02-27-2009 08:34 AM - edited 03-04-2019 03:44 AM
We have a cisco router in another location that has both ARPA and HDLC entries. We don't use HDLC and we don't need it at all. How do I get rid of these sessions and disable them from reoccurring.
They are only coming in on serial0/0 in the interface, there is nothing to do with HDLC anywhere. I went into that interface and used the "no encapsulation HDLC" command. This didn't solve the problem.
I would like to avoid blocking specific IPs/MACs. Is there a way to completely disable HDLC on the router itself.
Any Help is appreciated.
02-27-2009 09:22 AM
Hello Ross,
HDLC is a point-to-point serial encapsulation that can be used on a serial interface. Actually Cisco implements a proprietary version that includes a protocol field.
What is unclear is where you see mixed ARPA entries and HDLC entries
and you speak of IP/MACs.
You probably have some form of bridging over the WAN serial interface I don't see other reason to learn MAC addresses on a serial interface.
So probably if this is not needed anymore you need to remove commands like
bridge-group 1
under the serial interface configuration
But be careful if bridging over serial was configured was needed in the past.
Hope to help
Giuseppe
02-27-2009 11:23 AM
Sorry I left that part out. I found those entries in with the show arp command.
02-27-2009 11:49 AM
Hello Ross,
so you mean that in a sh arp you see entries with encapsulation HDLC ?
I've never seen this
May I ask you to post a filtered version of the configuration of your router ?
What plaform ? IOS version ?
I may be missing something but you can get better help if you provide us more details
Hope to help
Giuseppe
02-27-2009 01:12 PM
Also I don't believe "no encapsulation hdlc" is the exact command you want to be using here; it's best to specifically enable a different form of serial encaps (be it frame, PPP, or whichever).
Cisco's proprietary HDLC is the default encapsulation type for their serial interfaces, so if you use a "no encapsulation {anything}" command, the interface will default back to HDLC encapsulation, no matter which encaps type you were trying to disable.
03-01-2009 04:24 AM
Is this interface doing IP or Packet over SONET? This could be the reason for having HDLC entries in your ARP cache.
http://www.tkn.tu-berlin.de/curricula/ss02/vl-bbn/Folien/SS2002-IP_over_SONET-4up.pdf
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