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Configuring the Spanning Tree
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Comparing IP Tunnels to Mobile IP
The Internet Engineering Task Force developed RFC 2002, IP Mobility Support,
commonly referred to as mobile IP, to provide mobility for IP hosts. Mobile IP is
designed primarily to address the needs of wireless end devices that may move between
geographically separated locations.
IP tunnels technology is designed primarily to operate in local environments, where
hand-held or vehicle-mounted devices may move rapidly between access point coverage
areas on a subnet (although it is possible to attach a geographically remote subnet
through an IP tunnel). The two technologies are complimentary and may coexist. Both
protocols use similar encapsulation to forward packets to or from end devices that have
roamed away from a home IP subnet. The root access point functions much like a
mobile IP home agent; an access point attached to the remote end of an IP tunnel
functions much like a mobile IP foreign agent.
The following table summarizes the differences between IP tunnels and mobile IP.
Issue IP Tunneling Mobile IP
Software
compatibility No changes are required to existing IP
software stacks in end devices. Requires a mobile IP client software stack in
IP end devices.
Addressing
limitations for IP
end devices Requires that IP device addresses belong to
the IP home subnet. None.
Security Guest addresses are not used. Data link
security. Mobile IP authentication is required for
“guest” access to foreign subnets.
Roaming detection Data link indications facilitate fast roaming
with no added broadcast traffic. Foreign agent advertisements.
Roaming restrictions Currently, roaming is limited to a single
network that may include multiple IP subnets. None.
Roaming support for
non-IP protocols Configurable using IP filters. None.
Scalability No practical limitations using IGMP. Has no inherent limitations.
Special network
software Standard network feature. No additional
network software is required. Requires home and foreign agents located on
each network or subnetwork.