From: Ali.Huang (zero5291@gmail.com)
Date: Mon Dec 03 2007 - 21:35:06 ART
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@gmail.com> wrote:
> Ali,
> Few things to remember:
>
> 1) In an MPLS Core, the Core routers(LSRs) forward packets based on Tags.
> 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 identified
> using a different RD(Route Distinguisher) Value.
>
> 3) The PE Routers talk to each other using MP-BGP.Multi-protocol BGP is an
> extension of BGP which can carry extended communities like route-targets,
> VPNV4 prefix's required for MPLS VPNs.
>
> 4) In MPLS VPNs, there are 2 tags involved. The inner tag is the VPN tag and
> 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 the
> VRF table and checks to see what the next hop is.The next hop would be the
> IP Address of the remote PE where the corresponding vrf exists carring the
> destination network for the packet in it's vrf table.
>
> 6) Tag-switching within the core takes the responsibility of delivering this
> packet from the source PE to the destination PE.
>
> HTH,
> Tarun
>
> On 12/3/07, Ali.Huang <zero5291@gmail.com> 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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>
>
-- THX. Ali.huang
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