User guide

12-8 E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
I
NTERIOR
G
ATEWAY
R
OUTING
P
ROTOCOLS
perform translation (as indicated in the NSSA specification). The option should not be
used on NSSA internal routers. Doing so inhibits correct operation of the election
algorithm.
N
ORMAL
A
REA
A normal area is an area that is not any of the following:
• Area 0
• Stub area
• NSSA
Virtual links can be configured through normal areas. External routes can be distributed
into normal areas.
V
IRTUAL
L
INKS
In the situation when a new area is introduced that does not have a direct physical
attachment to the backbone, a virtual link is used. A virtual link provides a logical path
between the ABR of the disconnected area and the ABR of the normal area that
connects to the backbone. A virtual link must be established between two ABRs that
have a common area, with one ABR connected to the backbone. Figure 12-1 illustrates a
virtual link.