Product guide

IP Routing Features
Configuring OSPF
Configuring OSPF Authentication on a Virtual Link
OSPF supports the same two methods of authentication for virtual links as it
does for VLANs and subnets in an area—password and MD5. In the default
configuration, OSPF authentication is disabled. Only one method of authen-
tication can be active on a virtual link at a time, and if one method is configured
on a virtual link, then configuring the alternative method on the same link
automatically replaces the first method with the second. Both ends of a virtual
link must use the same authentication method (none, password, or MD5 key
chain) and related credentials. (Any interfaces that share a VLAN or subnet
with the interface used on an ABR for a virtual link, including intermediate
routing switches, must be configured with the same OSPF authentication.)
OSPF Password Authentication on a Virtual Link.
Syntax: area < area-id > virtual-link < ip-addr > authentication-key < octet-string >
no area 1 virtual-link < ip-address > authentication
Used to configure password authentication in the router OSPF
context on both ABRs in a virtual link . The password takes
effect immediately, and all OSPF packets transmitted on the
link contain this password. Every OSPF packet received on the
interface for the virtual link on each ABR is checked for the
password. If it is not present, then the packet is dropped. To
disable password authentication on an ABR interface used for
a virtual link, use the no form of the command. The password
must be the same on both ABRs on a given virtual link.
< area-id >: Specifies the OSPF area in which both ABRs in a
given virtual link operate. In this use, the area ID is sometimes
termed “transit area ID”. This value must be the same for both
ABRs in the virtual link.
< ip-addr >: For an ABR in a given virtual link, this is the IP
address used to create the link on that ABR. (This IP address
matches the IP address of the interface on the opposite end of
the virtual link. Refer to the description of < ip-address > in the
syntax description under “Configuring a Virtual Link” on
page 5-83.)
< octet-string >: An alphanumeric string of one to eight
characters. (Spaces are not allowed.) To change the password,
re-execute the command with the new password.
Note: To replace the password method with the MD5 method
on a given interface, overwrite the password configuration by
using the MD5 form of the command shown in the next syntax
description. (It is not necessary to disable the currently
configured OSPF password.)
Default: Disabled
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