Nokia M1122 User Manual
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Copyright Nokia Networks Oy
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2-7
Internal host/gateway interface
There is a special host/gateway logical IP interface within M1122
called VBRIDGE. This interface has a specific purpose in M1122. In
applications where some ATM virtual channel connections are used
for bridging IP traffic and some other ATM virtual channel
connections are used for routing IP traffic, the VBRIDGE interface
must be used instead of LAN IP address. Alternatively, this interface is
used in bridge only application when the IP address is required for
remote management purposes.
Data VCC operation
M1122 supports the following encapsulations in each ATM data
virtual channel individually:
D
RFC2684 LLC encapsulation for bridged IP (ETH-LLC)
D
RFC2684 LLC encapsulation for routed IP (IP-LLC)
D
RFC2364 Virtual circuit multiplexed PPP over AAL5 (PPP-VC)
D
RFC2364 Virtual circuit multiplexed PPP over AAL5 used to
tunnel LAN/VBRIDGE PPTP packets (TUNNELED-PPP-VC)
If an IP address is given to a virtual channel interface and bridging is
enabled at that interface, then IP data at that interface is routed and all
other protocols are bridged. The only encapsulation which allows both
bridging and routing simultaneously is ETH-LLC. For example, it is
possible to route ETH-LLC encapsulated packets and at the same time
bridge, for example, PPPoE packets (PPPoE packets are transported
directly over Ethernet frame, not within IP packets).
2.2.2
Routing
Routing is based on routing entries in a routing table. Static routes are
added via the management interface and dynamic routing is done using
RIP and RIPv2. Routing is done between the Ethernet 10Base-T
interface and the virtual channel connection (VCC) of the ATM/ADSL
interface. M1122 supports up to 8 simultaneous VCCs.
M1122 supports IGMP (Internet Group Management Protocol) proxy
receive function for IP multicast applications.
2.2.3
Bridging
Bridging is supported to provide full protocol transparency. Bridging
can be used simultaneously with IP routing. M1122 works as a
self-learning bridge supporting up to 1024 MAC addresses. Bridging