Summary of the problem This problem is in a compute node, not in a VM. Once a VM is running in a compute node, all outbound connections in a compute node (not VM) are blocked. For example: # telnet www.google.com 80 Trying 172.217.5.4... Technical Details: We only use provider network. These 4 services are running in each compute node: - neutron-linuxbridge-agent.service - neutron-dhcp-agent.service - neutron-metadata-agent.service - openstack-nova-compute.service Detailed description of the problem: In a compute node, the following is the result of iptables -L when no VM is running: <begin> Chain INPUT (policy ACCEPT) target prot opt source destination neutron-linuxbri-INPUT all -- anywhere anywhere And our usual rules Chain FORWARD (policy ACCEPT) target prot opt source destination neutron-filter-top all -- anywhere anywhere neutron-linuxbri-FORWARD all -- anywhere anywhere Chain OUTPUT (policy ACCEPT) target prot opt source destination neutron-filter-top all -- anywhere anywhere neutron-linuxbri-OUTPUT all -- anywhere anywhere Chain neutron-filter-top (2 references) target prot opt source destination neutron-linuxbri-local all -- anywhere anywhere Chain neutron-linuxbri-FORWARD (1 references) target prot opt source destination ACCEPT all -- anywhere anywhere PHYSDEV match --physdev-out tapb --physdev-is-bridged ACCEPT all -- anywhere anywhere PHYSDEV match --physdev-in tapb --physdev-is-bridged ACCEPT all -- anywhere anywhere PHYSDEV match --physdev-out tap9 --physdev-is-bridged ACCEPT all -- anywhere anywhere PHYSDEV match --physdev-in tap9 --physdev-is-bridged Chain neutron-linuxbri-INPUT (1 references) target prot opt source destination Chain neutron-linuxbri-OUTPUT (1 references) target prot opt source destination Chain neutron-linuxbri-local (1 references) target prot opt source destination Chain neutron-linuxbri-sg-chain (0 references) target prot opt source destination ACCEPT all -- anywhere anywhere Chain neutron-linuxbri-sg-fallback (0 references) target prot opt source destination DROP all -- anywhere anywhere </end> In the same compute node, when a VM is running, the following is the result of iptables -L: <begin> Chain INPUT (policy ACCEPT) target prot opt source destination neutron-linuxbri-INPUT all -- anywhere anywhere And our usual rules Chain FORWARD (policy ACCEPT) target prot opt source destination neutron-filter-top all -- anywhere anywhere neutron-linuxbri-FORWARD all -- anywhere anywhere Chain OUTPUT (policy ACCEPT) target prot opt source destination neutron-filter-top all -- anywhere anywhere neutron-linuxbri-OUTPUT all -- anywhere anywhere Chain neutron-filter-top (2 references) target prot opt source destination neutron-linuxbri-local all -- anywhere anywhere Chain neutron-linuxbri-FORWARD (1 references) target prot opt source destination neutron-linuxbri-sg-chain all -- anywhere anywhere PHYSDEV match --physdev-out tap8 --physdev-is-bridged neutron-linuxbri-sg-chain all -- anywhere anywhere PHYSDEV match --physdev-in tap8 --physdev-is-bridged ACCEPT all -- anywhere anywhere PHYSDEV match --physdev-out tapb --physdev-is-bridged ACCEPT all -- anywhere anywhere PHYSDEV match --physdev-in tapb --physdev-is-bridged ACCEPT all -- anywhere anywhere PHYSDEV match --physdev-out tap9 --physdev-is-bridged ACCEPT all -- anywhere anywhere PHYSDEV match --physdev-in tap9 --physdev-is-bridged Chain neutron-linuxbri-INPUT (1 references) target prot opt source destination neutron-linuxbri-o8 all -- anywhere anywhere PHYSDEV match --physdev-in tap8 --physdev-is-bridged Chain neutron-linuxbri-OUTPUT (1 references) target prot opt source destination Chain neutron-linuxbri-i8 (1 references) target prot opt source destination RETURN all -- anywhere anywhere state RELATED,ESTABLISHED RETURN udp -- anywhere fermicloud248.fnal.gov udp spt:bootps dpt:bootpc RETURN udp -- anywhere 255.255.255.255 udp spt:bootps dpt:bootpc RETURN icmp -- anywhere anywhere RETURN tcp -- fermilab-net.fnal.gov/16 anywhere tcp dpt:ssh RETURN all -- anywhere anywhere match-set NIPv41d69ba3c-68e3-414f-8f1b- src DROP all -- anywhere anywhere state INVALID neutron-linuxbri-sg-fallback all -- anywhere anywhere Chain neutron-linuxbri-local (1 references) target prot opt source destination Chain neutron-linuxbri-o8 (2 references) target prot opt source destination RETURN udp -- default 255.255.255.255 udp spt:bootpc dpt:bootps neutron-linuxbri-s8 all -- anywhere anywhere RETURN udp -- anywhere anywhere udp spt:bootpc dpt:bootps DROP udp -- anywhere anywhere udp spt:bootps dpt:bootpc RETURN all -- anywhere anywhere state RELATED,ESTABLISHED RETURN tcp -- anywhere anywhere tcp dpt:https RETURN all -- anywhere anywhere RETURN tcp -- anywhere anywhere tcp dpt:http DROP all -- anywhere anywhere state INVALID neutron-linuxbri-sg-fallback all -- anywhere anywhere Chain neutron-linuxbri-s8 (1 references) target prot opt source destination RETURN all -- fermicloud248.fnal.gov anywhere MAC FA:16: DROP all -- anywhere anywhere Chain neutron-linuxbri-sg-chain (2 references) target prot opt source destination neutron-linuxbri-i8 all -- anywhere anywhere PHYSDEV match --physdev-out tap8 --physdev-is-bridged neutron-linuxbri-o8 all -- anywhere anywhere PHYSDEV match --physdev-in tap8 --physdev-is-bridged ACCEPT all -- anywhere anywhere Chain neutron-linuxbri-sg-fallback (2 references) target prot opt source destination DROP all -- anywhere anywhere </end> Let me summarize the differences from when no VM running: Chain INPUT : no change Chain FORWARD: no change Chain OUTPUT : no change Chain neutron-filter-top: no change Chain neutron-linuxbri-FORWARD: Two new rules are added neutron-linuxbri-sg-chain neutron-linuxbri-sg-chain Chain neutron-linuxbri-INPUT: One new rule is added neutron-linuxbri-o8ae816b0-f Chain neutron-linuxbri-sg-chain: Two new rules are added neutron-linuxbri-i8 neutron-linuxbri-o8 Chain neutron-linuxbri-OUTPUT: no change Chain neutron-linuxbri-local: no change Chain neutron-linuxbri-sg-fallback: no change Chain neutron-linuxbri-i8: A new chain with multiple rules Chain neutron-linuxbri-o8: A new chain with multiple rules Chain neutron-linuxbri-s8: A new chain with multiple rules But now a problem arises here: All outbound connections are blocked (remember this is in a compute node, not VM): For example: # telnet www.google.com 80 Trying 172.217.5.4... When there isn't any VM running, We don't see this problem. I was wondering if I needed to create a new security group rule for the port 80 (for example) but that didn't solve the issue. Any technical advice will be appreciated, Thanks, Hyunwoo