3Com CoreBuilder 3500, Руководство по внедрению, Страница: 402 / 592

402 C
HAPTER
14: O
PEN
S
HORTEST
P
ATH
F
IRST
(OSPF)
In Figure 71, area 0.0.0.1 cannot be physically connected to the
backbone area. Instead, connectivity to the backbone is achieved using a
virtual link, configured between router A and router B. Area 0.0.0.2 is the
transit area, and router B is the entry point into backbone area 0.0.0.0.
The virtual link in Figure 71 provides area 0.0.0.1 and router A with a
logical connection to the backbone. Here is the virtual link configuration
for both routers shown in Figure 71:
■
Router A:
■
Transit area: 0.0.0.2
■
Target router: 3.1.1.1
■
Router B:
■
Transit area: 0.0.0.2
■
Target router: 2.1.1.1
Important
Considerations
Consider the following guidelines when you configure virtual links:
■
You must configure a virtual link for any area border router that has an
interface connected to a location outside the backbone area.
■
You can define up to 32 virtual links per router.
■
You cannot configure a virtual link through a stub area.
■
Use virtual links sparingly for the following reasons:
■
Stability of the virtual link depends on the stability of the
underlying area that it spans.
■
This dependency on underlying areas can make troubleshooting
difficult.