Cisco Cisco Aironet 340 Ethernet Bridges 用户指南
7 - 6 Aironet 340 Series Bridge
Agents and to determine to which network they are currently attached.
The more frequent the advertisement, the sooner the mobile node will be
aware that it has attached to a new network and start the registration/de-
registration process (if necessary). Since these are either multicast or
broadcast datagrams (see below), the Access Point must be configured
to forward these types of frames onto the RF network. We are currently
working on a scheme to allow link layer notification of re-attachment
resulting in a Router Solicitation from the mobile node. This will
prompt a unicasted Router Advertisement from the Mobile Agent to the
mobile node and allow multicast/broadcast forwarding on the Access
Point to be turned off.
The more frequent the advertisement, the sooner the mobile node will be
aware that it has attached to a new network and start the registration/de-
registration process (if necessary). Since these are either multicast or
broadcast datagrams (see below), the Access Point must be configured
to forward these types of frames onto the RF network. We are currently
working on a scheme to allow link layer notification of re-attachment
resulting in a Router Solicitation from the mobile node. This will
prompt a unicasted Router Advertisement from the Mobile Agent to the
mobile node and allow multicast/broadcast forwarding on the Access
Point to be turned off.
The PrefixLen option allows the Prefix Length extension to the Mobil-
ity Agent (router) advertisement to be enabled or disabled. This exten-
sion is used to indicate the number of bits in the subnet mask for the
Mobility Agent generating the advertisement. The presence of the Prefix
Length extension may be helpful to some mobile nodes in determining if
they have attached to a foreign network. The default value is off. (Note:
This option should be “on” for FTP TSR stacks and “off” for VxD
stacks.)
ity Agent (router) advertisement to be enabled or disabled. This exten-
sion is used to indicate the number of bits in the subnet mask for the
Mobility Agent generating the advertisement. The presence of the Prefix
Length extension may be helpful to some mobile nodes in determining if
they have attached to a foreign network. The default value is off. (Note:
This option should be “on” for FTP TSR stacks and “off” for VxD
stacks.)
RFC 2002 (Mobile IP) states that IP Routers MAY be included in the
Router Advertisement (RFC 1256) portion of the Agent Advertisement.
However, since the IP Address of the Agent itself is included in the
router list, doing so may cause some hosts to select the Mobility Agent
as its default router. In an attempt to minimize this situation, the Mobile
Agent also includes the IP Address of its default router in the list of
advertised routers with a higher “preference” value. If a host continues
to select a Mobility Agent as its default router, the Agent can be config-
ured to advertise zero routes by setting AdvertRtrs to “off”. The default
value is “on”.
Router Advertisement (RFC 1256) portion of the Agent Advertisement.
However, since the IP Address of the Agent itself is included in the
router list, doing so may cause some hosts to select the Mobility Agent
as its default router. In an attempt to minimize this situation, the Mobile
Agent also includes the IP Address of its default router in the list of
advertised routers with a higher “preference” value. If a host continues
to select a Mobility Agent as its default router, the Agent can be config-
ured to advertise zero routes by setting AdvertRtrs to “off”. The default
value is “on”.