF routers do not advertise routes instead, they advertise LSAs.

This logic relies on all routers inside the area having an identical copy of the link-state database (LSDB) for that area.

#Summary route calculator ipv4 full#

OSPF use pure link-state logic for intra-area routes, with full topology information about an area, piecing together the topology map from the Type 1 and Type 2 LSAs.

peer 3.3.3.First, we need to know the difference in how OSPF choose intra-area versus interarea routes. This value is greater than the preferred value (0) for IPv4 unicast routes from CE 2, so PE 1 prefers the routes from PE 2. # Specify the preferred value as 200 for BGP VPNv4 routes received from PE 2. # Configure FRR for VPN instance vpn1 to use routing policy frr. apply fast-reroute backup-nexthop 10.1.1.1 ip prefix-list abc index 10 permit 4.4.4.4 32 # Create routing policy frr, and specify the backup next hop as 10.1.1.1 for the route to 4.4.4.4/32. # Configure BFD to test the connectivity of the LSP to 2.2.2.2/32. (Details not shown.)įor more information about configuring basic MPLS 元VPN, see " Example: Configuring basic MPLS 元VPN." To have an interface operate, you must use the undo shutdown command to enable that interface.Ĭonfigure IP addresses and masks for interfaces as shown in Table 24, and configure BGP and MPLS 元VPN. By default, interfaces on the device are disabled (in ADM or Administratively Down state).