[c-nsp] Wierd MPLS/VPLS issue

Alexandre Snarskii snar at snar.spb.ru
Wed Nov 23 11:30:48 EST 2016


On Wed, Nov 23, 2016 at 12:04:35PM +0000, Nick Hilliard wrote:
> Simon Lockhart wrote:
> > It looks like the Nexus 92160YC-X is spotting the 4 or 6 there, assuming it's
> > an IPv4 or IPv6 header next (Wireshark makes exactly the same incorrect 
> > assumption!), trying to decode it, and failing (because it's actually an
> > Ethernet II header), and then fails to forward the packet.
> 
> wouldn't be the first time a vendor messed this up:
> 
> > https://www.nanog.org/meetings/nanog57/presentations/Tuesday/tues.general.SnijdersWheeler.MACaddresses.14.pdf

Small correction: Juniper does check if packet starting with '4x:' is indeed 
ipv4 packet and falls back to 'outer' ethernet + mpls hash if this check fails.
As a result, all eompls traffic to such address will be forwarded to the
single link of aggregate interface and may cause congestion on this link
despite there are plenty capacity on other links, but at least this does
not lead to heavy reordering..



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