VLAN parameter meaning

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Dear All,

Could you help me expain these words for me ("total headroom inc","total encap on xmit" ,INGRESS priority mappings,  EGRESS priority mappings.

[root@ibapp network-scripts]# cat /proc/net/vlan/bond0.117
bond0.117  VID: 117      REORDER_HDR: 1  dev->priv_flags: 1
         total frames received         6165
          total bytes received       453605
      Broadcast/Multicast Rcvd         1952

      total frames transmitted         2806
       total bytes transmitted       265508
            total headroom inc            0
           total encap on xmit            0
Device: bond0
INGRESS priority mappings: 0:0  1:0  2:0  3:0  4:0  5:0  6:0 7:0
 EGRESS priority mappings:
 
 Thank you.

CD
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Responses

Jamie Bainbridge's picture Red Hat Guru 7257 points
6 December 2012 7:07 AM

These are part of struct "vlan_dev_info" in kernel source net/8021q/vlan.h, the comment above the struct reads:

 

@cnt_inc_headroom_on_tx: statistic - number of skb expansions on TX
@cnt_encap_on_xmit: statistic - number of skb encapsulations on TX

 

The first value is the amount of times the kernel has had to allocate a new skb, because there was not enough space in the existing skb to add the VLAN tag to the frame.

 

The second value is the amount of times the kernel has added a VLAN tag to a frame after that frame has left the IP stack.

CD Active Contributor 280 points
6 December 2012 7:19 AM

Thanks Mr.Jamie. Your information really helpful. So if "total encap on xmit       0" means that kernel does not added a VLAN tag to a frame and there may be something wrong with my VLAN configuration?

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