The MPLS-OPS Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Fwd: Explicit Null Configuration
Milind, I have a slightly different understanding of this than what your question implies. The Null label means the label gets popped and the packet gets forwarded as IP, yes. And in this case the label will have been originated by the Penultimate Hop router, not the originating PE. But what if there are two labels, the second one being a VPN label? Then what does the Null label mean? I believe it means, in effect, "ignore this label" and deal with what follows. In the situation of an MPLS VPN, the outer label is peeled off, leaving the inner label. A PE that supports MPLS VPNs receiving such a frame will then forward the packet based on the VPN label. This VPN label will be peeled off by the PE and the packet forwarded out the appropriate interface for that specific VPN. I hope this helps a bit. Roger Williams >X-SpamCatcher-Score: 57 [XX] >X-Real-To: rogerw@nordlink.com >Resent-Date: Sat, 21 Feb 2004 05:18:08 -0500 >X-Authentication-Warning: host.secure4-hosting.net: mplsrc12 set sender to >mpls-ops-request@mplsrc.com using -f >X-Mailer: Lotus Notes Release 5.0.1a (Intl) 17 August 1999 >From: Milind Deshpande <Milind.Deshpande@relianceinfo.com> >Date: Sat, 21 Feb 2004 15:31:37 +0530 >X-MIMETrack: Serialize by Router on INFWHUB011/SVR/RIL(Release >6.5|September 26, 2003) at > 02/21/2004 03:31:41 PM >Subject: [MPLS-OPS]: Explicit Null Configuration >To: mpls-ops@mplsrc.com >Resent-From: mpls-ops@mplsrc.com >X-Mailing-List: <mpls-ops@mplsrc.com> archive/latest/6794 >X-Loop: mpls-ops@mplsrc.com >Resent-Sender: mpls-ops-request@mplsrc.com > > > > > >As per the rfc3032 - "A value of 0 represents the "IPv4 Explicit NULL >Label". This label value is only legal at the bottom of the label stack. >It indicates that the label stack must be popped, and the forwarding of the >packet must then be based on the IPv4 header" > >Q. Does it means that Explicit Null should ONLY be configured on the edge >routers in the MPLS domain (rfc 2547bis network). > >Thanks >Milind. > >------- >The MPLS-OPS Mailing List >Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml >Archive: http://www.mplsrc.com/mpls-ops_archive.shtml ------- The MPLS-OPS Mailing List Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml Archive: http://www.mplsrc.com/mpls-ops_archive.shtml |
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