An issue was reported in RHBZ#1665874 where the DHCP relay agent on a switch used source address that is not the IP range of any of the ctlplane network subnets. The DHCP relay have a source address that is not in any of the provisioning subnets, thus the undercloud forwards the packet out the default gateway and the asymetric filters drop the packages in the kernel.
A workaround is possible by using ``net_config_override`` override in undercloud.conf and provide a template statically defineing all the neccecarry routes.
net_config_override = /home/stack/net-config.json.template
File: /home/stack/net-config.json.template
"network_config": [
{
"type": "ovs_bridge",
"name": "br-ctlplane",
"ovs_extra": [
"br-set-external-id br-ctlplane bridge-id br-ctlplane"
],
"members": [
{
"type": "interface",
"name": "{{LOCAL_INTERFACE}}",
"primary": "true",
"mtu": {{LOCAL_MTU}},
"dns_servers": {{UNDERCLOUD_NAMESERVERS}}
}
],
"addresses": [
{
"ip_netmask": "{{PUBLIC_INTERFACE_IP}}"
}
],
"routes": [
#
# The first two are the routes to the peer ctlplane subnets
#
{
"ip_netmask": "192.168.11.0/24",
"next_hop": "192.168.24.1"
},
{
"ip_netmask": "192.168.12.0/24",
"next_hop": "192.168.24.1"
},
#
# This additional route to the DHCP relay
#
{
"ip_netmask": "192.168.254.251/32",
"next_hop": "192.168.24.1"
}
],
"mtu": {{LOCAL_MTU}}
}
]
The undercloud.conf should have a way to define additonal routes for the ctlplane interface. It also makes sense for these routes to be present on the overcloud nodes. We probably want to add a 'host_routes' option to the subnet defenitions in undercloud.conf, i.e:
[ctlplane-subnet]
local_subnet = ctlplane-subnet
cidr = 192.168.24.0/24
dhcp_start = 192.168.24.5
dhcp_end = 192.168.24.24
gateway = 192.168.24.1
inspection_iprange = 192.168.24.100,192.168.24.120
masquerade = False
host_routes = [{"destination": "192.168.254.251/32", "nexthop": "192.168.24.1"}]
Related fix proposed to branch: master
Review: https:/