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Chapter 20 IPSec VPN
ZyWALL 110/310/1100 Series User’s Guide
301
20.4 VPN Concentrator
A VPN concentrator combines several IPSec VPN connections into one secure network.
Figure 183 VPN Topologies (Fully Meshed and Hub and Spoke)
In a fully-meshed VPN topology (1 in the figure), there is a VPN connection between every pair of
routers. In a hub-and-spoke VPN topology (2 in the figure), there is a VPN connection between
each spoke router (B, C, D, and E) and the hub router (A), which uses the VPN concentrator. The
VPN concentrator routes VPN traffic between the spoke routers and itself.
A VPN concentrator reduces the number of VPN connections that you have to set up and maintain in
the network. You might also be able to consolidate the policy routes in each spoke router,
depending on the IP addresses and subnets of each spoke.
However a VPN concentrator is not for every situation. The hub router is a single failure point, so a
VPN concentrator is not as appropriate if the connection between spoke routers cannot be down
occasionally (maintenance, for example). There is also more burden on the hub router. It receives
VPN traffic from one spoke, decrypts it, inspects it to find out to which spoke to route it, encrypts it,
and sends it to the appropriate spoke. Therefore, a VPN concentrator is more suitable when there is
a minimum amount of traffic between spoke routers.
Client Mode Select this radio button if the ZyWALL provides a username and password to the remote
IPSec router for authentication. You also have to provide the User Name and the
Password.
User Name This field is required if the ZyWALL is in Client Mode for extended authentication. Type
the user name the ZyWALL sends to the remote IPSec router. The user name can be 1-
31 ASCII characters. It is case-sensitive, but spaces are not allowed.
Password This field is required if the ZyWALL is in Client Mode for extended authentication. Type
the password the ZyWALL sends to the remote IPSec router. The password can be 1-31
ASCII characters. It is case-sensitive, but spaces are not allowed.
OK Click OK to save your settings and exit this screen.
Cancel Click Cancel to exit this screen without saving.
Table 110 Configuration > VPN > IPSec VPN > VPN Gateway > Edit (continued)
LABEL DESCRIPTION
12