3Com S7906E - Switch, Configuration Manual

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1-2
z
Discards packets with all-zero source addresses but non-broadcast destination addresses. (A
packet with source address 0.0.0.0 and destination address 255.255.255.255 might be a DHCP
packet, and thus is not discarded.)
2) If the source address of an incoming packet is found in the FIB table:
URPF does a reverse route lookup for routes to the source address of the packet. If at least one
outgoing interface of such a route matches the receiving interface, the packet passes the check.
Otherwise, the packet is rejected.
3) If the source address is not found in the FIB table:
z
If a default route is configured, URPF lets the packet pass if the outgoing interface of the default
route is the receiving interface, and otherwise rejects it.
z
If a default route is not configured, the packet is discarded.
Configuring URPF
Follow these steps to configure URPF globally:
To do... Use the command… Remarks
Enter system view system-view ––
Enable URPF check globally ip urpf strict
Required
Disabled by default.
After you enable the URPF function on an S7900E series Ethernet switch, a half reduction of route
entries may occur. For relevant information, refer to Table 1-1 .
Table 1-1 SRPUs/LPUs on which route entries half reduction may occur
SRPU model LPU model
Route entries half reduction
may occur on
LSQ1SRP1CB, LSQ1MPUA SC LPU
LSQ1SRP2XB, LSQ1SRPB,
LSQ1CGP24TSC, LSQ1SRPD,
LSQ1SRP12GB,
LSQ1CGV24PSC
z
SC LPU (with
the last two
letters of the
LPU model
being SC, such
as
LSQ1GP48SC)
z
SD LPU (with
the last two
letters of the
LPU model
being SD, such
as
LSQ1GP48SD)
z
EB LPU (with
the last two
letters of the
LPU model
being EB, such
as
LSQ1GP48EB)
SC LPU and
SRPU
SD LPU and EB
LPU (not
working in the
route extension
mode)