[c-nsp] IOS XR 4.3.4 arp inner-cos / arp outer-cos

Matt Carter matt.carter at iseek.com.au
Thu Jun 25 00:45:12 EDT 2015

Hi all,

I recently stumbled upon and had to set the following commands in order to send ARP traffic on a double tagged service to the far end with the expected CoS value of 0.

arp inner-cos 0
arp outer-cos 0

Those commands do not appear to be documented in the  IOS XR command reference anywhere and ominously googling "arp inner-cos" or "arp outer-cos" returns no results so I'm a bit dubious about relying on these undocumented commands to resolve my issue when there the googles can't find any examples or discussion surrounding it's use.

The obvious question that comes to mind is

1)      will these commands stay valid in 5.x or am I creating a rod for my own back ?

2)      Is this the proper way to ensure ARP on a Layer3 double-tagged subint will be originated/replied to with CoS 0 for the inner and outer vlans under XR ?

Your feedback most appreciated.

Kind regards,


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