ARP problem for one VLAN

[burleyman]

I am having a problem and I think it may be ARP related. I have a VLAN for printers, VLAN48, IP Addresses 204.243.148.0/24. What happens is every so often I cannot access the printer and can't even ping it. To resolve it I unplug the printers power and patch cable and power it back and then reconnect to the network and it works fine. I have also put static ARP entries in and that resolves it as well. This happens to all types of printers and not always the same ones. When I do a show ARP I see some Incompletes where the MAC address should be and they do not always correspond to the problem printers. This also only seems to happen with that one VLAN. Here is a part of the show arp output....

Protocol Address Age (min) Hardware Addr Type Interface

Internet 10.10.104.126 2 0006.5ba2.e971 ARPA Vlan104

Internet 10.13.8.24 1 001a.a0d7.1326 ARPA Vlan40

Internet 10.10.36.51 63 0017.a48c.32da ARPA Vlan36

Internet 10.10.104.127 5 0008.740b.1cfb ARPA Vlan104

Internet 204.243.148.179 0 Incomplete ARPA

Internet 10.10.104.112 2 0008.740c.4a98 ARPA Vlan104

Internet 10.10.36.60 58 001b.78bc.0a8b ARPA Vlan36

Internet 204.242.238.200 - 0021.1b83.010d ARPA Vlan238

Internet 10.13.8.22 1 001a.a0d6.f15f ARPA Vlan40

Internet 10.10.36.61 72 001b.7846.cf7b ARPA Vlan36

Internet 204.243.148.177 0 Incomplete ARPA

Internet 10.13.8.21 13 0008.740b.a01a ARPA Vlan40

Internet 10.10.36.62 55 001b.7846.2326 ARPA Vlan36

Internet 10.10.3.25 1 000f.206b.a4c9 ARPA Vlan3

Internet 10.0.1.11 0 0007.e923.ec53 ARPA Vlan10

Internet 10.10.1.1 - 0021.1b83.e0f0 ARPA Vlan1

Internet 204.243.148.170 0 Incomplete ARPA

Internet 10.10.36.37 49 0013.211a.ac2c ARPA Vlan36

Internet 10.10.104.105 5 001a.a041.8ce7 ARPA Vlan104

Internet 10.10.3.2 1 000e.7fee.41a7 ARPA Vlan3

Internet 204.243.148.169 188 0017.088b.130c ARPA Vlan48

Internet 10.10.36.38 33 0014.384d.4a00 ARPA Vlan36

Any ideas?

Thanks,

Mike

[#2]

If the Router does not get the MAC address of the destination 204.243.148.179 during the ARP request it uses 0000.0000.000 as a placeholder in the broadcast frames sent out of interface, asking which MAC address corresponds to 204.243.148.179. If we do not get an answer, the corresponding address in the show arp output is marked as incomplete.

The following URL explains ARP issue:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_tech_note09186a00800a6057.shtml#addres_pro

The following URL helps in troubleshooting ARP issues:

http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a00807347ab.shtml#troubleshoot

[bahamut1996]

Hi,

I am experiencing the same problem in a multi-VLAN environment. There exist "arp incomplete" entries for hosts belong to 3 VLANS. However host on the other VLAN are not affected by this problem.

Initially, this affected all hosts across the network which was attributed to faulty cabling. However the cabling has been replaced, the fault only occurs to 3 of 6 VLANs.

A temporary solution has been to turn the trunk port connecting the router to the switch on and off. The ARP table is restored, and polling to end devices is resumes. However after a period of a few days, the issue would pop up.

I have browse thru the links you have included, however it remains inconclusive as where the real fault lies. The ARP incomplete error is occuring on a Cisco 3825 Router with HWIC Switch port and running IOS 12.4T(15).

IP CEF is also running in the network, since the ARP table is not complete it is preventing it from establishing adjacency for the 3 VLANs affected. And there is an incrementing encapsulation failure, when the command show ip cef adjacency is issued.

Other online discussion has identified overlapping IP address as a possible contributor to this fault, however this is not the case in this situation.

Would you have any advice as to where I should looking to better identify the problem? My gut feeling is that the ARP encapsulation could be the key, the end device might not be supportive of dynamic ARP request.

cheers,

Dave