R1#conf t Enter configuration commands, one per line. End with CNTL/Z. R1(config)#int f0/1 R1(config-if)#ip proxy-arp R1(config-if)#^Z R1# *Mar 4 03:54:09.886: %SYS-5-CONFIG_I: Configured from console by console R1#sh run | i proxy
Proxy ARP enabled by default.
R1#conf t Enter configuration commands, one per line. End with CNTL/Z. R1(config)#int f0/1 R1(config-if)#no ip proxy-arp R1(config-if)#^Z R1# *Mar 4 03:54:28.566: %SYS-5-CONFIG_I: Configured from console by console R1#sh run | i proxy no ip proxy-arp R1#sh run int f0/1 Building configuration... Current configuration : 112 bytes ! interface FastEthernet0/1 ip address 172.16.1.1 255.255.255.0 no ip proxy-arp duplex auto speed auto end
Configure ASW101, ASW3 for check how Proxy ARP Configuration works, and Verification.
ASW3
Oops no configuration on ASW3. configure switch vlan1 ip address and default-gateway only. rest of configuration is see start.
Switch>en Switch#conf t Enter configuration commands, one per line. End with CNTL/Z. Switch(config)#hostname ASW3 ASW3(config)# ASW3(config)#int vlan1 ASW3(config-if)#ip addr 172.16.3.3 255.255.255.0 ASW3(config-if)#no shut ASW3(config-if)#exit ASW3(config)#ip 07:22:06: %LINK-3-UPDOWN: Interface Vlan1, changed state to up 07:22:07: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to ASW3(config)#ip defau ASW3(config)#ip default-gateway 172.16.3.2 ASW3(config)#^Z ASW3# 07:22:33: %SYS-5-CONFIG_I: Configured from console by console ASW3#sh run | i default ip default-gateway 172.16.3.2
ASW101
set ip, no default-gateway.
ASW101>en ASW101#conf t Enter configuration commands, one per line. End with CNTL/Z. ASW101(config)#int vlan1 ASW101(config-if)#ip addr 172.16.1.101 255.255.0.0 ASW101(config-if)#no shut ASW101(config-if)#^Z ASW101# *Mar 1 07:23:02.340: %SYS-5-CONFIG_I: Configured from console by console ASW101#conf t Enter configuration commands, one per line. End with CNTL/Z. ASW101(config)#^Z ASW101# *Mar 1 07:23:17.339: %SYS-5-CONFIG_I: Configured from console by console ASW101#sh run | i default
no ip proxy-arp
ASW101 think 172.16.3.3 exists same subnet.
ARP Request 172.16.3.3 but no reply.
because of no ip proxy-arp
.
ASW101#ping 172.16.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.3.3, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) ASW101#sh ip arp Protocol Address Age (min) Hardware Addr Type Interface Internet 172.16.1.101 - 001a.a10c.d3c0 ARPA Vlan1
let's configure R1 f0/1 ip proxy-arp
R1#conf t Enter configuration commands, one per line. End with CNTL/Z. R1(config)#int f0/1 R1(config-if)#ip pro R1(config-if)#ip proxy-ar R1(config-if)#ip proxy-arp R1(config-if)#^Z R1# *Mar 4 05:03:12.822: %SYS-5-CONFIG_I: Configured from console by console ASW101#ping 172.16.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.3.3, timeout is 2 seconds: .!!!! Success rate is 80 percent (4/5), round-trip min/avg/max = 1/3/9 ms
ping successful. and has no default-gateway arp entry. ASW101 shows 172.16.3.3 arp entry. but MAC addr is R1's f0/1 own address.
ASW101#sh ip arp Protocol Address Age (min) Hardware Addr Type Interface Internet 172.16.1.101 - 001a.a10c.d3c0 ARPA Vlan1 Internet 172.16.3.3 0 001b.2a77.66d3 ARPA Vlan1
then set correct subnet mask. but no default-gateway
ASW101#conf t Enter configuration commands, one per line. End with CNTL/Z. ASW101(config)#int vlan1 ASW101(config-if)#ip addr 172.16.1.101 255.255.255.0 ASW101(config-if)#^Z ASW101# *Mar 1 07:30:33.647: %SYS-5-CONFIG_I: Configured from console by console ASW101#ping 172.16.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/205/1007 ms
but still success ping…
let's clear arp table entry.
ASW101#sh ip arp Protocol Address Age (min) Hardware Addr Type Interface Internet 172.16.1.101 - 001a.a10c.d3c0 ARPA Vlan1 Internet 172.16.3.3 0 001b.2a77.66d3 ARPA Vlan1 ASW101#clea ASW101#clear ip arp % Incomplete command. ASW101#clear ip arp ASW101#clear ip arp ? A.B.C.D IP address of dynamic ARP entry inspection Clear State of ARP Inspection poll IP ARP host polling ASW101#clear ip arp 172.16.3.3 ASW101#sh ip arp Protocol Address Age (min) Hardware Addr Type Interface Internet 172.16.1.101 - 001a.a10c.d3c0 ARPA Vlan1 ASW101#ping 172.16.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/203/1007 ms ASW101#sh ip arp Protocol Address Age (min) Hardware Addr Type Interface Internet 172.16.1.101 - 001a.a10c.d3c0 ARPA Vlan1 Internet 172.16.3.3 0 001b.2a77.66d3 ARPA Vlan1
hmmm, R1 still reply arp request.
ASW101#sh int vlan1 | i address Hardware is EtherSVI, address is 001a.a10c.d3c0 (bia 001a.a10c.d3c0) Internet address is 172.16.1.101/24
ok, then disable proxy arp
R1#conf t Enter configuration commands, one per line. End with CNTL/Z. R1(config)#int f0/1 R1(config-if)#no ip proxy-arp R1(config-if)#^Z R1# *Mar 4 05:12:55.782: %SYS-5-CONFIG_I: Configured from console by console
Then, correct subnet mask no default-gateway ASW101 172.16.3.3 arp etnry exist.
ASW101#sh ip arp Protocol Address Age (min) Hardware Addr Type Interface Internet 172.16.1.101 - 001a.a10c.d3c0 ARPA Vlan1 Internet 172.16.3.3 3 001b.2a77.66d3 ARPA Vlan1 ASW101#ping 172.16.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/9 ms
still ping success let's go clear ASW101 172.16.3.3 arp etnry.
ASW101#clear ip arp 172.16.3.3 ASW101#sh ip arp Protocol Address Age (min) Hardware Addr Type Interface Internet 172.16.1.101 - 001a.a10c.d3c0 ARPA Vlan1 ASW101#ping 172.16.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.3.3, timeout is 2 seconds: ..... Success rate is 0 percent (0/5)
ping failed!
ok final step.
set default-gateway on ASW101
ASW101(config)#int vlan1 ASW101(config-if)#exit ASW101(config)#ip defau ASW101(config)#ip default-gateway 172.16.1.1 ASW101(config)#^Z ASW101# *Mar 1 07:38:41.461: %SYS-5-CONFIG_I: Configured from console by console ASW101#sh run | i default ip default-gateway 172.16.1.1 ASW101#ping 172.16.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/203/1007 ms
ping success.
let's show ASW101 arp table.
ASW101#sh ip arp Protocol Address Age (min) Hardware Addr Type Interface Internet 172.16.1.1 0 001b.2a77.66d3 ARPA Vlan1 Internet 172.16.1.101 - 001a.a10c.d3c0 ARPA Vlan1
we can be seen default gateway's ARP Entry exists.
this is correct behavior.