NG800
User Manual for NRSW version 4.5.0.100
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 em-
ploys 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:
Parameter
Mobile IP Configuration
Primary home agent ad-
dress
The address of the primary
home agent
Secondary home agent ad-
dress
The address of the secondary
home agent
. The mobile node will try to
register with this home agent, if the primary
home agent
is not reach-
able.
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 mobile 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 (de-
fault for MIP) or hmac-md5.
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