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Switching PIX causes internet outage

We have 2 identical PIX 515e firewalls.  We manually switch the cables from the active PIX to the standby PIX for maintenance.  Whenever we do this, we lose internet connectivity.

The inside interface of the PIX is connected to a 2651 router.

When this happens I can ping from the router to the inside of the PIX, I can ping from the PIX to the internet but I cannot ping from the router to the PIX.  This happens for around 15-20 minutes and then *magically* everything starts working.

I've tried clear xlate on the PIX and clear arp-cache on the router.  I've shut down interfaces on the router and reloaded the PIX.

What is happening and how do I fix it?
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RPPreacher
Asked:
RPPreacher
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1 Solution
 
decoleurCommented:
how are the devices connected together, are there any devices between the router and the firewall... and is there a reason why you do not configure the firewalls as failovers for each other?
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RPPreacherAuthor Commented:
>how are the devices connected together


Internet---PIX---Router---MPLS_Circuit
                             |
                   4506_L3_Switch


are there any devices between the router and the firewall

No.

and is there a reason why you do not configure the firewalls as failovers for each other?

No failover license, no failover cable, never been a priority and not really related to the issue.
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decoleurCommented:
fair enough, I think the issue is the arpcache but on the outside of your network. the internet device associates your public ip address with the layer2 mac address of the pix. when you swap out the pix the traffic originating from the inside is associated with the layer2 address on the outside of the pix and it is able to return but the traffic coming from the outside in has cahced the layer 2 address that it has in its cache for the route into your network.
see if there is a way to power cycle the outside internet device and what impact that has on your changes.

hope this helps,

-t
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RPPreacherAuthor Commented:
The outside internet device is a direct fiber hand off (45 MB metro-fiber SONET).  I cannot power cycle the outside.
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decoleurCommented:
I was afraid of that. To verify that it is the arp-cache of the external service provider you will need to coordinate an outage with your service provider and see if you can get them to flush the cache of the network device that you are terminated into. they could lower their arp-cache timeout but are probably not going to be willing to do that.
If this is the source of the issue that is causeing you problems, then you need to maintain mac-address continuity at layer 2 for the transitions. there are two ways to do this, first replace the uplink device with one that doesn't change when you switch firewalls, like a layer3 switch on the outside. the other would be to set up one firewall to spoof the mac address of the other. to do the mac-spoofing go into the outside interface under the interface configuration mode and set the mac address using the command mac-address. This command was introduced in 7.2(1) and should work on your firewall assuming you have the memory to run the code.

hope this helps,

-t
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decoleurCommented:
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wilsjCommented:
have you tried to clear arp on the pix?

pix#clear arp
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RPPreacherAuthor Commented:
yes
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