Cisco Express Forwarding
R1#sh run | i cef ip cef no ipv6 cef R1#conf t Enter configuration commands, one per line. End with CNTL/Z. R1(config)#ip cef R1(config)#^Z R1# *Mar 4 00:30:52.783: %SYS-5-CONFIG_I: Configured from console by console R1#sh ip cef Prefix Next Hop Interface 0.0.0.0/0 no route 0.0.0.0/8 drop 0.0.0.0/32 receive 127.0.0.0/8 drop 172.16.1.0/24 attached FastEthernet0/1 172.16.1.0/32 receive FastEthernet0/1 172.16.1.1/32 receive FastEthernet0/1 172.16.1.255/32 receive FastEthernet0/1 172.16.2.0/24 attached FastEthernet0/0 172.16.2.0/32 receive FastEthernet0/0 172.16.2.1/32 receive FastEthernet0/0 172.16.2.2/32 attached FastEthernet0/0 172.16.2.250/32 attached FastEthernet0/0 172.16.2.255/32 receive FastEthernet0/0 172.16.3.0/24 172.16.2.2 FastEthernet0/0 224.0.0.0/4 drop 224.0.0.0/24 receive 240.0.0.0/4 drop 255.255.255.255/32 receive R1#sh ad R1#sh adjacency de R1#sh adjacency detail Protocol Interface Address IP FastEthernet0/0 172.16.2.2(11) 0 packets, 0 bytes epoch 0 sourced in sev-epoch 0 Encap length 14 0024C431126E001B2A7766D20800 ARP IP FastEthernet0/0 172.16.2.250(7) 0 packets, 0 bytes epoch 0 sourced in sev-epoch 0 Encap length 14 B827EB1F4500001B2A7766D20800 ARP R1#sh run | i cef ip cef no ipv6 cef
R2#sh run | i cef ip cef no ipv6 cef R2#conf t Enter configuration commands, one per line. End with CNTL/Z. R2(config)#ip cef R2(config)#^Z R2# *Mar 4 01:41:03.315: %SYS-5-CONFIG_I: Configured from console by console R2#sh ip cef Prefix Next Hop Interface 0.0.0.0/0 no route 0.0.0.0/8 drop 0.0.0.0/32 receive 127.0.0.0/8 drop 172.16.1.0/24 172.16.2.1 FastEthernet0/0 172.16.2.0/24 attached FastEthernet0/0 172.16.2.0/32 receive FastEthernet0/0 172.16.2.1/32 attached FastEthernet0/0 172.16.2.2/32 receive FastEthernet0/0 172.16.2.255/32 receive FastEthernet0/0 172.16.3.0/24 attached FastEthernet0/1 172.16.3.0/32 receive FastEthernet0/1 172.16.3.2/32 receive FastEthernet0/1 172.16.3.255/32 receive FastEthernet0/1 224.0.0.0/4 drop 224.0.0.0/24 receive 240.0.0.0/4 drop 255.255.255.255/32 receive R2#sh ad R2#sh adjacency de R2#sh adjacency detail Protocol Interface Address IP FastEthernet0/0 172.16.2.1(11) 0 packets, 0 bytes epoch 0 sourced in sev-epoch 0 Encap length 14 001B2A7766D20024C431126E0800 ARP R2#sh run | i cef ip cef no ipv6 cef
Let's ping to TFTP server on R2.
R2#ping 172.16.2.250 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.2.250, timeout is 2 seconds: .!!!! Success rate is 80 percent (4/5), round-trip min/avg/max = 1/1/4 ms R2#sh ip cef Prefix Next Hop Interface 0.0.0.0/0 no route 0.0.0.0/8 drop 0.0.0.0/32 receive 127.0.0.0/8 drop 172.16.1.0/24 172.16.2.1 FastEthernet0/0 172.16.2.0/24 attached FastEthernet0/0 172.16.2.0/32 receive FastEthernet0/0 172.16.2.1/32 attached FastEthernet0/0 172.16.2.2/32 receive FastEthernet0/0 172.16.2.250/32 attached FastEthernet0/0 172.16.2.255/32 receive FastEthernet0/0 172.16.3.0/24 attached FastEthernet0/1 172.16.3.0/32 receive FastEthernet0/1 172.16.3.2/32 receive FastEthernet0/1 172.16.3.255/32 receive FastEthernet0/1 224.0.0.0/4 drop 224.0.0.0/24 receive 240.0.0.0/4 drop 255.255.255.255/32 receive R2#sh adjac R2#sh adjacency deta R2#sh adjacency detail Protocol Interface Address IP FastEthernet0/0 172.16.2.1(11) 0 packets, 0 bytes epoch 0 sourced in sev-epoch 0 Encap length 14 001B2A7766D20024C431126E0800 ARP IP FastEthernet0/0 172.16.2.250(7) 0 packets, 0 bytes epoch 0 sourced in sev-epoch 0 Encap length 14 B827EB1F45000024C431126E0800 ARP R2#sh adjacency Protocol Interface Address IP FastEthernet0/0 172.16.2.1(11) IP FastEthernet0/0 172.16.2.250(7)
Now, 172.16.2.250 entry appeared on R2 FIB table, Adjacency table.