topic Re: 8.3 Intercluster Peer - icmp unreachable in ONTAP Discussions

8.3 Intercluster Peer - icmp unreachable

thomasb82 — Thu, 05 Jun 2025 04:10:55 GMT

Hi guys,

I have difficulties setting up Intercluster peer for SnapVault on 2x 8.3 Clusters.

They are connected to each other through ipsec vpn. All IP ranges and all ports are set to allow, nothing gets blocked.

The authentication through passphrase goes instantly to "OK" but Availability goes from "pending" to "unavailable" in a few seconds.

Data&colon; interface_reachable

ICMP: unreachable

The firewall policy is default, nothing set to block.

A few thing I find very odd:

Authentication and data interface work fine - icmp not

But then icmp works fine using a normal ping or specifiing the intercluster lif itself:

CLUSTER01::> network ping -lif CLUSTER01_INTERCLUSTER_lif1 -destination 192.168.2.1 -vserver CLUSTER01

192.168.2.1 is alive

Maybe you can help me out, many thanks!

deepuj — Fri, 05 Jun 2015 10:57:24 GMT

Hi,

When we see "interface reachable" for the Data test, and "interface unreachable" for the ICMP test, it implies an MTU size conflict.

You may take a look at this KB:

Hope this helps!

Thanks

thomasb82 — Mon, 08 Jun 2015 09:51:26 GMT

Hi,

ok, sounds reasonable.

So all my interfaces are configured with 1500, expect the cluster which is set to 9000.

It`s the same on both Filers.

The interfaces on the Firewalls (Sophos UTM) that are between those Clusters are also set to 1500.

I can successfully ping the other cluster with the setting -disallow-fragmentation true and -disallow-fragmentation false.

The only thing I'm not sure about is the ISP MTU size.

But I would imagine the disallow-fragmentation setting true would kill the ping if there was the issue?!

Sorry, I'm really stuck 😞

thomasb82 — Mon, 08 Jun 2015 17:26:53 GMT

Quick update: I really had to reduce the MTU size to 1410 to get it working...

Anyway, thanks for the hint!!