RIB to FIB when pinging

[DialerString_2]

Why is it that when pinging from the f0/0 (10.1.55.1) to a host (10.1.55.38) the ICMP reply are using RIB?  I have CEF enabled and I can understand why the icmp packet destined for .38 would use the FIB table. - Why would the responses use the RIB?

Jun  8 16:03:18.995: IP: tableid=0, s=10.1.55.1 (local), d=10.1.55.38 (FastEthernet0/0), routed via FIB

Jun  8 16:03:18.995: IP: s=10.1.55.1 (local), d=10.1.55.38 (FastEthernet0/0), len 100, sending

Jun  8 16:03:18.995:     ICMP type=8, code=0

Jun  8 16:03:18.999: IP: tableid=0, s=10.1.55.38 (FastEthernet0/0), d=10.1.55.1 (FastEthernet0/0), routed via RIB

Jun  8 16:03:18.999: IP: s=10.1.55.38 (FastEthernet0/0), d=10.1.55.1 (FastEthernet0/0), len 100, rcvd 3

Jun  8 16:03:18.999:     ICMP type=0, code=0

Jun  8 16:03:18.999: ICMP: echo reply rcvd, src 10.1.55.38, dst 10.1.55.1

Jun  8 16:03:18.999: IP: tableid=0, s=10.1.55.1 (local), d=10.1.55.38 (FastEthernet0/0), routed via FIB

Jun  8 16:03:18.999: IP: s=10.1.55.1 (local), d=10.1.55.38 (FastEthernet0/0), len 100, sending

Jun  8 16:03:18.999:     ICMP type=8, code=0

rtr-culpeper#sh ip interface

FastEthernet0/0 is up, line protocol is up

  Internet address is 10.1.55.1/24

  Broadcast address is 255.255.255.255

  Address determined by non-volatile memory

  MTU is 1500 bytes

  Helper address is not set

  Directed broadcast forwarding is disabled

  Secondary address 10.200.20.73/30

  Multicast reserved groups joined: 224.0.0.10

  Outgoing access list is not set

  Inbound  access list is not set

  Proxy ARP is enabled

  Local Proxy ARP is disabled

  Security level is default

  Split horizon is enabled

  ICMP redirects are always sent

  ICMP unreachables are always sent

  ICMP mask replies are never sent

  IP fast switching is enabled

  IP fast switching on the same interface is disabled

  IP Flow switching is enabled

  IP CEF switching is enabled

  IP CEF Flow Fast switching turbo vector

  IP multicast fast switching is enabled

  IP multicast distributed fast switching is disabled

  IP route-cache flags are Fast, Flow cache, CEF, Full Flow

  Router Discovery is disabled

  IP output packet accounting is enabled

  IP access violation accounting is disabled, system threshold is 512

  TCP/IP header compression is disabled

  RTP/IP header compression is disabled

  Policy routing is disabled

  Network address translation is disabled

  BGP Policy Mapping is disabled

  WCCP Redirect outbound is disabled

  WCCP Redirect inbound is disabled

  WCCP Redirect exclude is disabled

FYI -  I can ping this device from it's LAN, but not from another network ie 10.1.38.0. -  I can ping everything else on the 10.1.55.0 network but not that one device. It's jet direct.

thanks guy and gals.

[dominic.caron]

Hi,

It's not using the FIB because it doesnt have to forward the packet to another host. The router is the destination. The FIB is a Mtrie leaf data structure. Each leaf points to an entry in the adjacency table.

[dominic.caron]

And...Look's like a bad default gateway on the host...try enabling proxy arp just to test it.

[DialerString_2]

Thanks Dominic and the gateway was the first thing I checked and it's set correctly!!!!

[DialerString_2]

Jun  8 16:03:18.999: ICMP: echo reply rcvd, src 10.1.55.38, dst 10.1.55.1

Jun  8 16:03:18.999: IP: tableid=0, s=10.1.55.1 (local), d=10.1.55.38 (FastEthernet0/0), routed via FIB

Why does it say 'FIB' here?

[dominic.caron · Accepted solution]

The destination is not local.

[DialerString_2]

Got it and thanks, D.

[dominic.caron]

Is the netmask of the client correct?

I would realy try proxy-arp if I was you, over the years, I've stumble over a few host with bad network implementation.

[DialerString_2]

I'm going to try proxy-arp now. The all ip information is correct. 10.1.55.38/24 gw is .1... It was working early today and then the location had a power failure.