ARP behavior in Linux

Asked Jan 08 '16 at 04:44

Active Jan 08 '16 at 14:56

Viewed 223 times

I have a L3 switch. Port 1 and port 2 of the switch are added to VLAN 30 and an IP address (30.0.0.1) is assigned to it.

Port1 and port2 are connected to Host1 and Host2 respectively. Host 1 and Host2 are assigned with IP as below

L3 swtich port1 (VLAN 30) --- Host 1 (30.0.0.10)

L3 swtich port2 (VLAN 30) --- Host 2 (30.0.0.20)

Now I am trying to ping host 2 from host 1. Host 1 is sending ARP request for 30.0.0.20 to the switch, In Linux of the switch for VLAN 30, I can see the ARP request, but I don't see reply or anything, I guess the Linux is just dropping the packet.

My expectation is to ping the Host 2 from Host 1, Is there anything I am missing there.

I am capturing the packets on tcpdump for the interface Vlan30, So I am getting only the tagged packet. I don't see any ARP request on Host 2. But still I am able to ping 30.0.0.1 from both hosts.

In my HOST 1 & 2, I have ARP learnt for 30.0.0.1 and default gw is 30.0.0.1. But when I initiate ping for 30.0.0.20 from Host 1(30.0.0.10), it is initiating ARP for 30.0.0.20.

edited Jan 08 '16 at 14:56

bummi

asked Jan 08 '16 at 04:44

Vasanth Kumar

Check physical layer, check your vlan tagging. Is it enabled in the vlan? Do the hosts align? Back to basics. – Citizen Jan 08 '16 at 04:51
1

Can you see the request on Host 2? Are you using `tcpdump` or `wireshark`? – ott-- Jan 08 '16 at 06:32
Is the routing activated on the switch ? See the routing table on each element. – Dom Jan 08 '16 at 07:44
Can either host ping the switch? – David Schwartz Jan 08 '16 at 08:23
Can you ping the switch itself (ie: 30.0.0.1) from either or both of the hosts? Can you inspect the switch's address tables? see if the MAC addresses of the hosts are in it. – darklion Jan 08 '16 at 08:26

ARP behavior in Linux

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