area virtual-link
Use this command to configure a link between two backbone areas that are physically separated through other non-backbone area.
In OSPF, all non-backbone areas must be connected to a backbone area. If the connection to the backbone is lost, the virtual link repairs the connection. Configure virtual links between any two backbone routers that have an interface to a common non-backbone area. The protocol treats these routers joined by a virtual link as if they were connected by an unnumbered point-to-point network.
Configure the hello-interval to be the same for all routers attached to a common network. A short hello-interval results in the router detecting topological changes faster but also an increase in the routing traffic. The retransmit-interval is the expected round-trip delay between any two routers in a network. Set the value to be greater than the expected round-trip delay to avoid needless retransmissions.
The transmit-delay is the time taken to transmit a link state update packet on the interface. Before transmission, the link state advertisements in the update packet, are incremented by this amount. Set the transmit-delay to be greater than zero. Also, take into account the transmission and propagation delays for the interface. Include the transit area ID and the corresponding virtual link neighbor’s router ID in each virtual link neighbor to properly configure a virtual link.
Use the no parameter with this command to remove a virtual link.
Command Syntax
area (A.B.C.D|<0-4294967295>) virtual-link A.B.C.D
area (A.B.C.D|<0-4294967295>) virtual-link A.B.C.D {authentication (message-digest|null|)|authentication-key LINE|message-digest-key <1-255> md5 LINE}
area (A.B.C.D|<0-4294967295>) virtual-link A.B.C.D {dead-interval <1-65535>|hello-interval <1-65535>|retransmit-interval <1-3600>|transmit-delay <1-3600>}
area (A.B.C.D|<0-4294967295>) virtual-link A.B.C.D fall-over bfd
no area (A.B.C.D|<0-4294967295>) virtual-link A.B.C.D
no area (A.B.C.D|<0-4294967295>) virtual-link A.B.C.D {authentication (messagedigest| null|)|authentication-key LINE|message-digest-key <1-255> md5 LINE}
no area (A.B.C.D|<0-4294967295>) virtual-link A.B.C.D {dead-interval <1-65535>|hello-interval <1-65535>|retransmit-interval <1-3600>|transmit-delay <1-3600>}
no area (A.B.C.D|<0-4294967295>) virtual-link A.B.C.D fall-over bfd
Parameters
A.B.C.D
OSPF Area ID in IPv4 address format.
<0-4294967295>
OSPF Area ID as a decimal value.
A.B.C.D
Specify IP address of the virtual link neighbor.
authentication
Enable authentication on this virtual link
message-digest
Cryptographic authentication.
null
Null authentication.
authentication-key
Set authentication key.
LINE
Authentication key ID of 8 characters.
message-digest-key
Set message digest key.
<1-255>
Set message digest key.
md5
Specify the MD5 key.
LINE
MD5 key.
dead-interval
The interval during which no packets are received and after which the router acknowledges a neighboring router as off-line.
<1-65535>
The interval in seconds. The default is 40 seconds.
hello-interval
The interval the router waits before it sends a hello packet.
<1-65535>
The interval in seconds. The default is 10 seconds.
retransmit-interval
The interval the router waits before it retransmits a packet.
<1-3600>
The interval in seconds. The default is 5 seconds.
transmit-delay
The interval the router waits before it transmits a packet.
<1-3600>
The interval in seconds. The default is 1 second
fall-over
Specify fall-over detection.
bfd
Bidirectional Forwarding Detection (BFD)
Default
Default intervals:
Dead interval : 40 seconds
Hello interval: 10 seconds
Retransmit interval: 5 seconds
Transmit delay: 1 second
Command Mode
Router mode
Applicability
This command was introduced before OcNOS version 1.3
Examples
#configure terminal
(config)#router ospf 100
(config-router)#area 1 virtual-link 10.10.11.50 hello 5 dead 10
The below example shows the differences between with and without encrypted passwords.
0x - Already encrypted password
WORD - Authentication key (without encryption, ie doesn’t begin with 0x)
(config-router)#area 0.0.0.1 virtual-link 2.2.2.2 authentication authentication-key 0x1234567891234567
(config-router)#area 0.0.0.1 virtual-link 2.2.2.2 authentication authentication-key test
Last modified date: 10/16/2023