JUNOS High Availability

Routing Protocol Interoperability

Figure 15-5 illustrates a few issues you may encounter when running common industry-standard routing protocols among Juniper and Cisco routers. In this figure, devices from different vendors have been mixed in a rather haphazard way to trigger certain issues that we want to address. The figure does not necessarily reflect a layered or site-based approach to multivendor networks.

Figure 15-5. Base topology for IGP and BGP interoperability concerns

In Figure 15-5, routers r2, r3, and r5 share OSPF adjacencies, which use MD5 authentication, and Internal BGP (IBGP) relationships within AS 64512. Router r5 is an External BGP (EBGP) peer to r1 in AS 100. Routers r2 and r3 are EBGP peers to r4 in AS 400.

In this example, we assume that AS 64512 contains other Cisco devices that are connected in a partial mesh. Router r5 represents the collection of Cisco routers.

Interface Connectivity

Before bringing up OSPF or BGP relationships among the Cisco and Juniper devices, we must first establish simple Layer 3 connectivity. Assuming that all physical cabling is in place, we add the necessary configuration elements for the Cisco–Juniper connections on r5. This snippet shows Fast Ethernet interfaces 0/0 and 0/1 configured with appropriate IP addresses for connectivity to r3 and r2. We also see the appropriate address for serial interface 0/0 and confirm that a loopback ...