Packet Walk-Throughs
9-3
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 8540 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 8540 DSL card.
6. The 8540 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 DSL
interface is used as the next hop.
7. The 8540 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.
Management Domain Packet Walk-Through
For an 8540 DSL card and its associated RTUs, all management functions are
performed by an agent on the DSL card.
Packet Walk-Through Using an 8546 DSL Card
Service Domain Packet Walk-Through
To examine how data packets flow through the service domain, an example of
ES1 issuing a ping to NSP1 will be used. The following assumptions are made:
H A host route entry has been configured in the Hotwire RTU for ES1
H A source domain IP entry exists for the Hotwire RTU
H A static route exists between the 8546 DSL card and the Hotwire RTU
H Filtering is disabled
