Avaya Configuring ATM Half-Bridge Services Uživatelský manuál stáhnout pdf (Strana 29)

ATM Half-Bridge Overview

308611-14.00 Rev 00

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You can use the “forward to next hop” feature to improve reliability. Consider an

example where an ISP home network has two border routers: 200.1.2.3 and

200.3.4.5. If the source-based routing gateway address (next-hop address in the

traffic filter) is advertised by both border routers, then the AHB router will send

packets from the ATM-attached hosts to whichever border router has the best

route. If this border router fails or if the link goes down, then the packets are sent

to the alternate border router. The gateway address does not need to belong to a

real device because the ISP border router forwards packets based on the

destination IP address.

For information about configuring IP filters for source-based routing, see

“Configuring Traffic Filters for Source-Based Routing,” on page 3-10.

Responding to Proxy ARP Requests

By default, AHB receives ARP requests from ATM-attached hosts. When the

AHB router receives an ARP request, it responds to this request with its own

hardware address as the target MAC address. You must enable proxy ARP

separately on each circuit.

When proxy ARP is enabled, the AHB router responds to ARP requests if all of

the following conditions are true:

• The ARP request received by AHB is not a self-ARP request (that is, the host

IP address equals the target IP address or the source address equals 0.0.0.0).

• The host’s (sender) address is already in the bridge table or can be learned

from this packet (unsecure mode enabled).

• The target host address either is in the host table and has a different

circuit VPI/VCI, or the target host address is not in the bridge table.

For information about configuring proxy ARP, see “Enabling and Disabling Proxy

ARP on a Circuit” on page 3-10.

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Avaya Configuring ATM Half-Bridge Services Uživatelský manuál Strana 29