Re: mpls issue posted 12/03/2007
Yeah thanks Tarun, that was a nice summary.
On 12/3/07, Ali.Huang <zero5291@xxxxxxxxx> wrote:
> Thanks Tarun,
> I found the answer when I read the book,traffic engineering with mpls.
> I use the command show ip cef x.x.x.x detail,then the output tell me
> it need import tag.
> Maybe it's mpls feature when ldp used with bgp.
> On 12/3/07, Tarun Pahuja <pahujat@xxxxxxxxx> wrote:
> > Ali,
> > Few things to remember:
> > 1) In an MPLS Core, the Core routers(LSRs) forward packets based on
> > These tags are distributed as soon as you enable tag-switching on core
> > routers.
> > 2) MPLS VPN uses the concept of VRF's. Every Customer is uniquely
> > using a different RD(Route Distinguisher) Value.
> > 3) The PE Routers talk to each other using MP-BGP.Multi-protocol BGP is
> > extension of BGP which can carry extended communities like
> > VPNV4 prefix's required for MPLS VPNs.
> > 4) In MPLS VPNs, there are 2 tags involved. The inner tag is the VPN tag
> > the outer most tag is the LDP tag used for reaching the next hop router
> > which is the remote (PE).
> > 5) When a Packet arrives from a customer's CE router , The PE looks at
> > VRF table and checks to see what the next hop is.The next hop would be
> > IP Address of the remote PE where the corresponding vrf exists carring
> > destination network for the packet in it's vrf table.
> > 6) Tag-switching within the core takes the responsibility of delivering
> > packet from the source PE to the destination PE.
> > HTH,
> > Tarun
> > On 12/3/07, Ali.Huang <zero5291@xxxxxxxxx> wrote:
> > >
> > > hi,guys,
> > > I met a confusing question when I study mpls.When one PE receives a
> > > packet,it will check the destation,and find the match entry which gets
> > > from iBGP neighbor.
> > > The PE will import label before forward the P routers.I want to know
> > > whether the PE forwards the packet based on the label of next-hop,iBGP
> > > neighbor.I didn't get any information from my materials.So I want to
> > > confirm this.
> > > --
> > > THX.
> > > Ali.huang
> > >
> > >
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