From: Iamgoingtobeaccie
Date: Mon Apr 23 2007 - 15:59:19 ART
Thanks Victor. You are right..but in this case R1 is not an egress router.Its a P router which is directly connected to R5(whose loopback is 5.5.5.5 and its another P router).Since 5.5.5.5 is directly connected to R5,R5 should be sending a Implicit null tag to R1.But when the network is advertised as /32,R5 is neither sending the implicit tag nor a label to R1.So its untagged in R1's Lfib.But when R5's loopback is advertised as /24, an implicit tag is sent to R1 by R5 and hence R1's LFIB has a POP tag for 5.5.5.0/24.
Could not understand why there is a difference.Will work on it in the morning.. I am almost falling from the chair.
Victor Cappuccio <victor@ccbootcamp.com> wrote: Hi,
This is what I understand about those 2 actions in the LFIB
Untagged means the packet will be forwarded out the given interface as IP packet (0x0800). The Pop tag mean that the penultimate router labels the packet with the null label (label 3). Is an Egress LSR know now that it should not process the packet as a labeled packet, the packet should be treated as a ip packet.
thanks,
Victor Cappuccio.-
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-----Original Message-----
From: nobody@groupstudy.com on behalf of Iamgoingtobeaccie Iamgoingtobeaccie
Sent: Mon 4/23/2007 11:22
To: ccielab@groupstudy.com
Subject: MPLS
Group,
Do we have a separate list for CCIE-SP??I did subscribe to CS,but there is no response to it.
I have a basic MPLS topology with OSPF as the IGP.If I adverise the loopbacks with their default network type,their /32 network is not being assigned labels.(Untagged) When I change the network type to point-to-point,i see pop-tag is attached in the "show mpls forwarding" command which is expected.
Is there a problem with Implicit null tag for /32 networks here.
R1#sh mpls for
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
43 Untagged 5.5.5.5/32 0 Et0/0 190.1.18.5
R1#sh mpls for
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
41 Pop tag 5.5.5.5//24 0 Et0/0 190.1.18.5
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