Network interface mtu does not match across cluster members-paloaltonetworks-panos

Knowledge
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Network interface mtu does not match across cluster members-paloaltonetworks-panos
none 4.0 2
#1

Network interface mtu does not match across cluster members-paloaltonetworks-panos

Vendor: paloaltonetworks

OS: panos

Description:
Indeni will identify when two devices are part of a cluster and alert if their network interface mtu are different.

Remediation Steps:
Ensure the network interface mtu setting matches across devices in a cluster.

How does this work?
This alert logs into the Palo Alto Networks firewall through api and retrieves the status of all network interfaces. In that output, it retrieves the MTU values.

Why is this important?
The MTU of an interface may be inadvertently set to a low value. It’s important to know if this happens and fix it.

Without Indeni how would you find this?
Alerting on low MTU values normally requires scripting to be done by the administrator.

panos-show-interface

Failed to fetch the data: https://bitbucket.org/indeni/indeni-knowledge/src/master/parsers/src/panw/panos/show-interface/show-interface.ind.yaml

CrossVendorClusterInterfaceMtuVsx

Failed to fetch the data: https://bitbucket.org/indeni/indeni-knowledge/src/master/rules/templatebased/crossvendor/CrossVendorClusterInterfaceMtuVsx.scala
#2

While it is a best practice to have like hardware and capabilities connected to each HA cluster member, it is entirely possible that an Interface MTU on a Passive cluster member may need to mismatch that of the primary member.

The use case where this may exist for example is where you have a secondary ISP, Metro Ethernet or MPLS provider connected to the Passive HA box ready for a failover. If that secondary provider performs better with a lower MTU or higher for that matter, you’ll either have to choose to take the lower of the two MTU’s or allow them to be mismatched. Maybe one of your links allows for jumbo frames but the secondary link does not.

Keep in mind there are reasons why Palo Alto Networks does not synchronize these settings between HA devices. For these special cases you will need to disable the rule. You should only do so for those devices though or the value will be lost for other systems when you need it most!

#3

Absolutely Brad. Another use case is during software upgrades or when there is a need to do failover for operational or maintenance reasons.