Suspecting a bad FastEthernet Interface on Router 2651XM

[YllA]

Hi all,

I've connected two routers with each other through ethernet crossover cable on fastEthernet0/1, but I can't ping R1 from R2 or vice-versa.

My R1 fa0/1 has IP address 10.5.1.1/24 and R2 fa0/1 has IP address 10.5.3.3/24. The LEDs around the ports are lighted when the cable is connected and also when I do a show IP interface brief both status and protocol are up.  When I do a 'show CDP neighbours' it doesn't show the devices connected through that port.

After some tests done on all my router interfaces, I could determine that the problem was on only fa0/1 on Router 2. Only when I connected the routers through that port I could not ping.

Now I don't know if the problem is physical or software. Does anyone know how to perform some tests on that port to see if it's a good port?

Router#show ip int b
Interface IP-Address OK? Method Status Protocol
FastEthernet0/1 10.5.3.3 YES manual up up
Router#

Router#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater

Device ID Local Intrfce Holdtme Capability Platform Port ID
Router#

Router#show interfaces fa0/1
FastEthernet0/1 is up, line protocol is up
Hardware is AmdFE, address is 0013.1a26.0961 (bia 0013.1a26.0961)
Internet address is 10.5.3.3/24
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, 100BaseTX/FX
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:09, output 00:00:09, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
212 packets input, 16926 bytes
Received 0 broadcasts, 0 runts, 2 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog
0 input packets with dribble condition detected
177 packets output, 60658 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
28 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
19 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
Router#

[Jon Marshall]

Your post is confusing. 

You say the interfaces are 10.5.1.1/24 and 10.5.2.2/24 respectively and then the output below shows 10.5.3.3/24. 

Have you tried putting both interfaces in the same IP subnet ?

Jon

[YllA]

I edited it, it's 10.5.3.3/24.

Yes both ports connected  to each other are on the same IP subnet.

[Zach8585]

Point to point connections need to be on same subnet.  You have two different subnets here as indicated with the /24:

10.5.1.0

10.5.3.0

This will not work in this configuration.

I have two suggestions, either would work in my opinion:

1) Change the subnet mask to /16 so that the sub network would be 10.5.0.0 (or)

2) change R2's interface to 10.5.1.2 or vice versa (R1's interface to 10.5.3.2)