1841ARP

Unanswered Question
May 25th, 2009
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we have configured 1841 but after some time we get the arp problem and required to do clear arp.

so we debug the ARP and found the following message.

can any one help me to undersand what this means and how can we solve this ARP issues.



ARP packet debugging is on

*May 25 08:04:25.091: IP ARP: rcvd req src 130.22.236.1 00e0.4c81.86d1, dst 130.22.236.2 FastEthernet0/0

*May 25 08:04:25.091: IP ARP: sent rep src 130.22.236.2 0021.55a3.b8ac,

dst 130.22.236.1 00e0.4c81.86d1 FastEthernet0/0

*May 25 08:05:16.215: IP ARP req filtered src 192.168.0.101 001e.ec71.1686, dst 192.168.0.1 0000.0000.0000 wrong cable, interface FastEthernet0/1

*May 25 08:05:25.091: IP ARP: rcvd req src 130.22.236.1 00e0.4c81.86d1, dst 130.22.236.2 FastEthernet0/0

*May 25 08:05:25.091: IP ARP: sent rep src 130.22.236.2 0021.55a3.b8ac,

dst 130.22.236.1 00e0.4c81.86d1 FastEthernet0/0

*May 25 08:06:25.299: IP ARP: rcvd req src 130.22.236.1 00e0.4c81.86d1, dst 130.22.236.2 FastEthernet0/0

*May 25 08:06:25.299: IP ARP: sent rep src 130.22.236.2 0021.55a3.b8ac,

dst 130.22.236.1 00e0.4c81.86d1 FastEthernet0/0

*May 25 08:06:44.247: IP ARP req filtered src 192.168.0.1 0015.1761.2520, dst 192.168.0.100 0000.0000.0000 wrong cable, interface FastEthernet0/1

*May 25 08:06:49.511: IP ARP: rcvd req src 130.22.120.51 001f.d0e3.d192, dst 130.22.120.21 FastEthernet0/1

*May 25 08:06:49.511: IP ARP: sent rep src 130.22.120.21 0021.55a3.b8ad,

dst 130.22.120.51 001f.d0e3.d192 FastEthernet0/1

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mahmoodmkl Tue, 05/26/2009 - 00:02
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Hi


Do u have a routing pointing to the interface.


Thanks

Mahmood

santosh-khargotre Tue, 05/26/2009 - 01:22
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yes , routing is pointing to the interface fa0/0. the debug message is from local interface fa0/1.


we have connected fa0/0 to RF and fa0/1 is connected to the local lan.


kindly find the sh run of router.


interface FastEthernet0/0

description WIRELESS

ip address 130.22.236.2 255.255.255.252

duplex auto

speed auto

arp timeout 120

!

interface FastEthernet0/1

description LOCAL LAN

ip address 130.22.120.21 255.255.255.0

duplex auto

speed auto

arp timeout 120

ip route 172.16.105.0 255.255.255.0 fa0/0

ip route 172.16.180.0 255.255.255.0 fa0/0

patrickvanham Tue, 05/26/2009 - 02:15
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You're routing to a broadcast interface, and that can cause issues. Try changing the routing to


ip route 172.16.105.0 255.255.255.0 130.22.236.1

ip route 172.16.180.0 255.255.255.0 130.22.236.1



santosh-khargotre Tue, 05/26/2009 - 02:29
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172.16.105.0 and 172.16.180.0 is reachiable through fa0/0 which is connected to RF.


In arp we found some error as show below.

it show the wrong cable connected to the fa0/1 and fa0/1 is local lan.

192.168.0.0 seperate local lan and no dat is routed through this router or any PC have gateway of PC fa0/1.



*May 25 08:05:16.215: IP ARP req filtered src 192.168.0.101 001e.ec71.1686, dst 192.168.0.1 0000.0000.0000 wrong cable, interface FastEthernet0/1


same tpe of setup is there in our other loation and it is working fine.


Richard Burts Tue, 05/26/2009 - 03:16
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Santosh


This problem has nothing to do with your static routes (though I agree that having the static route specify the next hop is better than having it specify the interface when the inteface is FastEthernet). And the problem is not in the configuration of your router.


The problem you are experiencing is that there are devices connected on FastEthernet0/1 which are configured with invalid IP addresses of 192.168.0.1 and 192.168.0.101. Those addresses are not in the local subnet of the interface and therefore the IOS considers them as invalid and rejects them. This problem is not likely to have much impact on your router. If you want to fix the problem you need to find the devices with the invalid configuration and correct the IP addresses to be in the subnet of the interface. Is it possible that there are devices in your network configured with 2 IP addresses (one that is in the subnet and one that is outside the subnet)?


[edit] I believe that the part of the message that says wrong cable reflects the assumption that the error may have been caused when the connection from that device was connected on the wrong interface of the router and that perhaps that connection should be on the cable connected to a different interface.


HTH


Rick

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