A Close Look at the Redistribution of OSPF Routes into BGP in the ProCurve

As an example, consider the following network diagram:

OSPF Area 0 includes switches SW1, SW3 and SW4. In SW3, a static route to network 10.8.0.0/16 is configured, and this static route is configured to be redistributed into OSPF. Also in SW3, subnet 192.168.13.0/24 (or VLAN 13) is connected and also configured to be redistributed into OSPF.

We will focus on SW1, where both OSPF and BGP are configured, and where OSPF routes are exported into BGP.

First, the routing table in SW1 will look like this:

Notice that SW1 learned 3 routes from OSPF:

- 10.12.30.0/24 (VLAN 30) generated from with OSPF, hence listed here as "IntrArea" and considered an internal route.
- 10.8.0.0/16 and 192.168.13.0/24 (VLAN 13) distributed into OSPF from "static" and "connected", hence listed here as "External2" and considered external routes.

Now let's look at the distribution of these OSPF routes into BGP in SW1. Below is how SW1 is configured under BGP router (Scenario 1):

router bgp 1200
    enable
    redistribute ospf
    neighbor 192.168.20.2 remote-as 1300
    exit

With the above configuration, the BGP routing table in SW1 will look like:

As seen in the screenshot above, only the OSPF route 10.12.30.0/24 appeared in the BGP routing table. The reason is that the command "redistribute ospf" under BGP only exports OSPF internal routes into BGP. All external routes are excluded from the redistribution.

Now consider another BGP configuration in SW1 (Senario 2):

router bgp 1200
    enable
    network 10.8.0.0 255.255.0.0
    redistribute ospf
    neighbor 192.168.20.2 remote-as 1300
    exit

In this configuration, under BGP we have the command "network 10.8.0.0 255.255.0.0". The resulting BGP routing table will looks like:

In the screenshot above, in addition to the OSPF internal route of 10.12.30.0/24 (VLAN 30) which is exported into BGP by the command redistribute ospf, the route to subnet 10.8.0.0/16 also appears in the BGP table because in this scenario we have the command network 10.8.0.0 255.255.0.0 under BGP. In contrast, a route to subnet 192.168.13.0/24 (VLAN 13) is not present in the BGP routing table because this subnet is not configured with the network command under BGP.

The bottom line is that in the ProCurve, OSPF external routes cannot be exported into BGP using the redistribute command. They have to be specified using the network command under BGP to be present in the BGP routing table. This is different from Cisco IOS, which allows the export of OSPF external routes into BGP by the command redistribute ospf 1 match external.

ProCurve Switches - Configuring a Failover Link in OSPF

In the above example, switch ProCurve A has two connections to network 10.10.13.0/24. Switch ProCurve A needs to be configured in such a way that when both connections are up, the traffic to and from network 10.10.13.0/24 will pass through ProCurve B (the main link). If the main link is down then the backup link through ProCurve C will carry that traffic. All three ProCurve switches run OSPF for routing.

The method described below also works in the scenario where the main link is connected to the Internet via ISP 1 (the preferred ISP) and the backup link is connected to the Internet via ISP 2. Just replace the remote network address (10.10.13.0/24 in this example) by 0.0.0.0/0.

Using static routes with different administrative distances, then redistribute them into OSPF:

In ProCurve A, configure two static routes as follows:

HP-5406zl(config)# ip route 10.10.13.0/24 192.168.200.2 distance 10
HP-5406zl(config)# ip route 10.10.13.0/24 192.168.300.2 distance 20
HP-5406zl(config)# router ospf redistribute static

The link through ProCurve B has a lower distance than the backup link, so it will be chosen to carry traffic to and from network 10.10.13.0/24 under normal conditions. When this link fails, the link through ProCurve C will kick in as backup. The last command makes sure that these static routes be redistributed throughout the OSPF domain.

In the first two commands, the parameter metric can be modified instead of distance. The effect will be the same.