Zhone IMACS 8000, User Manual

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System Cards 7-41
CPU Card IP Packet Routing
7.5 IP Packet Routing
The Integrated Access System supports multipoint routing of Internet Protocol (IP) between
all of its interfaces. These are: Serial Computer Port Interface, Server card interface (service
depends on type of card), 4 nx64 interfaces, and 8 WAN interfaces using FDL or B7R time
slot 24 of a D4-framed T1 link, or the Facility Data Link (FDL) of an ESF-framed T1 link. For
E1 links IP datagrams are forwarded using time slot 31 or the SA4 (national) bit.
To use B7R, FDL, or SA4, you must make an additional selection on the associated WAN
card. For T1 links, the selection is made via the ESF/NMS RP parameter. For E1 links, it is
made via the COM/NMS RP parameter. Refer to WAN Card and B7R Card Chapters for
further information.
All packets arriving on any of the optional paths or the local port will be treated by the IP stack
as follows:
• If the packet's destination address matches that system's address, the packet is processed
locally.
• If the address is not the same, the unit will search the routing table to find a remote
address that matches the destination of the packet.
• If a match is not found for the packet, it is routed to the interface specified in the DEF
DEST field. If the default destination matches the interface the packet arrived from, the
packet is dropped.
• IP datagrams generated as a response to a request is sent back on the same interface it was
received from. For this reason, ‘ping’ may work without even though the routing table is
not set up.
Figure 7-18 shows a typical routing arrangement. Although 24 units are used in this example,
the number of remote units is unlimited except for bandwidth and link-down considerations.