Servers can't ping Default Gateway until arp table is cleared.

[jaguilera0]

We have just changed our network infrastructure. We have one specific vlan for servers. Servers can't learn the DG mac. The Windows servers can ping other servers on the same vlan but they can't ping the DG ip address.

[Dennis Mink]

where is your DG configured?  router ? switch either way, can you ping from the DG to any of your servers?  (might need to do extended ping).  

also are your VLANs correct?

maybe set up a span port and run wireshark and see if the arp request for dg IP address actually gets received by your switch/router

otherwise add config to post

Please rate if helpful 

[jaguilera0]

Hey Dennis

The int vlan is configured on the C6807. The server is conected on a C3850. Both switches are interconnected by fiber with trunk mode on both ends.

The server can ping other servers on the same vlan but not the Default Gateway. 

If I leave a continuous ping from the server to its DG and clear de arp-cache on the C6807 the subsequent pings get to its destinations without a problem but after a while the problems presents itself again.

[Dennis Mink]

OK, so its obviously not a connectivity problem between your server and DG. I wonder if something is sending like a gratuitous arp. can you debug arp on the 3850 and see if sometime else is advertising the DG IP with an incorrect MAC. also as soon as the pings start failing, what does the arp table show for the IP address of the DG, its obvisously not the MAC of you int vlan x on your 6807?

PLease rate if helpful

[jaguilera0]

The arp table remains the same on the DG There's the registry for the server ip and mac address with the correct values.

It seems to be a BPDU Guard issue, our workaround so far is tu disable vtp pruning on the switch where the server is connected and it seems to have solved the problem. Still on observation to see it won't present again.

Thanks.

[johnd2310]

Hi,

What IOS version are you running on the 3850? Could be buggy code on the 3850.

Thanks

John

[jaguilera0]

Hey Johnd2310 

It's running IOS-XE Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version 03.06.05E RELEASE SOFTWARE (fc2)