3Com CoreBuilder 2500 User Manual - page 76
6-6
C
HAPTER
6: R
OUTING
WITH
IPX
However, the way that the MAC header of the packet is addressed
depends on whether a router separates the sending and destination
nodes. See Figure 6-3.
Figure 6-3
IPX Packet Routing
Sending Node’s Responsibility
When sending and destination nodes have the same network number,
the sending node addresses and sends packets directly to the destination
node. If sending and destination nodes have different network numbers,
as in Figure 6-3, the sending node must find a router on its own network
segment that can forward packets to the destination node’s network
segment.
To find this router, the sending node broadcasts an RIP packet requesting
the best route to the destination node’s network number. The router that
resides on the sending node’s segment with the shortest path to the
destination segment responds to the RIP request. The router’s response
includes its network and node address in the IPX header.
After the sending node determines an intermediate router’s address, it
can send packets to the destination node.
If the sending node is a router rather than a workstation, the node’s
internal routing tables supply the destination’s network location. The
destination router does not need to broadcast an RIP request.
Network = 000000AA
Node =
000000000001
Socket = 4003
Node
Node
000000000020
000000000021
Network = 000000BB
Node =
000000000003
Socket = 0451
MAC Header
Destination Node = 000000000020
Source Node =
000000000001
IPX Header
Checksum =
FFFF
Packet length =
011E
Tranport control = 00
Packet type =
11
Dest network =
000000BB
Dest node =
000000000003
Dest socket =
0451
Source network = 000000AA
Source node =
000000000001
Source socket =
4003
Data
MAC Header
Destination Node = 000000000003
Source Node =
000000000021
IPX Header
Checksum =
FFFF
Packet length =
011E
Tranport control = 01
Packet type =
11
Dest network =
000000BB
Dest node =
000000000003
Dest socket =
0451
Source network = 000000AA
Source node =
000000000001
Source socket =
4003
Data
Sending node
Router
Destination node