Loosing IP connection to HP network printers

[Tor-Arne Nostdal]

On a couple of our subnets we have problems with loosing IP connection towards our network printers.
To me it seems as the routers is loosing the arp entries.
If we turn off/on the printers they'll be available for a while again.
If we ping them from a PC on the same LAN they will also become visible for the WAN.

Question 1)
Could there be any other plausible cause than a router/switch issue on this ?

Question 2)
Do anyone know how HP printers announce their presence / broadcast "keep alive"

Printers: different HP network based printers (Only TCP protocol enabled - other protocols disabled) (10Mb eth. cards)
Network: Only Cisco equipment (mostly Switches with 10/100 autosense)
Printing both from Windows/Unix environment

/Tor-Arne

[Ron Kinner]

On a Cisco switch (depending on the OS) you can do

sh cam dyn
or
sh mac

and it should list all of the MAC addresses it knows and tell you what port they are on.

If you ping the printer from a Window box then do

arp -a

in cmd window you should see the MAC address of the printer which you can record and look for when it stops working.

You can put the entry in as a static entry if you like. The same goes for a router tho there the
sh arp
command will show you what macs and IP addresses it knows.

I don't think they really do anything special to stay alive. If nobody talks to them they don't really care. The next time a pc or unix bos wants to talk it will have to send out an ARP anyway since a PC only holds an ARP for 4 minutes. If the printer's MAC is no longer in the switch's forwarding database it will send the ARP request out all ports. So it should get it and reply after which the switch will know where he is.

My suspicion is that you may have a squatter on your network using the same IP address as your printer. Perhaps he's on a different switch? Try disconnecting the printer and ping the same IP address. See if anyone answers.

Ron

[OLARU Dan]

Some printers enter "powersave" mode if they are not used for 10-15 minutes. The "powersave" feature can be disabled on HP printers.

Are you using STP on your switches? This can cause 1-2 minutes delay when sending print jobs to printers that entered powersave mode.

[Tor-Arne Nostdal]

There is no IP-conflict.
We have tried to replace the network card in the printer. We have tried to vary between DHCP/Static IP-definition - no result.

There is no errors reported on the switch where the printer is attached. If we look at the port it is green and no transmission erros - everything seems fine.

I can see the arp entry for the printer(s) on the router.
If we clear the arp table on the router, it will rebuild and the printer will respond for a while.
Then after some minutes it will stop responding, but still be in the arp table.

/Tor-Arne

[Tor-Arne Nostdal]

Here's how it is connected:
Cisco Router->Catalyst 5500 Switch->Catalyst 1900 -> Printer

We could see the arp entry in the 5500 by show cam on the port where the 1900 is attached. After some minutes it dissapears.

When we did a clear arp on the router it will appear again, and we'll get connection.

If we continue to monitor the 5500 arp entries it seems to stay there as well for a long time.
After 10min. we try to ping again and it fails. It is then removed from the arp entries in the 5500 but still remain in the router.

So - we tried to define a static arp entry in the 5500. - Still it fails.

It seems that this must be a problem with the 1900 switch.

I think it works like this:
When we clear the arp from the router - it will start a broadcast to get info. During this broadcast the arp table both in the router as well as 5500 will be refreshed, and the 1900 will also be "refreshed".

When it fails, both the router and 5500 know where the printer should be, but the 1900 do not handle it.

We'll try to replace the 1900 next week...

/Tor-Arne