Subnet not in routing table

[eekman]

How is this possible?

Sw1#show ip route 10.60.1.40
% Subnet not in table

Sw1#show ip route connected
       10.0.0.0/8 is variably subnetted
C         10.60.1.0/24 is directly connected, Vlan60

[Bobby Stojceski]

Seems ok to me. You've done a show ip route for a specific IP address but routing tables show subnets. In your case the IP you've done a show ip route on is within the 10.60.1.0/24 subnet. You won't see 10.60.1.40 in the routing table unless there was a specific route to 10.60.1.40/32

[eekman]

This is true, but there must be more to it. If I do a show ip route for a network address it shows up (this is on a 3750G), just like you said. BUT, on a 6504-E I have, when i do a  show ip route for a host IP, it shows the network entry it would use to route that IP:

6504E#show ip route 10.60.1.40
Routing entry for 10.60.1.0/24
 Known via "ospf 1", distance 110, metric 1
 tag 10, type external 2, forward metric 100
 ....

Maybe directly connected routes are not shown like above since there can only be one current way to forward packets to it?

[paul driver]

Hello

By the looks of it , this prefix is being redistributed into ospf and the 6504  see it as external type 2 with a tag of 10 and metric of 1 meaning it originates from a EGP like BGP, The forward metric of 100 is the cost towards the ASBR of the ospf domain

res
Paul

[eekman]

Yes. The question is why IP addresses belonging to a directly connected subnet does not show up in the same way.

[paul driver]

Hello

Not sure I understand, what you are asking?

Directly connected is as it stated directly connected to the router/switch its attached to.

It will only so up as a host route if the prefix itself has a subnet mask of 32, otherwise it will show the classful or classless subnet

When the prefix is advertised into a routing process the others routers/switches will not see it as directly connected as it isn't?

res

Paul

[eekman]

The question is why a 3750G shows "subnet not in table", it has nothing to do with external routes, that was just another example of the type of output I expected to see. A simple lab shows more clearly what I expected to see on the 3750 switches:

! This is from IOSvL2
!
interface GigabitEthernet0/0
 switchport trunk encapsulation dot1q
 switchport mode trunk
 negotiation auto
!
interface Vlan60
 ip address 10.0.0.3 255.255.255.0

vIOS-L2-01#show ip int brief
Interface              IP-Address      OK? Method Status     Protocol   
...   
Vlan60                 10.0.0.3        YES manual up         up      


vIOS-L2-01#show ip route connected 

      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.0.0.0/24 is directly connected, Vlan60
L        10.0.0.3/32 is directly connected, Vlan60


vIOS-L2-01#show ip route 10.0.0.44
Routing entry for 10.0.0.0/24
  Known via "connected", distance 0, metric 0 (connected, via interface)
  Routing Descriptor Blocks:
  * directly connected, via Vlan60
      Route metric is 0, traffic share count is 1

[chrihussey]

If everything is set up correctly on the switch it may be a bug. I did some checking but couldn't find anything to specific to this issue. If you do a "show ip route" and look at the entire table will the connected route show?

Maybe trying a different code would be something to try too.

[eekman]

Yes, the route show up in "show ip route". Traffic is forwarded correctly.

I have not been able to replicate the output on any other device. Feels like a bug to me. IOS 12.2(44) (yes, old, I know). There also a bunch of TCAM errors in the log that might have something to do with this. More specific prefixes are not installed, it does not say why, but are covered by less specific prefixes.

[chrihussey]

Did some quick checking, 12.2(44) SE4 & SE5 are deferred releases. Not sure if it applies to you. 12.2(55) SE10 is the Cisco suggested release for stability. Might be the way to go. Good luck.

[eekman]

-

[chrihussey]

Is there a chance you could provide the switch's config? Might be helpful.

[mark.ozga]

Turn on "no ip split horizon" on the switch connecting the two routers.