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Community Member

ARP and Request Timeout

I have a lan switch (3550-48) with 4 Hosts AS400 connected, and a Cisco router 2600. The Cisco router is connected via WAN link to the Enterprise IP Network. The 2600 is the default gateway for AS400 hosts.

Frecuently cannot reach the AS400 via Telnet, ping, etc. from the Enterprise IP network, But i can reach the AS400 from the 2600 router or; form his neighbor pingging from the Wan Interfase connected to the 2600.

If i clean the arp tables in the 2600 router, Now i can reach the as400 from any place of the network.

As a patch, I set the ARP TIMEOUT to 60 seconds in the 2600 router to clear arp table each 1 minute.

I will Apprieciate any comment

10 REPLIES
Community Member

Re: ARP and Request Timeout

Maybe your running some routing/arp/caching daemon on your AS400.

Community Member

Re: ARP and Request Timeout

We're having a similar problem.

We're running dual 6509 chassis. We frequently have trouble reaching various devices on our lan. The quirk is that its neighbor on the same switch/vlan, etc, can sucessfully ping something it can't. A few minutes later the situation may reverse, or not exist at all. It seems to "roam" around the network.

When a particular device can't is unable to ping another, I can get a single ping back by clearing the arp table on the pinging device. After the first response it goes back to timing out. This usually goes on for a few minutes and then may begin working again.

Speaking of AS/400 weirdness. I was telnetted in to our AS/400 from my office machine, but was unable to ping my office machine from an AS/400 command line. Weird.

Any help is appreciated.

Community Member

Re: ARP and Request Timeout

We're having a similar problem.

When I changed my AS/400 ethernet L2 protocol from SNAP to ARPA.It is solved.

Community Member

Re: ARP and Request Timeout

We are using ARPA as L2 protocol in AS400 interfases, and we had the problem.

Like a "Solution" we changed the 3550-48 switch, we installed a 2948, and the problem was solved, by the moment. I dont know if the switches has a diferent structure. Maybe the problem will be back.

Community Member

Re: ARP and Request Timeout

Did you change the L2 protocol in the AS400 Ethernet Interface or in the Switch port were the AS400 is connected?

My AS400 expert doesnt know were he can change in the AS400 parameters.

I will appreciate your response.

Community Member

Re: ARP and Request Timeout

I change the L2 protocol in the AS/400.

use AS/400 CRTLINETH command,you will find:

Ethernet standard . . . . . . . *ETHV2, *IEEE8023, *ALL

*ETHV2 is ARPA,

*IEEE8023 is SNAP

Hope it can help you .

regards.

Henry

Community Member

Re: ARP and Request Timeout

We are having the exact same problem (no AS400's involved though). We are running dual 6509's also. I heard somewhere that there is a bug with the 6509 code dealing with ARP/CEF tables getting corrupted and doing "clear ip route * " takes care of it for the moment. I need a better fix. Anyone know of the Cisco number for this bug? Or a better way to deal with the issue?

Thanks

Community Member

Re: ARP and Request Timeout

If you are a registered CCO member, try using the Software Bug Toolkit to find out if there are any issues relating to arp/cef. You should be able to find anything relating to this problem based on IOS or problem.

Community Member

Re: ARP and Request Timeout

Which IOS are you running?

What does show IP route output looks like?

Do you need IP routing on the 6500?

I had the same problem on my 6500's which I use only for layer 2 functions.

I turned ip routing (because I did not need it) which is enabled by default and the problem went away.

Hope this helps.

Purple

Re: ARP and Request Timeout

Check bug CSCdv77534 , you may be running into this .

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