Chapter 8


What are the three modes of home addressing that Cisco Mobile IP supports?


Answer: The three modes of home addressing that Cisco Mobile IP supports are static addressing, static addressing with NAI, and dynamic addressing with NAI.


How does static addressing with an NAI work?


Answer: When used together, the NAI serves as the unique identifier for the Mobile Node, and the static Home Address is verified for use by that particular NAI. The Mobile Node proposes the configured Home Address as a nonzero Home Address in the RRQ message, and the Home Agent verifies that the Mobile Node can indeed use the Home Address based on its NAI. The Home Agent can accept this address or return another address in the RRP message.


A dynamic Home Address for a Mobile Node can be assigned through which of the following methods?

  1. Local pool on the Home Network

  2. DHCP on the Home Network

  3. AAA server on the Home Network

  4. All of the above


Answer: d.


Describe how dynamic Home Address assignment through local pool works.


Answer: One or more address pools are configured on the Home Agent. The Home Agent then allocates addresses from the pool on a first come, first served basis. The Mobile Node keeps the address as long as it has an active mobility binding on the Home Agent. The Mobile Node can update its binding by sending a RRQ with either the allocated address or as its Home Address. When the binding expires, the address is immediately returned to the local pool so that it can be assigned again.


What role does the Home Agent assume when allocating a Home Address through DHCP? Briefly describe how it works.


Answer: The Home Agent assumes the role of a DHCP proxy client. IOS Mobile IP leverages the existing DHCP proxy client in IOS to allow the Home Address to be allocated by a DHCP server. The Home Agent obtains an address through DHCP on behalf of the Mobile Node. The DHCP proxy client allows the Home Agent to maintain the DHCP lease by tracking the lease time for each Mobile Node and renewing the lease while that Mobile Node still has an active binding. The NAI is sent in the Client-ID option of the DHCP request and can be used by the server to provide dynamic DNS services.


What is fixed addressing?


Answer: Dynamic addressing can be truly dynamic where the Mobile Node gets a random address upon initial registration. Dynamic addressing can also allocate the Mobile Node the same IP address all the time, commonly referred to as fixed addressing.


How does a call model help in identifying scalability concerns?


Answer: Call models are generally built toward the busy hour. The idea is that humans are creatures of habit, and in many cases, our habits are similar to those around us. The hour when all users are their most active is referred to as the busy hour. From a network engineering perspective, if enough capacity exists in the busy hour, enough capacity will be available all day long.


A busy-hour profile for one or more classes of users needs to encompass which four factors?


Answer: A busy-hour profile for one or more classes of users needs to encompass number of nodes, frequency of mobility, amount of data traffic, and number of tunnels.


What extra management does Cisco Enterprise MIB provide that RFC 2006 MIB does not?


Answer: Cisco Enterprise MIB provides management of Mobile Nodes with NAI, Home Agent redundancy, and number of Mobile Nodes currently using the Mobility Agent.


What common troubleshooting issues arise in Mobile IP deployments?


Answer: Troubleshooting issues include path MTU discovery when firewalls are deployed, transport failure because of reverse path forwarding checks, traversal of NATs or firewalls, and incompatibility in implementation of security associations.

    Mobile IP Technology and Applications
    Mobile IP Technology and Applications
    ISBN: 158705132X
    EAN: 2147483647
    Year: 2005
    Pages: 124

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