Information Technology Reference
In-Depth Information
On Cisco routers, Phase 1 refers to the router Ethernet interfaces being configured with a
single network address and Ethernet I encapsulation, instead of with a cable-range and
Ethernet SNAP encapsulation. A Cisco router running Software Release 8.2 or later is a
Phase 2-compliant router regardless of how the interfaces are configured.
Note
Another Phase 1 and Phase 2 issue is the handling of NBP packets. Phase 1 AppleTalk has three types
of NBP packets, and Phase 2 AppleTalk has four types of NBP packets. This difference can lead to
communication problems between Phase 1 and Phase 2 routers. Table 9-3 lists the NBP packet types for
AppleTalk Phase 1 and Phase 2.
Table9-3
Comparison of Phase1 and Phase2 NBP Packet Types
Phase 1 NBP Packet
Phase 2 NBP Packet
BrRq (Broadcast Request)
BrRq (Broadcast Request)
FwdReq (Forward Request)
LkUp (Lookup)
LkUp (Lookup)
LkUp-Reply (Lookup Reply)
LkUp-Reply (Lookup Reply)
As shown in Table 9-3, Forward Request packets do not exist in Phase 1. Only Phase 2 routers know
what to do with them. Phase 1 routers that receive Forward Request packets simply drop them.
AppleTalk: Zones Missing from Chooser
Symptom: Certain zones do not appear in the Chooser. The zones are not visible from multiple
networks. In some cases, when the Chooser is opened, the zone list changes.
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