Random static routing issue on HP 3500/6600

[stlm]

Hi VainFox,

actually the drops (when they happen, as they are very random) I see are from the tests I run, and only when the routing is still not fully functional between 2 hosts. Once the routing is properly established, there are no drops.

That means the drops only happen in the first pings, then the rest are ok.

Is a very strange issue... 

[stlm]

Hello,

sorry to come back to this, but this still baffles me.

Yesterday night it happened again, but this time I was able to catch it.

host-a in LAN-1 sends a ping req to host-b in LAN-2.

I see the ICMP req in host-a sniffer, as well as in the router, but host-b doesn't get the ping req (no req entry for that host in the sniffer).

Does this mean that the router is not forwarding those single ICMP req, although it "sees" the packet?

If that's the case, I might see some Tx Drops on the interface to LAN-2 ( where host-b is), right?

But, I only see Tx Drops on the interface that goes to LAN-1 (where host-a is).

The interface in LAN-2 has 0 TX drops...

Still, could it be the router itself, even whe it sees the ICMP req, that is not forwarding it to the right interface?
again, this happened only once in the last 4-5 days... and for only one single source host to a single host...

[-Alex-]

Hello stlm,

On which router the routing is performed? Is it on one or routing for one vlan is on one router but the routing for the other vlan is on another router? If you have two routers maybe both should be checked. Also do you see the arp on the hosts and routers do they have the proper records in arp table? 

[stlm]

Hello Alex,

there's is basically one router  (LAN A) that connects to 3 different networks (B, C, D).

LAN B is routed via another router, that also has an IP in LAN A.

LAN C is routed via another router, that has a VLAN (only seen by the 2 routers) for the link between LAN A and LAN C.

LAN D is routed using the same router in LAN A, as this router has an IP from LAN D

So there are different scenarios. And at some point, I saw the same issue on all (one at a time).

ARP looks fine, but as the issue is random, I can't say for sure that at the very moment the issue happened, the arp was there... but the test I run involve multiple hosts, and 99% of the time when the issue occurs, there's only one that fails, the rest are just fine. Also at some point I manually added the ARP entry between the routers... but the issue was still there.

Regards,