Configuring Virtual Links - Dell PowerConnect B-RX Configuration Manual

Configuring virtual links

All ABRs must have either a direct or indirect link to an OSPF backbone area (0.0.0.0 or 0). If an
ABR does not have a physical link to a backbone area, you can configure a virtual link from the ABR
to another router within the same area that has a physical connection to the backbone area.
The path for a virtual link is through an area shared by the neighbor ABR (router with a physical
backbone connection) and the ABR requiring a logical connection to the backbone.
Two parameters must be defined for all virtual links—transit area ID and neighbor router.
•
•
NOTE
By default, the Brocade router ID is the IPv4 address configured on the lowest numbered loopback
interface. If the Brocade device does not have a loopback interface, the default router ID is the
lowest numbered IPv4 address configured on the device.
NOTE
When you establish an area virtual link, you must configure it on both of the routers (both ends of
the virtual link).
For example, imagine that ABR1 in areas 1 and 2 is cut off from the backbone area (area 0). To
provide backbone access to ABR1, you can add a virtual link between ABR1 and ABR2 in area 1
using area 1 as a transit area. To configure the virtual link, you define the link on the router that is
at each end of the link. No configuration for the virtual link is required on the routers in the transit
area.
To define the virtual link on ABR1, enter the following command on ABR1.
BigIron RX(config-ospf6-router)# area 1 virtual-link 209.157.22.1
To define the virtual link on ABR2, enter the following command on ABR2.
BigIron RX(config-ospf6-router)# area 1 virtual-link 10.0.0.1
Syntax: area <number> | <ipv4-address> virtual-link <router-id>
The area <number> | <ipv4-address> parameter specifies the transit area.
The <router-id> parameter specifies the router ID of the OSPF router at the remote end of the
virtual link. To display the router ID on a router, enter the show ip command.
Assigning a virtual link source address
When routers at both ends of a virtual link need to communicate with one another, the source
address included in the packets must be a global IPv6 address. Therefore, you must determine the
global IPv6 address to be used by the routers for communication across the virtual link. You can
specify that a router uses the IPv6 global address assigned to one of its interfaces.
For example, to specify the global IPv6 address assigned to Ethernet interface 3/1 on ABR1 as the
source address for the virtual link on ABR1, enter the following command on ABR1.
BigIron RX Series Configuration Guide
53-1001986-01
The transit area ID represents the shared area of the two ABRs and serves as the connection
point between the two routers. This number should match the area ID value.
When assigned from the router interface requiring a logical connection, the neighbor router
field is the router ID (IPv4 address) of the router that is physically connected to the backbone.
When assigned from the router interface with the physical connection, the neighbor router is
the router ID (IPv4) address of the router requiring a logical connection to the backbone.
Configuring OSPFv3
48
1193