No mac address in arp but can ping

Unanswered Question
Jul 13th, 2009

on C2950 switch, I have connected device a.b.c.d we are able to ping this device from switch but we dont have MAC address in arp table for same IP. what could be the problem.

sh arp

Internet a.b.c.d 7 0000.0000.0000 ARPA Vlan1

Note:-This is remote setup, i do have access only to switch.

Regards,

Dinesh

I have this problem too.
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Jon Marshall Mon, 07/13/2009 - 00:36

Dinesh

On what device are you running the "sh arp" ?

The 2950 is a L2 switch only so it will not have an arp entry for the connected device. You need to go onto the device that is responsible for routing the vlan and run "sh arp" there.

So the device you connected - what is it's default-gateway ?. Go onto that device and run "sh arp"

Jon

dinesh.das Mon, 07/13/2009 - 01:43

Jon,

I dont have access to that device but i am sure about IP/ default gateway is switch VLAN ip address like other device.

device connected to the int fast 0/3

CS2950_01#ping 10.210.1.225

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.210.1.225, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

CS2950_01#sh arp

Protocol Address Age (min) Hardware Addr Type Interface

Internet 10.210.1.200 - 001a.6d3b.8700 ARPA Vlan1

Internet 10.210.1.254 3 0018.b9c1.22ac ARPA Vlan1

Internet 10.210.1.225 0 0000.0000.0000 ARPA Vlan1

Internet 10.210.1.226 41 0080.6460.bbf1 ARPA Vlan1

CS2950_01#sh mac add

Mac Address Table

-------------------------------------------

Vlan Mac Address Type Ports

---- ----------- -------- -----

All 001a.6d3b.8700 STATIC CPU

All 0100.0ccc.cccc STATIC CPU

All 0100.0ccc.cccd STATIC CPU

All 0100.0cdd.dddd STATIC CPU

1 0018.b9c1.22ac DYNAMIC Fa0/1

1 0018.b9c1.22ae DYNAMIC Fa0/1

1 0019.3033.69f6 DYNAMIC Fa0/7

1 0019.3033.6b16 DYNAMIC Fa0/7

1 0019.3033.6b72 DYNAMIC Fa0/7

1 001a.2f83.69cc DYNAMIC Fa0/7

1 001a.2f83.6b50 DYNAMIC Fa0/5

1 001a.a219.9b32 DYNAMIC Fa0/6

1 0040.63ed.c99f DYNAMIC Fa0/20

1 0080.6460.bbf1 DYNAMIC Fa0/2

1 00c0.1b0a.d625 DYNAMIC Fa0/5

1 00c0.1b0a.d956 DYNAMIC Fa0/7

1 00c0.1b0a.da2e DYNAMIC Fa0/5

Total Mac Addresses for this criterion: 17

CS2950_01#sh int fast 0/3

FastEthernet0/3 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 001a.6d3b.8703 (bia 001a.6d3b.8703)

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 10Mb/s, media type is 100BaseTX

input flow-control is unsupported output flow-control is unsupported

ARP type: ARPA, ARP Timeout 04:00:00

Last input never, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

856071 packets input, 133981174 bytes, 0 no buffer

Received 15353 broadcasts (0 multicast)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 2354 multicast, 0 pause input

0 input packets with dribble condition detected

5955697 packets output, 477162524 bytes, 0 underruns

0 output errors, 0 collisions, 4 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

0 output buffer failures, 0 output buffers swapped out

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