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SG500X stack with strange HP Printer routing

Answered Question
Jul 2nd, 2013
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I'm having a weird issue with 2 HP LaserJet 400 series printers(only 2 of these series on the network, but over 20 other working printers, and plenty other devices), they're both plugged into a stack of SG500X switches, and set to static IPs with out firewall as the default gateway, since it handles all of our routing and WAN connections.


The printers work fine locally, but for the most part won't communicate across the WAN, when I restart either printer it is accessible over the WAN for a couple minutes, then no ping responses or connectivity of any kind.


So...I mirrored the port of one of the printers to my desktop, fired up Wireshark, and found that when the printer replied to the ping from the remote subnet that the switch replies back to the printer with "Destination Unreachable" so I created a route in the switch for the remote subnet to the internal interface on our firewall, and it appears to work fine now, but I still can't figure out why I needed to do this in the first place, since the printers should be using the firewall as their default gateway.


Any ideas? Thanks in advance

Correct Answer by Tom Watts about 4 years 1 month ago

Hi Steve, it just seems like something was missed on the configuration. From how I interpret your post, your switch is being used in a layer 2 fashion and all intervlan requests are routed through the firewall.


If the switch is used in layer 3 mode but your firewall is inter-vlan routing, it would be an illadvised configuration as additional routes may be needed for basic functionalities.  Any time you have a SVI on a layer 3 switch a route has to be had on the upstream router unless it knows how to send the subnet traffic by other means.


The entire post is actually weird sounding to me.


Let's take an example your routed interface is 10.1.1.1 and your printer is 10.1.1.2. If the switch is in layer 2, the IP won't matter. If the switch is in layer 3, it should have a SVI something like 10.1.1.254. If in layer 3, the printer gateway should be the SVI of the switch.


This should work from a basic layer 3 functionality as described with both scenarios.



-Tom
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Tom Watts Tue, 07/02/2013 - 19:12
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Hi Steve, does the printer have a default gateway set? And if so, please double check to ensure it corresponds correctly.



-Tom
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Steve Galambos Wed, 07/03/2013 - 04:56
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Thanks Tom


They both have the firewall(using the same IP I created the route to) set as the default gateway, and I've triple checked that it's the correct IP, there's no ping/tracert/network check utils that I can find in the printers, but they're on the same VLAN, subnet, and even on the same switch as the firewall, so I see no reason why it couldn't reach it on it's own.

Correct Answer
Tom Watts Wed, 07/03/2013 - 07:30
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  • Green, 3000 points or more

Hi Steve, it just seems like something was missed on the configuration. From how I interpret your post, your switch is being used in a layer 2 fashion and all intervlan requests are routed through the firewall.


If the switch is used in layer 3 mode but your firewall is inter-vlan routing, it would be an illadvised configuration as additional routes may be needed for basic functionalities.  Any time you have a SVI on a layer 3 switch a route has to be had on the upstream router unless it knows how to send the subnet traffic by other means.


The entire post is actually weird sounding to me.


Let's take an example your routed interface is 10.1.1.1 and your printer is 10.1.1.2. If the switch is in layer 2, the IP won't matter. If the switch is in layer 3, it should have a SVI something like 10.1.1.254. If in layer 3, the printer gateway should be the SVI of the switch.


This should work from a basic layer 3 functionality as described with both scenarios.



-Tom
Please mark answered for helpful posts

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