VLAN and ARP table

[Gleb Smirnoff]

On Tue, Sep 04, 2012 at 09:18:43AM -0400, Brad Plank wrote:
B> VLAN interfaces that have a parent interface configured with an IP 
B> address do not show up in the arp table.  If the VLAN's parent interface 
B> does not have an IP address, it will show up in the arp table.
B> [Notice the output from ifconfig below, to duplicate this issue.]
B> 
B> #ifconfig
B> em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
B> options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM>
B>          ether 08:00:27:b7:11:3b
B>          inet 10.20.13.104 netmask 0xffff0000 broadcast 10.20.255.255
B>          inet6 fe80::a00:27ff:feb7:113b%em0 prefixlen 64 scopeid 0x1
B>          inet6 2620:3f:8000:1:d::104 prefixlen 64
B>          nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
B>          media: Ethernet autoselect (1000baseT <full-duplex>)
B>          status: active
B> vlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
B>          options=3<RXCSUM,TXCSUM>
B>          ether 08:00:27:b7:11:3b
B>          inet 172.16.200.104 netmask 0xffffff00 broadcast 172.16.200.255
B>          nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
B>          media: Ethernet autoselect (1000baseT <full-duplex>)
B>          status: active
B>          vlan: 115 parent interface: em0
B> 
B> # arp -an
B> ? (10.20.13.112) at c8:60:00:c3:24:19 on em0 expires in 1182 seconds 
B> [ethernet]
B> ? (10.20.13.9) at 00:12:3f:20:b9:4c on em0 expires in 1104 seconds 
B> [ethernet]
B> ? (10.20.13.104) at 08:00:27:b7:11:3b on em0 permanent [ethernet]
B> ? (10.20.13.110) at 00:90:fb:02:db:e8 on em0 expires in 669 seconds 
B> [ethernet]
B> ? (10.20.13.109) at 08:00:27:7c:19:d5 on em0 expires in 1199 seconds 
B> [ethernet]
B> ? (10.20.254.254) at 00:00:5e:00:01:33 on em0 expires in 1179 seconds 
B> [ethernet]

Can't reproduce that on 10-current:

root at behemoth:~:|>ifconfig vlan0 create
root at behemoth:~:|>ifconfig vlan0 vlan 666 vlandev igb1 10.205.0.1/24
root at behemoth:~:|>arp -s 10.205.0.2 0:0:0:0:0:0
root at behemoth:~:|>arp -an
root at behemoth:~:|>arp -an | grep vlan  
? (10.205.0.2) at 00:00:00:00:00:00 on vlan0 permanent [vlan]
root at behemoth:~:|>

May it happen that your vlan0 really doesn't have any entries in arp cache?

-- 
Totus tuus, Glebius.