IP cache flow

Question

Hello All,
We are facing a strange issue. In the cache flow output we seeing the input interface as Te8/6 for the IP 10.57.55.11. whereas if we sh route to the same  it is taking anonther interface.
#sh ip cache verbose flow | i 10.64.2.191
Te8/6            10.57.55.11      Te7/5            10.64.2.191     06 00  00       4
Te8/6            10.57.55.11      Te7/5            10.64.2.191     06 00  00       4
#sh ip route 10.57.55.11
Routing entry for 10.57.55.0/24
  Known via "ospf 1", distance 110, metric 21, type intra area
  Last update from 10.57.0.38 on TenGigabitEthernet7/3, 1w3d ago
  Routing Descriptor Blocks:
* 10.57.0.38, from 10.57.254.142, 1w3d ago, via TenGigabitEthernet7/3
      Route metric is 21, traffic share count is 1
    10.57.0.26, from 10.57.254.142, 1w3d ago, via TenGigabitEthernet8/3
      Route metric is 21, traffic share count is
Can anybody explain the logic behind this,
Regards,
Thiyagu

Answer 1

Hi,
some kind of an asymmetric routing probably in your network.
I.e., the  10.57.55.11 source is using a different path to reach the destination 10.64.2.191 than your router would choose for routing back.
Do you see any returning traffic in your flow cache?
If not, the real returning traffic is not routed via this particular router, i.e., taking a completely different path.
Best regards,
Milan