H3C Technologies H3C SecPath F1000-E - Manual (Page 148)

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Enabling the ignoring of next-hop address matching
Introduction to the ignoring of next-hop address matching
Traditional PPP links are single point-to-single point, but virtual template (VT) interface-based PPP links
are typically single point-to-multiple points. For example, a VT interface on a PPPoE server may connect
multiple PPPoE client interfaces. When a PPP packet is sent out the VT interface, the server needs to obtain
the corresponding MAC address according to the next-hop IP address of the packet and encapsulate the
packet with a link-layer header before sending it out. If the next-hop IP address is not any of the peer
addresses, the server drops the packet. Take the PPPoE network shown in Figure 62 for example. When
a packet is sent out the VT interface on the PPPoE server, the server looks up the forwarding table for a
match for the next-hop IP address of the packet. If the next hop IP address is not 10.0.0.2, 10.0.0.3, or
10.0.0.4, the server drops the packet directly.
Figure 62 A PPPoE network
On the network shown in Figure 63 , Router A and Router B are connected by a PPPoA link. The IP address
of the VT interface on Router A is 12.0.0.1/24. A NAT address pool that contains IP addresses 12.0.0.2
through 12.0.0.254 is configured for the VT interface on Router B. Router A needs to send all packets
destined for IP addresses on network segment 12.0.0.0/24 to Router B. In this case, the VT interface on
Router A operates in point-to-point mode. Because Router A maintains only one next-hop address
corresponding to Router B, a large amount of packets will be dropped if Router A performs the next-hop
address matching. To address this problem, configure Router A not to perform the next-hop address
matching, thus implementing the point-to-point application of VT interfaces.