Packet Walk-Throughs
9-5
8000-A2-GB21-30
April 1998
NSP1 then issues a reply to the ping.
1. The NSP sends the ping reply packet addressed to 155.1.3.4.
2. By normal means, the packet arrives at the router.
3. Because the router has an interface with an address 155.1.3.1 (on 155.1.3
subnet), it ARPs for 155.1.3.4.
4. Because the 8546 DSL card has a host route (marked PA=y) for 155.1.3.4, it
responds to the ARP request with its own MAC address (proxy ARP).
5. Then, the ping reply is sent directly to the 8546 DSL card.
6. The 8546 DSL card then consults its routing table to identify the next hop to
forward the packet. Since a host route is defined for ES1 (route #2), the RTU
135.1.3.3 is used as the next hop.
7. The 8546 DSL card then forwards the packet over the DSL port to that RTU.
8. Upon receiving the packet, the RTU forwards the packet to its 10BaseT port
because it has a host route for ES1.
Management Domain Packet Walk-Through
To examine how data packets flow through the management domain, an example
of the DCE Manager workstation 1 (WS1) performing a ping to the Hotwire RTU
is used. The following is assumed:
H A host route to the RTU (135.1.3.4) exists on the MCC card. (This is
generated automatically.)
H A static route to WS1 (135.1.1.1) is configured on the 8546 DSL card.
In the following illustration, WS1 is connected to the same LAN as the NMS.
