[420] in linux-net channel archive
ARP: multiple entries (possible bug)
daemon@ATHENA.MIT.EDU (Herbert Rosmanith)
Mon Jun 5 18:19:23 1995
From: Herbert Rosmanith <herp@wildsau.idv.uni-linz.ac.at>
To: linux-net@vger.rutgers.edu
Date: Mon, 5 Jun 1995 22:29:14 +0200 (MET DST)
Subject: multiple ARP entries
greetings,
is it allowed that for one IP-address more than one MAC-address is
stored in the arp table ?
it is possible to do so, see above:
>> # ifconfig eth0
>> eth0 Link encap:10Mbps Ethernet HWaddr 40:52:43:D0:0D:38
>> inet addr:140.78.40.25 Bcast:140.78.40.255 Mask:255.255.255.0
>> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
>> RX packets:1102292 errors:0 dropped:0 overruns:0
>> TX packets:1088490 errors:0 dropped:0 overruns:0
>> Interrupt:3 Base address:0x300
>>
so, my own IP address is 140.78.40.25
now we take another IP address on the same segment, say 140.78.40.62:
>> # arp -a
>> Address HW type HW address Flags Mask
>> 140.78.40.62 10Mbps Ethernet 00:C0:6C:41:42:31 C *
>> 140.78.40.31 10Mbps Ethernet 00:00:0C:08:28:37 C *
>> # ifhwaddr eth0
>> 40:52:43:d0:0d:38
>> # arp -s 140.78.40.62 `ifhwaddr eth0` 255.255.255.252 pub
>> # arp -a
>> Address HW type HW address Flags Mask
>> 140.78.40.31 10Mbps Ethernet 00:00:0C:08:28:37 C *
>> 140.78.40.62 10Mbps Ethernet 40:52:43:D0:0D:38 CMP *
okay, the first entry for 140.78.40.62 has been overridden. but not for
long, because:
>> # ping -c 1 140.78.40.62
>> PING 140.78.40.62 (140.78.40.62): 56 data bytes
>> 64 bytes from 140.78.40.62: icmp_seq=0 ttl=255 time=2.5 ms
>>
>> --- 140.78.40.62 ping statistics ---
>> 1 packets transmitted, 1 packets received, 0% packet loss
>> round-trip min/avg/max = 2.5/2.5/2.5 ms
>> # arp -a
>> Address HW type HW address Flags Mask
>> 140.78.40.62 10Mbps Ethernet 00:C0:6C:41:42:31 C *
>> 140.78.40.31 10Mbps Ethernet 00:00:0C:08:28:37 C *
>> 140.78.40.62 10Mbps Ethernet 40:52:43:D0:0D:38 CMP *
now, which MAC-address is the kernel going to take when doing ARP-lookups ?
probably, before insertion, it could do an arp_find ?
i'm not sure if this counts as bug anyway!
-------------------------------------------------------------
herp@wildsau.idv.uni-linz.ac.at | Fighting for peace is like
Rosmanith@Edvz.uni-linz.ac.at | fucking for virginity
