How to organize direct access between two interfaces?

Question

linux

Firework!
There is a CentOS 7 server with three network cards:
wan - 11.11.11.11
lan0 - 172.16.0.1/24
lan1 - 172.16.1.1/24
net.ipv4.ip_forward = 1
FirewallD manages everything

external (active)
  interfaces: wan
  sources: 
  services: http https ssh
  ports: ...
  masquerade: yes
  forward-ports:...
  icmp-blocks: timestamp-reply timestamp-request
  rich rules

internal (default, active)
  interfaces: lan0 lan1
  sources: 
  services: dhcpv6-client http https ipp-client mdns mountd nfs rpc-bind samba-client ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: timestamp-reply timestamp-request
  rich rules:

route-n

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         11.11.11.22       0.0.0.0         UG    100    0        0 wan
11.11.11.11    0.0.0.0         255.255.255.248 U     100    0        0 wan
172.16.0.0      0.0.0.0         255.255.252.0   U     0      0        0 lan0
172.16.1.0     0.0.0.0         255.255.255.0   U     0      0        0 lan1

local interfaces go "to the world" without problems
but do not have access to each other, while from, for example, 172.16.0.0/24 networks, I can only ping 172.16.1.1 and, accordingly, vice versa.
I feel like I forgot something, but I can't figure out what.
Tell me what I didn’t finish, otherwise I’ve been fighting for 2 days and I won’t get it

Answer 1

try adding
ip ra 172.16.0.0/24 dev lan0 src 172.16.0.1
ip ra 172.16.1.0/24 dev lan1 src 172.16.1.1
and check just in case that
cat /proc/sys/net/ipv4/ip_forward
will return 1

Answer 2

Gentlemen, everything turned out to be much more prosaic. It turned out that my "provider" has a private network 172.16.0.0/24, and therefore there were conflicts of ip addresses, which I did not notice due to deep inattention. After changing the subnet everything worked.