NetModule NB3711, Руководство пользователя, Страница: 75 / 214

NB3711 User Manual 4.0
5.4.4. Mobile IP
Mobile IP (MIP) can be used to enable seamless switching between different kinds of
WAN links (e.g. WWAN/WLAN). The
mobile node
hereby remains reachable via the
same IP address (
home address
) at any time, independently of the WAN link being
used. Effectively, any WAN link switch causes very small outages during switchover
while keeping all IP connections alive.
Moreover, NetModule routers also support NAT-Traversal for mobile nodes running
behind a firewall (performing NAT), which makes mobile nodes even there accessible
from a central office via their home address, and thus, bypassing any complicated VPN
setups.
The
home agent
accomplishes this by establishing a tunnel (similar to a VPN tunnel)
between itself and the
mobile node
. WAN link switching works by telling the
home
agent
that the WAN IP address (called the
care-of address
in MIP terms) of the
mobile node
has changed. The
home agent
will then encapsulate packets destined to
a
mobile node
’s home address into a tunnel packet containing the current
care-of
address
of the
mobile node
as its destination address.
To prevent problems with firewalls and private IP addressing, the MIP implementation
always employs reverse tunneling, which means that all traffic sent by a
mobile node
is
relayed via the tunnel to the
home agent
instead of directly being conveyed to the final
destination. This fact also empowers MIP to be used as a lightweight VPN replacement
(without payload secrecy).
The MIP implementation supports RFCs 3344, 5177, 3024 and 3519. For applications
requiring vast numbers of mobile nodes, interoperability with the Cisco 2900 Series
home
agent
implementation has been verified. However, since NetModule routers implement
a
mobile node
as well as a
home agent
, a MIP network with up to 10 mobile nodes
can be implemented without requiring expensive third party routers.
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