3Com 7700 Configuration Manual page 96

88 C 5: R P
HAPTER OUTING
O
ROTOCOL PERATION
Perform the following configuration in OSPF Area view.
Table 36 Configure the Route Summarization of an OSPF Area
Operation
Configure the Route
Summarization of OSPF Area
Cancel route summarization of
OSPF Area
By default, the inter-area routes are not summarized.
Configure OSPF Virtual Link
According to RFC2328, after the area division of OSPF, The backbone are is
established with an area-id of 0.0.0.0. The OSPF routes between non-backbone
areas are updated with the help of the backbone area. OSPF stipulates that all the
non-backbone areas should maintain connectivity with the backbone area and at
least one interface on the ABR should fall into the area 0.0.0.0. If an area does not
have a direct physical link with the backbone area 0.0.0.0, a virtual link must be
created.
If physical connectivity cannot be made due to network topology restrictions, a
virtual link can be used to meet the requirements of RFC 2328. The virtual link
refers to a logic channel set up through the area of a non-backbone internal route
between two ABRs. The two ends of the channel should be ABRs and the
connection can take effect only when both ends are configured. The virtual link is
identified by the ID of the remote router. The area, which provides the ends of the
virtual link with a non-backbone area internal route, is called the transit area. The
ID of the transit area should be specified during configuration.
The virtual link is activated after the route passing through the transit area is
calculated, which is equivalent to a P2P connection between two ends. Therefore,
similar to the physical interfaces, you can also configure various interface
parameters on this link, such as a hello timer.
The "logic channel" means that the multiple routers running OSPF between two
ABRs only take the role of packet forwarding (the destination addresses of the
protocol packets are not these routers, so these packets are transparent to them
and the routers forward them as common IP packets). The routing information is
directly transmitted between the two ABRs. The routing information refers to the
type-3 LSAs generated by the ABRs, for which the synchronization mode of the
routers in the area is not changed.
Perform the following configuration in OSPF area view.
Table 37 Configure OSPF Virtual Link
Operation
Create and configure a virtual
link
Remove the created virtual link undo vlink-peer router-id
Command
abr-summary ip-address mask [ advertise |
not-advertise ]
undo abr-summary ip-address mask
Command
vlink-peer router-id [ hello seconds] [ retransmit seconds ] [
trans-delay seconds ] [ dead seconds] [ simple password |
md5 keyid key ]