Today I have noticed a strange behaviour with forwarding of IP packets while using RouterOS v7.10rc5.
I have a CCR2004 router connected to a L3 switch through two point-to-point connections using SFP+ interfaces. Each connection between the switch and the router has a /30 network address (i.e., 10.0.1.0/30 and 10.0.2.0/30, respectively). In addition, each side has two loopback interfaces: the router has 1.1.1.1/32 and 3.3.3.3/32, whereas the switch has 2.2.2.2/32 and 4.4.4.4/32. Also, both devices have routes towards the loopbacks through the directly connected networks. Everything works fine except from one important aspect.
To set IP addresses on the ports, the switch is running the "no switchport" command on each interface. When running such command I observe that all the physical interfaces of the switch share the same MAC address (D8:5B:22:02:46:93). In particular, eth-0-17 and eth-0-18 interfaces on the switch are configured as "no switchport" with IP 10.0.1.2 and IP 10.0.2.2, respectively, and share the same MAC address D8:5B:22:02:46:93.
Now, when I look at the ARP table and routing table of the CCR2004 router I see the following:
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[admin@MikroTik] > ip arp/print
Flags: D, P - PUBLISHED; C - COMPLETE
Columns: ADDRESS, MAC-ADDRESS, INTERFACE
# ADDRESS MAC-ADDRESS INTERFACE
0 DC 10.0.1.2 D8:5B:22:02:46:93 sfp-sfpplus7
1 DC 10.0.2.2 D8:5B:22:02:46:93 sfp-sfpplus8
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[admin@MikroTik] > ip route/print
Flags: D - DYNAMIC; A - ACTIVE; c, s, y - BGP-MPLS-VPN
Columns: DST-ADDRESS, GATEWAY, DISTANCE
# DST-ADDRESS GATEWAY DISTANCE
DAc 1.1.1.1/32 loopback0 0
0 As 2.2.2.2/32 10.0.1.2 1
DAc 3.3.3.3/32 loopback0 0
1 As 4.4.4.4/32 10.0.2.2 1
DAc 10.0.1.0/30 sfp-sfpplus7 0
DAc 10.0.2.0/30 sfp-sfpplus8 0
What am I missing here? Shouldn't the router send the packets to 10.0.2.0/30 using the sfp-sfpplus8 interface even though it is learning that the D8:5B:22:02:46:93 MAC address is also available through sfp-sfpplus7?
Thanks!
Pere