Month: June 2018

Policy Based Routing resulting in no ARP replies from gateway

One might think that when applying Policy Based Routing it will not affect ARP (Address Resolution Protocol) because they are considered to be things working on different layers. PBR clearly should affect only Layer 3 routing decisions and ARP is running somewhere below layer 3.. There are many nice discussions on the internet whether ARP is a Layer2 or Layer3 protocol and some people tend to say its Layer 2,5.

As it turns out PBR can affect ARP. If you for example wish to re-route every packet originating from the 192.168.1.0/24 network and make a policy route stating that everything from source net of 192.168.1.0/24 be routed to lets say to the GW 172.16.1.1 with out specifying any port or protocol. What will happen is that, ARP requests that use broadcast work, but unicast ARP requests won’t get replies any more – at least from Check Point firewalls. So you would need to either make 2 rules stating that it would affect TCP and UDP only based on your needs or follow Check Point supports guide lines: https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk84480

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Why using VMware vMotion on an active F5 BigIP LTM VE cluster member can be a bad idea

Although F5 states that starting from version 11.5 it supports vMotion to move a BigIP LTM VE instance between physical hosts (K15003222) some times it still can cause issues even in the newer 12.x series software. To those that didn’t want to click on the link and read what F5 has to say about it here are their recommendations for using vMotion:

  • You should perform a live migration of BIG-IP VE virtual machines on idle BIG-IP VE virtual machines. Performing a live migration of the BIG-IP VE system while the virtual machine is processing application traffic may produce unexpected results, such as dropped connections.
  • Using the vMotion feature to migrate one member of a high availability (HA) pair should not cause a failover in most cases. However, F5 recommends that you thoroughly test vMotion migration for HA systems, as you may experience different results, depending on your environment.

Well having tested it I have to say that yes, moving an active member is a bad idea since it can have “nice” side effects in certain cases. I like their unexpected results statement, namely I have seen one BigIP LTM instance drop half it’s inbound connections after vMotion in a way that even after a reboot/upgrade to a newer patch level it still drops connections from certain IP addresses in a way that they don’t even show up in tcpdump and no half the connections don’t go to the standby node they just vanish.. and as soon as you force that device to standby on the other node they re-appear.  So be very careful on what you migrate during the night, as unexpected things might happen…

But atleast in my case using vMotion on the BIG-IP VE virtual machine again, this time in standby mode and then making it active again got traffic flowing normally again.

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Insane amount of IKE SA’s on a SMB device caused by DPD and errors in logs

It seems that Check Point 1400 series SMB devices don’t handle Dead Peer Detection (DPD) that well when suddenly an external partner decides to enable it on a 3rd party firewall. Namely what happens is that you end up with tens of thousands of IKE SA’s on your little Check Point box and “Traffic Selector Unacceptable” errors in your logs.

Although in my case it didn’t cause any problems besides me being unable to see the output of the “VPN TU” command , since the IKE SA’s of the DPD flooded my console and the Embedded Gaia VPN TU utility decided not to show me it’s entire output and even crashed a few times. Ended up calling the other side and telling them to disable DPD. Hope they fix DPD support in some newer software release…

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