H3C Technologies H3C S12500 Series Switches - Manual (Page 100)

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Basic IP forwarding on the device
Upon receiving a packet, the device uses the destination IP address of the packet to find a match from the
forwarding information base (FIB) table, and then uses the matching entry to forward the packet.
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FIB table
A device selects optimal routes from the routing table, and puts them into the FIB table. Each FIB entry
specifies the next-hop IP address and output interface for packets destined for a specific subnet or host.
For more information about the routing table, see Layer 3—IP Routing Configuration Guide.
Use the display fib command to display FIB table entries. The following example displays the entire FIB
table.
<Sysname> display fib
Destination count: 4 FIB entry count: 4
Flag:
U:Useable G:Gateway H:Host B:Blackhole D:Dynamic S:Static
R:Relay F:FRR
Destination/Mask Nexthop Flag OutInterface/Token Label
10.2.0.0/16 10.2.1.1 U GE3/0/1 Null
10.2.1.1/32 127.0.0.1 UH InLoop0 Null
127.0.0.0/8 127.0.0.1 U InLoop0 Null
127.0.0.1/32 127.0.0.1 UH InLoop0 Null
A FIB entry includes the following items:
• Destination—Destination IP address.
• Mask—Network mask. The mask and the destination address identity the destination network. A
logical AND operation between the destination address and the network mask yields the address
of the destination network. For example, if the destination address is 192.168.1.40 and the mask
255.255.255.0, the address of the destination network is 192.168.1.0. A network mask comprises
a certain number of consecutive 1s. It can be expressed in dotted decimal format or by the number
of the 1s.
• Nexthop—IP address of the next hop.
• Flag—Route flag.
• OutInterface—Output interface.
• Token—MPLS Label Switched Path index number.
• Label—Inner label.
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Displaying FIB table entries
Execute display commands in any view.