Hello, there is a problem with ospf operation. In particular, traffic to the router is sent on the path that has the highest cost instead of the path with the lowest cost. In attachment topology.

Traffic from routers 10.255.0.254 and 10.255.0.252 to router 10.254.0.86 when the link vlan4 is off is sent correctly, through router 10.255.0.4 and the cost of the route is 30

If you enable the link vlan 4 then the traffic to the router 10.254.0.86 starts to go through the router 10.254.0.81 although the cost of this route is 50



What is the reason for the OSPF protocol?
Topology:

How is look like your routing table and LSDB of 254 and 252 routers?

During the tests and experiments it was possible to establish the following -

3 routers located in the neighborhood in the backbon zone 10.255.0.254 10.255.0.252 10.255.0.4 Other zones are connected to them

for example, zone 1.1.1.81 has a neighborhood with all 3 routers of a backbon zone through routers 10.254.0.81 and 10.254.0.86. These routers of zone 1.1.1.81 each have their own connection to the backbon zone and are interconnected (vlan4)

10.254.0.81 establishes the neighborhood with 10.255.0.254 and 10.255.0.252
10.254.0.86 establishes the neighborhood with 10.255.0.4

For all network routers, default gateway installs routers 10.255.0.252 and 10.255.0.254

At 10.255.0.4, it does not receive the default gateway from 10.255.0.254 and 10.255.0.252, but at the same time it receives it from 10.254.0.86, which in turn is connected to 10.254.0.81 which in turn receives the route as needed from 10.255.0.254 and 10.255 .0.252


If to break vlan4 that 10.255.0.4 receives default gateway from 10.255.0.254 and 10.255.0.252 as well as should be ....

Can you see the route from 252 to 86 in routing table with cost of 40? 10 + 30.

Can you see the route from 252 to 86 in routing table with cost of 40? 10 + 30.

If vlan 4 is enabled then on 10.255.0.252 route:

387 ADo dst-address=10.254.0.86/32 gateway=10.20.7.198 gateway-status=10.20.7.198 reachable via vlan3404-Krasnoe distance=110
scope=20 target-scope=10 ospf-metric=50 ospf-type=intra-area

if vlan4 disabled

387 ADo dst-address=10.254.0.86/32 gateway=10.10.10.54 gateway-status=10.10.10.54 reachable via vlan252-transportKRSN13
distance=110 scope=20 target-scope=10 ospf-metric=30 ospf-type=inter-area

vlan 252 - transport to 10.255.0.4 (was chenget today for eliminate PtMP ospf network type in backbone)

hmmm....
routing ospf as-border-router print
# ROUTERID STATE GATEWAY COST
0 10.255.0.2 intra-area 10.10.10.30 10
1 10.255.0.4 inter-area 10.10.10.25 280
2 10.255.0.252 intra-area 0
3 10.255.0.254 intra-area 10.20.6.73 10

why cost of 10.255.0.4 is 280?....why its inter-area? it's direct connect to backbone....
That explane why trafic flow over 10.254.0.81 and default route installed from 10.254.0.86 when vlan4 enabled - because intra-area routes are rpefered....But one question - WHY 10.255.0.4 became iter-area ASBR - it has direct links to 10.255.0.252 and 10.255.0.254....It must be intra-area ASBR like 10.255.0.2 for example.

Here is from 10.255.0.4:
routing ospf as-border-router print detail
0 instance=default routerid=10.255.0.2 state=intra-area
gateway=10.10.10.49,10.10.10.53
interface=vlan251-transportR1,vlan252-transportR2 cost=20

1 instance=default routerid=10.255.0.4 state=inter-area gateway=10.10.10.53
interface=vlan252-transportR2 cost=290

2 instance=default routerid=10.255.0.252 state=intra-area gateway=10.10.10.53
interface=vlan252-transportR2 cost=10

3 instance=default routerid=10.255.0.254 state=intra-area gateway=10.10.10.49
interface=vlan251-transportR1 cost=10

It is some mutation....it desides that 10.255.0.4 - metric 290....but it is he, metric must be 0 (zero))) How that possible? reboot 10.255.0.4 - don't take effect, then reboot 10.255.0.252, after that 10.255.0.4 became not ASBR...it's became ABR...intra-area with metric 10...but when i turn on vlan 4 traffic flow over 10.254.0.81. Help i can't undarstand what is wrong?