ARP table with strange dynamic entries

Neferith · Thu Jul 13, 2017 9:15 am

Hi All,

I use CRS226-24G-2S+ with software 6.39.2. There are couple of bridge interfaces for each vlan:
bridge-vlan10 vlan10 10.2.10.0/24
bridge-vlan20 vlan 20 10.2.20.0/24
...
One of host in vlan10 is 10.2.10.20 which I can't reach form different vlans/subnets than his own. I can ping it from 10.2.10.1/24 interface but not from any other vlan.

 ping 10.2.10.20
  SEQ HOST                                     SIZE TTL TIME  STATUS                                                                                                                                                    
    0 10.2.10.20                                 56  64 2ms  
    1 10.2.10.20                                 56  64 1ms  
    2 10.2.10.20                                 56  64 1ms  
    sent=3 received=3 packet-loss=0% min-rtt=1ms avg-rtt=1ms max-rtt=2ms 

[admin@CHR-R01] > ping 10.2.10.20 interface=bridge-vlan20
  SEQ HOST                                     SIZE TTL TIME  STATUS                                                                                                                                                    
    0 10.2.10.20                                              timeout                                                                                                                                                   
    1 10.2.10.20                                              timeout                                                                                                                                                   
    2 10.2.20.1                                  84  64 944ms host unreachable                                                                                                                                          
    3 10.2.10.20                                              timeout                                                                                                                                                   
    sent=4 received=0 packet-loss=100%

I thought it's a matter of gateway on device, but it's ok. Then I noticed strange dynamic ARP entries in ARP table:

See the screen:
https://ibb.co/n38GQF

Have you ever seen such behaviour? Mikrotik is dynamically creating entry 00:00:00:00:00:00 in different vlan (20 in this case), so it's not no reachable.
Thanks for any help!

BR/Neferith

cdiedrich · Thu Jul 13, 2017 9:58 am

the interface parameter just drops the packet on the bridge. And as you stated correctly, the host to ping is in another vlan so it can't resolve the MAC address.
This is a sign that your bridges are working properly ;-)

To check your routing you might wish to try the src-address parameter instead of interface.

-Chris

Neferith · Thu Jul 13, 2017 10:47 am

Hi Chris,

You're totally right - ping with src-address works

Thank You very much for fast and professional help!

BR/Neferith

ARP table with strange dynamic entries

ARP table with strange dynamic entries

Re: ARP table with strange dynamic entries

Re: ARP table with strange dynamic entries