Forwarding issues related to MACs starting with a 4 or a 6 (Was: [c-nsp] Wierd MPLS/VPLS issue)

Alexandru Suciu asuciu at arista.com
Wed Dec 7 12:19:02 UTC 2016


The root cause for that issue is most likely due to the following bug:

BUG65077 : On the DCS-7150 series, the MPLS label of a frame may be
incorrectly overwritten by a DSCP field update in the ASIC.  Fixed in
4.11.7 , 4.12.6 , 4.13.0 .

It was not related on the MAC values but rather the incorrect parsing of
the MPLS header.



On Tue, Dec 6, 2016 at 12:50 PM, Mike Jones <mike at mikejones.in> wrote:

> > MACs that didnt make it through the switch when running 4.12.3.1:
> >
> >     4*:**:**:**:**:**
> >     6*:**:**:**:**:**
> >     *4:**:**:**:**:**
> >     *6:**:**:**:**:**
> >     **:**:*B:**:6*:**
> >     **:**:*F:**:4*:**
>
> Can anyone explain the last 2 for me?
>
> I was under the impression that this bug was mainly caused by some
> optimistic attempt to detect raw IPv4 or IPv6 payloads by checking for
> a version at the start of the frame. This does not explain why it
> would be looking at the 5th octet.
>
> I also would assume that there must be something else to the last 2
> examples beyond just the B or F and 4 or 6 because otherwise it would
> match way too many addresses to have not been noticed before. Perhaps
> the full MAC address looks like some other protocol with a 4 byte
> header?
>
> Thanks,
> Mike
>



-- 
Regards,
Alexandru Suciu


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