You could enable 'l2 forward' if you wana to forward packets. 2 layer forwarding need to search mac talbe and 3 layer forwarding need to transfer packets to bvi interface for routing packets.
---------- alexan --------------原始邮件-------------- 发件人："Pim van Pelt via lists.fd.io "<[email protected]>; 发送时间：2026年2月18日(星期三) 凌晨1:07 收件人："[email protected]" <[email protected]>; 主题：[vpp-dev] L2 'flooding' on egress ----------------------------------- Hoi, I have a question about 'l2 flood' on egress versus ingress. Assume the following topolgy: vpp0, bridge-doain 100 vpp1, bridge-domain 100 GigabitEthernet10/0/0 SHG 0 GigabitEthernet10/0/0 SHG 0 vxlan_tunnel0 SHG 1, L2 Learn disable < v4 > vxlan_tunnel0 SHG 1, L2 Learn disable vxlan_tunnel1 SHG 1, L2 Learn+Flood disable < v6 > vxlan_tunnel1 SHG 1, L2 Learn+Flood disable Some BUM packet (eg ARP or IP6 neighbor discovery) comes in on vpp0 Gi10/0/0 - src MAC gets learned on Gi10/0/0, this is fine (learning is on) - gets flooded to vxlan_tunnel0 (ipv4 packet A), this is fine (flooding is on) - gets flooded to vxlan_tunnel1 (ipv6 packet B), I find this questionable (flooding is off) BUM now comes in on vpp1 twice - ipv4 packet gets accepted and flooded, this is fine (flooding is on) - ipv6 packet gets dropped, this is fine (flooding is off) Looking at the packet trace on vpp0: 17:00:06:603931: l2-learn l2-learn: sw_if_index 3 dst 33:33:00:00:00:01 src 52:54:00:f0:10:03 bd_index 3 17:00:06:603932: l2-flood l2-flood: sw_if_index 3 dst 33:33:00:00:00:01 src 52:54:00:f0:10:03 bd_index 3 l2-flood: sw_if_index 3 dst 33:33:00:00:00:01 src 52:54:00:f0:10:03 bd_index 3 17:00:06:603934: l2-output l2-output: sw_if_index 14 dst 33:33:00:00:00:01 src 52:54:00:f0:10:03 data 86 dd 60 07 03 49 00 40 3a 01 fe 80 l2-output: sw_if_index 15 dst 33:33:00:00:00:01 src 52:54:00:f0:10:03 data 86 dd 60 07 03 49 00 40 3a 01 fe 80 17:00:06:611511: vxlan6-encap VXLAN encap to vxlan_tunnel1 vni 20040 (Packet B) 17:00:06:611513: vxlan4-encap VXLAN encap to vxlan_tunnel0 vni 20040 (Packet A) I am wondering, if "L2 Flooding" is off, should we be sending the packet to sw_if_index 14 (the one with flooding disabled)? No real harm is done, because on the remote side, on vpp1, the second packet is dropped: Packet A: 23:39:08:908750: vxlan4-input VXLAN decap from vxlan_tunnel0 vni 20040 next 1 error 0 23:39:08:908752: l2-input l2-input: sw_if_index 13 dst 33:33:00:00:00:01 src 52:54:00:f0:10:03 [l2-flood ] 23:39:08:908753: l2-flood l2-flood: sw_if_index 13 dst 33:33:00:00:00:01 src 52:54:00:f0:10:03 bd_index 2 23:39:08:908761: l2-output l2-output: sw_if_index 4 dst 33:33:00:00:00:01 src 52:54:00:f0:10:03 data 86 dd 60 07 03 49 00 40 3a 01 fe 80 Packet B: 23:39:08:908748: vxlan6-input VXLAN decap from vxlan_tunnel1 vni 20040 next 1 error 0 23:39:08:908752: l2-input l2-input: sw_if_index 14 dst 33:33:00:00:00:01 src 52:54:00:f0:10:03 [] 23:39:08:908753: feature-bitmap-drop feat_bitmap_drop: feature bitmap 0x00000001 23:39:08:908755: error-drop rx:vxlan_tunnel2 23:39:08:908762: drop feature-bitmap-drop: L2 feature forwarding disabled We correctly drop the packet and refuse to flood on vpp1, end to end it works, although two packets are sent. I think it may be better to drop the packets before sending them, if the interface is marked as not FLOOD. This fix itself is quite simple, but can somebody think of a reason to flood egress on L2 interfaces with the FLOOD bit disabled ? groet, Pim -- Pim van Pelt <[email protected]> PBVP1-RIPE https://ipng.ch/
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