Mobile Ip - NetModule NB2700 User Manual

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.
If MIP is run as a mobile node, the following settings can be configured:
Primary home agent address: The address of the primary home agent
Secondary home agent address: The address of the secondary home agent. The mo-
bile node will try to register with this home agent, if the primary home agent is
not reachable.
Home address: The permanent home address of the mobile node which can be used
to reach the mobile router at any time
SPI: The Security Parameter Index (SPI) identifying the security context for the mo-
bile IP tunnel between the mobile node and the home agent. This is used to
distinguish mobile nodes from each other. Therefore each mobile node needs to be
assigned a unique SPI. This is a 32-bit hexadecimal value.
Authentication type: The used authentication algorithm. This can be prefix-suffix-
md5 (default for MIP) or hmac-md5.
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